The Federal Democratic Republic of Ethiopia Amhara ... · Amhara region.Tana sub basin categorized under four major watersheds, namely Megech, Rib, Gumara and Gilgel Abay.The major

Tana Sub-basin Land Use Planning and Environmental Study Project

BoEPLAU Watershed Management Draft Final Report ADSWE i

The Federal Democratic Republic of Ethiopia

Amhara National Regional State

Bureau of Environmental Protection, Land Administration and Use

(BoEPLAU)


Technical Report: Watershed Management Study Draft Final

(ADSWE, LUPESP /TaSB: Section II/Volume 07/2015)

February 2015

Bahir Dar

Client:Bureau of Environmental Protection, Land Administration and Use (BoEPLAU)

Address:

P.O.Box: 145

Telephone: +251-582-265458

Fax: (058) 2265479

E-mail:Amhara [email protected]

Consultant: Amhara Design & Supervision Works Enterprise (ADSWE)

Address:

P.O.Box: 1921

Telephone: +251-582-181023/ 180638/181201/181254

Fax: (058) 2180550/0560

E-mail:amhara [email protected]

mailto:Amhara%[email protected]

mailto:amhara%[email protected]


BoEPLAU Watershed Management Study DraftFinal Report ADSWE ii

LIST OF REPORTS

Section I: MAIN REPORT

Section II: SECTOR STUDIES

Volume I: Soil Survey

Volume II: Forest and Wildlife Assessment

Volume III: Hydrology and Water Resource Assessment

Volume IV: Land Use and Land Cover

Volume V: Agro Climatic Assessment

Volume VI: Crop Resource Assessment

Volume VII: Watershed Management

Volume VIII: Livestock Production and Feed Resource

Assessment

Volume IX: Human Health Assessment

Volume X Animal Health Assessment

Volume XI: Fish and Wetland Assessment

Volume XII: Sociologic Assessment

Volume XIII: Economic Study

Volume XIV: Tourism Assessment

Section III PLANNING

Volume I Approaches, Procedures and Methods

Volume II Land Utilization Types Description and their

Environmental Requirements Setting

Volume III Planning Units Description

Volume IV Land Suitability Evaluation

Volume V Land Use Plan

Volume VI Management plan

Volume VII Implementation Guideline

SECTION IV ANNEXES

Maps albums and data base


BoEPLAU Watershed Management Study DraftFinal Report ADSWE iii

EXECUTIVE SUMMARY

Watershed is any surface area from which runoff resulting from rainfall collected and drained through a

common confluence point. Now a day‟s watershed degradation is a serious problem in the developing

country like Ethiopia. Land degradation is the decline in land quality and the results of complex

interactions between physical, chemical, biological, socioeconomics and political issues of local, national,

or global nature. Some of the causes of degradation are natural hazards, population growth, expansion of

agricultural lands forests and marginal lands, poverty, land ownership problems, political instability,

administration problems and inappropriate agricultural practice.

Tanasub basin is part of Amhara Regional State affected by the different types of land degradation such as;

water erosion and flooding are the main problem in the study area. The objective of watershed

management study is to identify and understand ecological and socio economic problems in the basin and

prepare watershed intervention plan that enable sustainable management and use of resources.

The sub basin includes about 29 rural woredas and three-townworeda of the region. The sub basin has a

total area of 1,579,096.94 hectares. It is one of the most important potential areas for all development in

Amhara region.Tana sub basin categorized under four major watersheds, namely Megech, Rib, Gumara

and Gilgel Abay.The major type of land use/cover are cultivated land, forest, shrubs and Bush land,

grassland, wetland, water bodies, afro alpine and built up areas. The method followed for this study is

collection of primary and secondary data at field level. The study approaches and procedures followed

different stages of the study include pre-field work, fieldwork, and post fieldwork activities.

Land degradation assessment is one of land resources assessment conducted on qualitative& quantitative

indicators. The soil lossmap developed on Arc GIS environment by using RUSLE parameters as an input

to assess average annual soil loss rate of the area.Based on the analysis,2833.06 ton/ha/year total amount

of soil loss in the sub basinat mountains and hilly areas and 0 ton/ha/yr where deposition takes place at flat

and level areas and the mean annual soil loss of 29 t /ha/yr.From the assessment 73.69 % of the area has

soil loss fall non to slight,14.03% moderate ,9.24 % high and 3.03% very high soil loss class respectively..

Soil and water conservation is preventing soil and water from degradation. The soil and water

conservation trend in the sub basin isbetter.

The overall impact of land degradation in the sub basin is not limited to the level of reduction of land

productivity in the upper stream areas, but rather has brought colossal impacts on the downstream areas. In

order to alleviate the problems, the study identified and presented different mitigation measures in the

main body of the report.


BoEPLAU Watershed Management Study DraftFinal Report ADSWE iv

TABLE OF CONTENT

LIST OF REPORTS ....................................................................................................................................... ii

EXECUTIVE SUMMARY ................................................................................................................................ iii

TABLE OF CONTENT ................................................................................................................................ iv

LIST OF TABLES ....................................................................................................................................... vii

LIST OF FIGURES ..................................................................................................................................... viii

ABBREVIATIONS AND ACRONYMS ...................................................................................................... ix

1. INTRODUCTION .................................................................................................................................. 1

1.1 Background ........................................................................................................................ 1

1.2 Scope of the Study.............................................................................................................. 2

1.3 Objectives of the Project .................................................................................................... 2

1.3.1 General Objective ................................................................................................................... 2

1.3.2 Specific objectives .................................................................................................................. 3

1.4 Limitation of the study ....................................................................................................... 3

2. LITERATURE REVIEW ....................................................................................................................... 4

2.1 History and Experience of Watershed Based Development .............................................. 4

2.2 Experiencein Watershed Management in Amhara Region ..................................................... 4

2.3 Baseline Survey of Community-Based Integrated Natural Resources Management Project

in Lake Tana Sub-Basin, TCS (2013) ........................................................................................... 5

2.4 Baseline Information of Community-Based Integrated Natural Resources Management

Project in Lake Tana Sub-Basin, IFAD/EPLAUA (2007) ............................................................ 6

2.5 Megech-Seraba Pump Irrigation Project ............................................................................ 7

2.6 Rib irrigation Project .......................................................................................................... 8

2.7 Koga irrigation Project ............................................................................................................ 8

2.8 Watershed Degradation ........................................................................................................... 9

2.9 Land Degradation ............................................................................................................. 10

2.10 Land Degradation Indicators ............................................................................................... 11

2.11Driving Forces, Pressure, State, Impact and Response Indicators ....................................... 11

2.11.1 BiophysicalLand Degradation Indicators .................................................................................. 12

2.11.2Socio-Economic Land Degradation Indicators ........................................................................... 12

2.12Land Degradation Assessment ............................................................................................. 13


BoEPLAU Watershed Management Study DraftFinal Report ADSWE v

2.12.1Qualitative Land degradation Assessment ................................................................................. 13

2.12.2 Quantitative Land degradation assessment ................................................................................ 16

3. MATERIALS AND METHODS ......................................................................................................... 25

3.1 Description of the Study Area .......................................................................................... 25

3.1.1 Slope ............................................................................................................................................ 28

3.1.2 Soil condition in the sub basin ..................................................................................................... 29

3.1.3 Land Use/ Cover .......................................................................................................................... 30

3.2 Materials and Equipment ................................................................................................. 31

3.3 Methodology ......................................................................................................................... 32

3.3.1 Pre Field ...................................................................................................................................... 32

3.3.2 At Field ........................................................................................................................................ 32

3.3.3 Post Field ..................................................................................................................................... 33

4. RESULT AND DISCUSSION ............................................................................................................. 37

4.1 Watershed Delineation, Morphology and characteristics ..................................................... 37

4.1.1 Watershed Delineation ................................................................................................................ 37

4.1.2 Morphology ................................................................................................................................. 38

4.1.3 Drainage Pattern .......................................................................................................................... 38

4.2 Fragility Assessment ............................................................................................................. 39

4.2.1 Climatic Fragility Assessment ..................................................................................................... 39

4.2.2 Slope Fragility of Watershed ....................................................................................................... 40

4.2.3 Forest cover Fragility .................................................................................................................. 42

4.2.4. Fragility using Population density .............................................................................................. 43

4.2.5 Proportion of Arable Land Affected by Erosion ......................................................................... 44

4.2.6 Average farm size fragility analysis ............................................................................................ 45

4.2.7 Total stability the sub basin ......................................................................................................... 46

4.3 Land Degradation and Soil Erosion ...................................................................................... 47

4.3.1 Water Erosion .............................................................................................................................. 50

4.3.2 Forms of Water Erosion .............................................................................................................. 50

4.4Soil Erosion Hazard Assessment Results ............................................................................... 56

4.4.1 RUSLE Parameters Results ......................................................................................................... 56

4.5Causes of Watershed degradation and Soil erosion ............................................................... 65

4.5.1 Population and Land Degradation Processes ............................................................................... 66

4.5.2 Deforestation and Overexploitation of Vegetation ...................................................................... 66


BoEPLAU Watershed Management Study DraftFinal Report ADSWE vi

4.5.3 Improper Agricultural Practice .................................................................................................... 67

4.6Effects of land degradation and soil erosion .......................................................................... 69

4.7Soil and water conservation Experiencesin the Sub Basin .................................................... 71

4.7.1 Indigenous Soil and Water conservation Structures .................................................................... 72

4.7.2 Physical Soil and Water Conservation Structures ....................................................................... 73

4.7.3 Biological Soil and Water Conservation ..................................................................................... 74

5. PROBLEM IDENTIFICATION .......................................................................................................... 77

5.1 Soil Erosion and Land Degradation ................................................................................. 77

5.2 Deforestation .................................................................................................................... 77

5.3 Decline of Soil Fertility .................................................................................................... 78

5.4 Weak Soil and Water Conservation Work and Management Practice .................................. 78

6. LAND MANAGEMENT PRACTICES/OPTIONS ............................................................................. 80

6.1 Capability Land Classification .............................................................................................. 80

6.1.1 Capability Inputs ......................................................................................................................... 80

6.1.2 Land Capability Classes .............................................................................................................. 82

6.2 Proposed Soil Water Conservation Measures .................................................................. 85

6.2.1 Physical Soil and Water Conservation Measures ........................................................................ 88

6.2.2 Biological Soil and Water Conservation Measures ..................................................................... 94

7. CONCLUSION AND RECOMMENDATION ................................................................................... 99

7.1 Conclusion ........................................................................................................................ 99

7.2 Recommendation ................................................................................................................... 99

8. REFERENCES ................................................................................................................................... 101

9. APPENDICES .................................................................................................................................... 103

Appendix I. RUSLE Estimation Parameter............................................................................... 103

Appendix II Secondary Data of Watershed Management ......................................................... 106


BoEPLAU Watershed Management Study DraftFinal Report ADSWE vii

LIST OF TABLES

Table 1: Climate (Rain fall) index based area classification (Nurhusen, 2006) ........................................... 14

Table 2: Slope Index Watershed Stability .................................................................................................... 14

Table 3: Erosion hazarded based fragility class assessment ......................................................................... 15

Table 4: Population fragility ......................................................................................................................... 16

Table 5: Soil color Erodibility Factor (Hellden, 1987) ................................................................................ 20

Table 6: P- value (Wischemeier and Smith, 1978) ....................................................................................... 22

Table 7: Tana Sub basin slope classification ................................................................................................ 28

Table 8: Major watersheds of Tana sub basin .............................................................................................. 38

Table 9: Tana Sub Basin Aridity index ........................................................................................................ 40

Table 10: Slope Index Watershed Stability .................................................................................................. 41

Table 11: Forest Cover as Criteria for Determining Catchment Stability Class .......................................... 42

Table 12: Arable land as a criteria factor for determining catchment stability class.................................... 44

Table 13: Average Farm as a Criteria Factor for Determining Catchment Stability Class .......................... 45

Table 14: Tana sub basin weighted overlay fragility analysis ...................................................................... 46

Table 15: Dry matter production from different land covers in the sub basin ............................................. 47

Table 16: Soil depth of the sub basin ........................................................................................................... 50

Table 17: Tana sub basin organic matter rating analysis .............................................................................. 51

Table 18: Tana Sub basin zonal Livestock population ................................................................................. 52

Table 19: Tana sub basin of sheet erosion observed data severity class ...................................................... 52

Table 20: Gully erosion amount by land cover at different depth ................................................................ 54

Table 21: Gully erosion by volume at different land cover .......................................................................... 54

Table 22: Tana sub basin stream bank erosion severity class ...................................................................... 54

Table 23: Mean Annual rain fall and R-values of Metrological Station of the Sub basin........................... 57

Table 24: Major watersheds soil loss rate in the sub basin .......................................................................... 63

Table 25: Tana Sub Basin Annual Soil Loss ................................................................................................ 64

Table 26: Demand and supply of the existing forest resource projection in the sub basin .......................... 66

Table 27: Total Achievement of SWC from2001-2005 EC with in the sub basin ....................................... 76

Table 28: Table Slope factor rating and proportional area coverage ............................................................ 81

Table 29: Soil depth rating and proportional area coverage ......................................................................... 81

Table 30: Soil erosion rating table ................................................................................................................ 81

Table 31: Soil drainage class of Tana sub basin ........................................................................................... 82

Table 32: Soil texture class distribution of study area .................................................................................. 82

Table 33: Land capability class and proportional area coverage in Tana sub basin ..................................... 83

Table 34: Proposed Soil and water conservation measures .......................................................................... 87

Table 35: The gradient, soil depth and width of a cultivated area (in meters) on a bench terrace. .............. 91

Table 36: Different sizes of gabions (Length x Width x Height) and wire requirement for each ................ 94

Table 37: Spacing for grass strip down a slope (RELMA and MOA, 2005) ............................................... 95

Table 38: FAO soil unit & their corresponding K values ........................................................................... 103

Table 39: Major soil unit, soil color and K- Values ................................................................................... 103

Table 40: K value based on the soil texture and organic matter content .................................................... 104

Table 41: Soil Erodibility Factor (K) (Schwab et al., 1981) ...................................................................... 104

Table 42: Crop Factor and land use land cover .......................................................................................... 104

Table 43: Land capability classes andSWC Options at different land cover ............................................. 104


BoEPLAU Watershed Management Study DraftFinal Report ADSWE viii

LIST OF FIGURES Figure 1: Biophysical Indicators for land degradation(Michael & Niamh, 2000) ....................................... 12

Figure 2: Values of the Gravelius's index for watersheds ............................................................................ 15

Figure 3: Map of Tana sub basin .................................................................................................................. 25

Figure 4: slope map of the sub basin ............................................................................................................ 28

Figure 5: Soil map of Tana sub basin ........................................................................................................... 30

Figure 6: Major land use land cover of the sub basin ................................................................................... 31

Figure 7: Flow diagram for soil loss estimation ........................................................................................... 34

Figure 8: Tana Sub basin major watersheds. ................................................................................................ 37

Figure 9:TanaSub Basin Rainfall Fragility ................................................................................................... 40

Figure 10:Tana Sub Basin Slope Fragility ................................................................................................... 41

Figure 11: Tana sub basin Forest fragility Map ........................................................................................... 42

Figure 12: Tana Sub Basin Population Fragility Map .................................................................................. 43

Figure 13: Arable land evaluation for classifying watershed stability ......................................................... 44

Figure 14: Average Farm Size Evaluation for Classifying Watershed Stability .......................................... 45

Figure 15: Tana Sub Basin Weighted overlay Fragility analysis ................................................................. 46

Figure 16: Sediment deposition near Lake Tana at Takusa and Gonder Zuria Woreda, ADSWE, 2014. .... 48

Figure 17: Soil depth of the sub basin .......................................................................................................... 49

Figure 18: Shallow Soil depth and Root over top of chemical degradation at Farata (right) and Dera

(left)ADSWE, 2014. ..................................................................................................................................... 49

Figure 19: Tana sub basin organic matter ratinganalysis ............................................................................. 51

Figure 20:Rill erosion South Achefer (left) and Dera (right) woredas ADSWE, 2014................................ 53

Figure 21: Gully erosion at Ebinat (left) and Farta (right) woredas, ADSWE, 2014. .................................. 53

Figure 22: Stream bank erosion Alefa woreda (left) and North Achefer woreda (right); ADSWE, 2014. .. 55

Figure 23: Roadside erosion Dembia (left), Farta (middle) and South Achefer (right) ADSWE, 2014. ..... 55

Figure 24:Tana Sub Basin Metrological Stations ......................................................................................... 56

Figure 25:TanaRainfall and Erosivity Map .................................................................................................. 58

Figure 26:Tana Sub Basin Soil and Erodiblity Map..................................................................................... 59

Figure 27: Tana Sub Basin DEM, Slope length, Slope gradient and LS Maps ............................................ 60

Figure 28:TanaSub Basin Crop factor Map .................................................................................................. 61

Figure 29:TanaSub basin Management Practice (P-value) map................................................................... 62

Figure 30: Soil loss map of the sub basin ..................................................................................................... 63

Figure 31: Tana sub basin average annual soil loss map .............................................................................. 64

Figure 32: Slope more than 30% are cultivated in the sub basin.................................................................. 68

Figure 33: Improper agricultural practice at Ebinat, West Belesa, Farta and Quarit ADSWE, 2014. ......... 69

Figure 34: Hydrological degradation Megech at Robit Dembia and Trikura river Takusa woreda, ADSWE,

2014. ............................................................................................................................................................. 70

Figure 35: Irrigation schemes Selamiko Dam (Debretabor), Drima weir at Dembia and Lake Tana (Gonder

Zuria and Fogera) woreda filled by Sediment load, 2014. ........................................................................... 71

Figure 36: Physical Soil and Water conservation at Farta, Mecha, Takusa and Fagita woreda, ADSWE,

2014 .............................................................................................................................................................. 74

Figure 37:Effective Biological Soil and water conservation Sekela and Fara ,ADSWE 2014. ................... 75

Figure 38: Poor SWC practice and management Gonder Zuria, Dera and Libokemkem ADSWE, 2014. .. 79

Figure 39: Land capability class map ........................................................................................................... 83

Figure 40: Proposed soil and water conservation measures ......................................................................... 87

Figure 41: Cross section of a bund ............................................................................................................... 89

Figure 42: Patterns of micro basins .............................................................................................................. 90


BoEPLAU Watershed Management Study DraftFinal Report ADSWE ix

ABBREVIATIONS AND ACRONYMS

ADSWE Amhara Design and Supervision Works Enterprise

CBPWD Community Based Participatory Watershed Development

DEM Digital Elevation Model

EMA Ethiopian Mapping Agency

ERDAS Earth Resource Data Analysis System

FAO Food Agriculture Organization

GIS Geographical Information System

GPS Global Positioning System

LADA Land degradation Assessment in Dry land Areas

Land Sat TM Land Satellite Thematic Mapper

LUPRD Land Use Planning and Regulatory Department

MoA Ministry of Agriculture

NGO None Governmental Organization

RUSLE Revised Universal Soil Loss Equation

SCRP Soil Conservation Research Project

SWAT Soil Water Assessment Tool

SWC Soil and Water Conservation

T/ha/yr Tons per hectare per year

UTM Universal Transverse Mercator


EPLAUB Watershed management Study Draft Final Report ADSWE 1

1. INTRODUCTION

1.1 Background

A watershed is any surface area from which runoff resulting from rainfall collected and drained

through a common confluence point. The term is synonymous with a drainage basin or catchment

area. Hydro logically, watershed defined as an area from which the runoff drains through a

particular point in the drainage system. A watershed made up of the natural resources in a basin,

especially water, soil, and vegetative factors. At the socioeconomic level a watershed includes

people, their farming system (including livestock) and interactions with land resources, coping

strategies, social and economic activities and cultural aspects.(CBPWD,2005). Now a day‟s

watershed degradation is a serious problem in the developing country like Ethiopia. Amhara

Region it is one of the region which affected by land degradation. Especially Tana Sub Basin is

one of the sub basin, which seriously affected by different land degradation.

Land degradation is the decline in land quality caused by human activities. The immediate causes

of land degradation are inappropriate land use that leads to degradation of soil, water and

vegetative cover.

Land degradation is the results of complex interactions between physical, chemical, biological,

socioeconomics and political issues of local, national, or global nature. Some of the causes of

degradation are natural hazards, population growth, expansion of agricultural lands on to forests

and marginal lands, poverty, land ownership problems, political instability and administration

problems, and inappropriate agricultural practice.

Land degradation manifests itself in many ways. Vegetation, which may provide fuel and fodder,

becomes increasingly scarce, watercourses dry up, thorny weeds predominate in once rich

pastures, footpaths disappear into gullies, and soils become thin and stony. All of these

manifestations have potentially severe impacts for land users and for people who rely for their

living on the products from a healthy landscape.

Types of land degradations are soil erosion by water, soil erosion by wind, soil fertility decline,

water logging, increase in salinity, flooding, lowering of water table, and loss of vegetation cover.

However, the sub basin affected with different types of land degradation such as physical,

chemical and biological degradation are the main problems in the study area.

The sub basin divided in to four major watersheds namely Megech, Rib, Gumara and Gilgel

Abay.



The sub basin has a total area of 1,579,096.94 hectares. The sub basin includes about 29 rural and

town woredas of the region. The sub-basin is one of the most important potential areas for all

developmental activities, especially for irrigation, livestock production, crop production, forest

production, tourism and mining. In addition, although it needs thorough study economically

important mineral resource found in this sub basin.

It has plenty surface and most importantly ground water resources, suitability to promote

commercial agriculture and agro-industry, access to market are to be mentioned as the good

opportunities of this sub basin. However, due to mismanagement or underutilization of land

resources the living standard of the farming community could not improve beyond subsistence.

Meanwhile the productivity of the land is seriously declining. This due to different watershed

management problems especially land degradation is the main mechanism for declining

productivity.

This watershed management study particularly deals with the existing natural resources inside the

watershed and future intervention for sustainabledevelop.

1.2 Scope of the Study

The watershed management study carried out at Tana sub basin in Amhara Regional State is

intended watershed management to degradation, utilization and conservation of natural resource.

The natural features of the watershed, topography, soil type, climate and socio economic

conditions, demography and farming system are study criteria to analyze the causes and effects of

soil erosion of the watershed. Conservation experience and benefits of soil and water

conservation studied .Major problems identified in the field of SWC and development measures

recommended with management and planning techniques. The study assessed land qualities and

characteristics related to land degradation for land evaluation process in land use planning

project. The land qualities quantified by fragility and soil erosion risk classes. Soil loss and

sediment yield estimations carried out. Soil loss equation is best indicator of land degradation.

The study based on overlay of soil geomorphology, climatic, present land cover possessed in Arc

GIS 10.1 environments.

1.3 Objectives of the Project

1.3.1 General Objective

The general objective of the watershed management study in the sub basin is in order to identify

and understand ecological and socio economic problems in the sub basin to identify and prepare



watershed intervention plan that enable sustainable management and use of resources: thereby

establishing sustainable production system to improve the livelihood of the communities in the

sub basin

1.3.2 Specific objectives

To study the existing soil erosion condition to indicate socio-economic and

ecological problems.

To study the soil and water conservation trend to understand the strength and

weakness of concerned bodies while transforming towards sustainable

development.

To estimate soil loss and potential sediment yield transporteddownstreamto Lake

Tanaby using RUSLE parameters.

To identify soil and water conservation measures overcoming the problem of soil

erosion

To study the condition of watersheds as a proper unit for wise utilization and

development of all land resources.

Recommend sound natural resource management strategy for sustainable

development to improve livelihoods and protecting ecosystem stability through

strengthening capacity for integrated land use planning and implementation.

1.4 Limitation of the study

Secondary data collection was not satisfactory process, because it was difficult to get documented

data of different seasons of soil and water conservation practices at woreda levels. Only data of

current year were available, data series in the recent past years not obtained.



2. LITERATURE REVIEW

2.1 History and Experience of Watershed Based Development

In Ethiopia, Different extension systems exercised for 54 years. However, the focus of extension

system has been on crop production and to some extent on livestock, no attention was given to

natural resource conservation and development. Watershed based natural resource management in

general and soil and water conservation in particular commenced in the 1980‟s though the

management was at large scale and top down. This has attributed largely to the unmanageable

size of the target areas and the lack of community participation and limited sense of

responsibility.

The watershed conservation was strictly soil erosion control and afforestation .It did not include

the socioeconomic transformation noticed in watershed development (Berhe, 1996).

The lessons learned from this experience encouraged MoA and support agencies like FAO to

initiate pilot watershed planning approaches on a bottom-up basis, using smaller units and

following community-based approaches. A number of participatory planning tools and

methodologies have been developed and tried out in Ethiopia. Recently, from several of these

approaches community-based participatory watershed development guideline extracted to provide

guidance to DAs and woreda experts on how to engage and consult with communities to prepare

a workable, socially acceptable, and technically sound community-based watershed plan.

Minimum planning at the initial stage involved shifting from larger watersheds to smaller sub-

watersheds. Community based sub-watershed approaches originated from watershed planning and

the minimum planning. The woreda level planning, which started in 1994, consisted of socio

economic survey and planning, biophysical indicators (land use land cover) and development plan

prepared for 3 years.

2.2 Experiencein Watershed Management in Amhara Region

Watershed management efforts in Amhara region have so far focused on the food insecure and

degraded areas. The food secure areas, which are eroding at increasing rate, had given little

attention. Existing efforts also focus on soil water conservation and water harvesting with heavy

emphasis on physical measures, rather than on broader program of watershed development.

Watershed development has been problematic when we applied without community participation

and using only hydrological planning units. This resulted in various failures or serious

shortcomings. For instance, large Borkena dam in South Wello, all irrigation dams constructed by



CoSAERAR and Angereb dam in North Gondar where constructed before not sufficient

conservation measures were in place. Similarly, about five large dams are going constructed in

Lake Tana watershed however; none of these will offer sustainable benefit in the current situation

of upstream degradation. Watershed management therefore, is important to the long–term

effectiveness of the sustainable utilization of the dams and Lake Tana reservoirs.

Thus, the national government has designed and launched a Community Based Participatory

Watershed Development approach to lead the process of rural transformation, the generation of

multiple and mutually reinforcing assets. Accordingly, Bureau of Agriculture and Rural

Development is being heavily involved in watershed management and declared that all resources

development projects should be watershed based.

In the past decades, participatory watershed development approach has taken on board by

different organizations including NGOs and bilateral organizations. GTZ has adopted

Participatory Land Use-Planning (PLUP) approach in implementation of soil and water

conservation and farming practices. South Gondar is one of zones were the organization has

succeeded in mainstreaming the participatory element into the land use-planning and natural

resources management approach.

The Amhara micro enterprise development, agricultural research, extension and watershed

management(AMAREW) project, since its beginning in July 2002,has been conducting multi-

faced and integrated rural development activities in targeted woredas of selected pilot watersheds

of the region in agricultural research, extension ,watershed management and micro enterprise

development. The organization has commenced operation in Sekota and Gubalafto since 2003.

Besides, the pilot in Sekela Woreda, which is part of Lake Tana watershed, has initiated since

august 2005. It gained experience in participatory watershed management on these pilot

watersheds.

These include participatory planning and implementation, demonstrating at small scale and

scaling up of activities. These all reach experiences of organizations working in the watershed

will be very helpful during implementation of the intended project.

2.3 Baseline Survey of Community-Based Integrated Natural Resources

Management Project in Lake Tana Sub-Basin, TCS (2013)

There are many community based integrated natural resources management study in Lake Tana

sub basin. Most of them focused on base line survey and on resource assessment only. For

example, baseline survey of community-based integrated natural resources management study



carried out by Temesgen Consultancy Service (TCS, 2013) focused mainly identifying the

existing types of soil and water conservation structures, analysing soil loss in Lake Tana sub

basin and estimating yield and associated economic loss only.

The amount of physical and biological conservation measures not well quantified in terms of

human and financial resources requirement. The study had no detail implementation plan and

time schedules. Besides, it did not specify the specific location for each conservation measures.

2.4 Baseline Information of Community-Based Integrated Natural Resources

Management Project in Lake Tana Sub-Basin, IFAD/EPLAUA (2007)

The study IFAD/EPLAUA (2007) indicated that land degradation in the Lake Tana watershed

limits the potential to develop a sustainable livelihood for its inhabitants. Deforestation,

sedimentation, and loss of fertility contribute to global warming, biodiversity loss, and restrict the

availability of fresh water while altering the structure and integrity of local ecosystems. Those

phenomena exacerbated by inappropriate land use and damaging agriculture and grazing

practices. The effectiveness of the regional and local efforts to improve the environment and

livelihoods of the residents in the Lake Tana watershed through natural resource conservation

programs are limited due to capacity, and financial barriers.

The study finally identified land use and water resource related barriers that include weak policy

implementation, low capacity (technical and financial), poor information management system,

low or no incentives, and frequent restructuring of core and principal institutions at

national/regional levels. Alleviation of these constraints will be important for better delivery of

technical support and enabling local users to implement good land use related practices, to

influence policies reduce dependency on aids and implement environmentally friendly activities.

The following alternatives are proposed by the study (IFAD/EPLAUA, 2007);

Strengthening capacity for integrated land use planning and implementation, at the

regional and local levels and across sectors

Development and Strengthening implementation of policies, regulations, and incentive

structures,

Strengthening and designing information management systems to support decision-

making at all levels on integrated land use planning and management.

Formulation of bylaws to govern wetland resource use as well as avert degradation of

wetlands as a result of mismanagement of streams and rivers feeding the wetland.



Creating awareness amongst communities on the useful functions of wetlands and the

sustainable utilization of land and water resources

Promoting integrated land-use planning with environmental conservation activities at

watershed, micro watershed level

Supporting and developing both extension staff and community capacity to

develop/introduce sustainable land use systems.

Improving the availability (quality and quantity) of potable water and irrigation water

through rainwater harvesting, diversion and spring development

Communication of Water Users along river resources at various spots is limited. Hence,

the water users‟ complaint from different users can be resolved by involving

representatives from different sites and setting equitable water use rights.

Besides, strategies adopted for removing the barriers to achieving Sustainable Land Management

(SLM) in Lake Tana Watershed are also stated.

However, thebaseline survey study lacked to draw detail implementable activities, where to

implement and the like; rather it gave a clue to commence a detail study. Hence, it is important to

undertake detail watershed management study to translate this study in to implementable project.

2.5 Megech-Seraba Pump Irrigation Project

This study (TAHAL, 2009) has no watershed management plan rather it conducted to undertake

soil suitability evaluations of the project area for irrigation of major crops. FAO guidelines for

land evaluation for irrigated agriculture, and USDA land classification system to assess the

capability of the project area. Land evaluation for surface irrigation based on matching the land

characteristics (slope range, drainage class, soil depth, soil texture, pH, EC, ESP, CEC, OM,

available P, infiltration rate, hydraulic conductivity and stoniness) of the command area and the

land use requirements for surface irrigation.

The results of the evaluation 4,323 ha from total command area were not suitable for surface

irrigation at that level of management due to drainage, flooding, shallow groundwater table and

heavy clay. The study recommend that , in order to run the irrigation project in a sustainable

manner, improvement of the slow drainage or water application that conforms to slow drainage,

flood control and groundwater rise is very imperative.

The study has relevance on land suitability classification aspects and discussed in detail for the

area, but it does not cover all the envisaged area and it is specific only the issue of irrigated area.

The study has to be considering for this study, however consideration of other LUTs is important.



2.6 Rib irrigation Project

The study undertaken by WWDSE/TAHAL (2008) on Rib irrigation project has recommended

Watershed Management Interventions such as: Physical soil and water conservation measures like

graded bunds and/or graded fanya-juu, level bunds, check dams, embankment or road cut slope,

cut-off drains, waterway construction and improvement and soil management; biological soil

conservation measures like grass strip and alley cropping, crop rotation and inter-cropping,

multiple cropping, intercropping, hedgerows, relay cropping, agroforestry and nursery

establishment and seedling production. in addition, area closure, river bank protection,

agricultural production enhancement, livestock management interventions, spring

development,alternative energy development, income diversification, infrastructure development,

agricultural production support systems, loan and credit, marketing, extension system

improvement, and participation of community and stake holders are other interventions

recommended for Rib watershed management. These recommended interventions complemented

with detail implementation schedule, quantity of work and budgeting. However, the study lacked

where and which recommended measures implemented. No spatial distribution of the measures

indicated except mentioning the requirement of recommended measures as slope, terrain

condition and the like.

2.7 Koga irrigation Project

The watershed management plan of Koga irrigation project feasibility (Acres and Shawel, 1995)

tries to describe about topography, slope, soil and land suitability, traditional agro-climatic zones,

land use and land cover types in the watershed area, review of the on-going watershed

management project, understanding of the watershed resources, and population of the watershed.

It, then, puts major problems of the Koga watershed; such as shortage of drinking water, soil

erosion, lack of irrigation facility, low crop yields as the major/dominant problems. The other

associated problems like unemployment, shortage of fuel wood, fodder etc. also needed to tackle.

Soil loss for the watershed also estimated on sub-watershed basis.

Watershed treatment planincluded soil and water conservation measures. Firstly, basic activities

like farmers training and preparation of seedlings in the nurseries. Secondly, arable land treatment

like conservation measures which consist of contour cultivation for all farmlands, diversion drain

about 20,000 meters, soil bunds 800km on 2000ha farm land, stone bund 100km for 1000ha and

fanya juu 100km for 500ha.In addition to these, production measures, which consist of crop

demonstration, agro-forestry, horticulture development, organic farming / compost pits,



homestead garden and household production system, planned implemented as watershed

management component of the project. About 400,000 USD also earmarked for the

implementation.

Hence, this study, unless some changes are expected, sufficient enough for implementation of the

watershed management plan every activities well mentioned. What it lacked is nothing but what

to do where.

2.8 Watershed Degradation

Depletion of water resources: Ethiopia suffers from what referred as a “recurrent wastage of most

of its rainwater”. With loss of water through surface runoff, soil eroded, thus triggering the whole

chain of negative consequences leading to chronic food insecurity. In most developing countries,

only 20–50% of total surface runoff is controlled and effectively used. Ethiopia is among them as

topography, inadequate farming practices, and lack of conservation hamper water and moisture

retention and its efficient use. Depletion of water resources directly linked to the disappearance of

vegetative cover and surface protection systems. High runoff also implies high erosion rates and

soil degradation, lower infiltration and a vicious cycle of depletion. Scarcity of water for domestic

and livestock use is a major consequence of degradation in Ethiopia, with serious repercussions

on health, incomes and the quality of life of people. Soil erosion and land degradation; Soil

erosion is one of the most important component of land degradation. Soil erosion and degradation

is a reduction in soil depth and fertility. It is caused by erosion (soil removal, loss of nutrients),

reduced soil water holding capacity and excessive exploitative use of the land (cultivation of

steep slopes, shallow soils, tillage, overgrazing, encroachment of forests/closed areas, and others).

If land and water resources not protected and conserved against the forces of erosion, soil

resources degradation occurs in various forms. In degraded watersheds, forms of degradations can

be physical, biological and chemical. Impoverishment of the vegetative cover is reduction of the

vegetative cover and biomass caused by climatic factors, over utilization of vegetation (such as

cutting of trees, overuse of crop residues for animal feed and fuel wood, overgrazing, and

burning), erosion and reduced soil fertility. If watersheds not managed properly then the natural

resources (soil, water, fauna - vegetation and flora) degraded rapidly and in due course not be

used for settlement of humans. The linkages among these three factors are obvious: land

degradation is mostly responsible for reduction of the vegetative cover and ultimately depletion of

the water resources that in turn makes the soil, water and vegetation more vulnerable to further

aggravation.



2.9 Land Degradation

Land degradation is a composite term; it has no single readily identifiable feature, but instead

describes how one or more of the land resources (soil, water, vegetation, rocks, air, climate,

relief) has changed for the worse. Land degradation generally signifies the temporary or

permanent decline in the productive capacity of the land (UN/FAO definition). Another definition

describes it as, “the aggregate diminution of the productive potential of the land, including its

major uses (rain-fed, arable, irrigated, rangeland, forest), its farming systems (e.g. smallholder

subsistence) and its value as an economic resource." This link between degradation (which often

caused by land use practices) and its effect on land use is central to nearly all published

definitions of land degradation. The emphasis on land, rather than soil, broadens the focus to

include natural resources, such as climate, water, landforms and vegetation. Other definitions

differentiate between reversible and irreversible land degradation. Whilst soil degradation

recognized as a major aspect of land degradation, other processes, which affect the productive

capacity of cropland, rangeland and forests, such as lowering of the water table and deforestation,

captured by the concept of land degradation.

Land degradation is, however, difficult to grasp in its totality. Therefore, we have to use

indicators of land degradation. Indicators are variables, which may show that land degradation

has taken place – they are not necessarily the actual degradation itself. The piling up of sediment

against a down slope barrier may be an 'indicator' that land degradation is occurring upslope.

Similarly, decline in yields of a crop may be an indicator that soil quality has changed, which in

turn may indicate that soil and land degradation are also occurring. The condition of the soil is

one of the best indicators of land degradation. The soil integrates a variety of important processes

involving vegetation growth, overland flow of water, infiltration, land use and management. Soil

degradation is, in itself, an indicator of land degradation. Farmers' concerns is a distinction is

made between productivity, which is defined as the inherent potential of a land system to produce

crop yields, and production, which is defined as the actual yield levels achieved by farmers. Land

degradation may reduce the inherent productivity of a system, but production levels may be

unaffected, or may increase as a result of compensating action being taken by the land user (for

example, the application of fertilizer). Land management practices may not exploit the full

potential productivity of the land. Land degradation, if defined as a loss in productivity, closely

aligned with the interests of farmers, whose major concern is the yield that they can achieve from

their lands. Although current harvest potential is critical to most farming decisions, farmers will

often take a long-term approach to land productivity. Farming activities can trigger or exacerbate



land degradation, storing up future problems for land users. Consequently, early identification of

risk-prone areas and management techniques is of interest to land users.

2.10 Land Degradation Indicators

Land degradation indicators are statistics or measures that relate to a condition, change of quality,

or change in state of land valued. They provide information and describe the state of the

phenomena, are useful to monitor changes and provide means to compare trends and progress

over time. The main challenge in identifying indicators is to select those that are sufficiently

representative and at the same time easy to understand and measure on a routine basis (LADA,

2002).Generally, land degradation indicators classified as quantitative and qualitative that

provides a simple and reliable basis for assessing change.

2.11Driving Forces, Pressure, State, Impact and Response Indicators

The driving forces, pressure, state, impact and response provide a convenient representation of

many of the factors related to land degradation. Indicators of drive forces include activities that

directly or indirectly cause land degradation (macro-economic policies, land use development,

population growth, poverty, land use and tenure condition, extreme climate events/ changes,

natural disasters, and water stress). Pressure Indicators are activities that may result in an

increased pressure on the natural resources (demand from agriculture and urban land use, nutrient

mining, demand for waste disposal, population growth, over-cultivation, over-grazing, and

demand for water uses). State Indicators reflect the conditions and status of degradation, as well

as the resilience to degradation (Land productivity decline, soil degradation and contamination,

soil erosion and salinization, loss of vegetation cover, loss of biodiversity). The effect and impact

of land degradation on natural resources, human well-being and society are the indicators grouped

under the impact indicators (land productivity decline, poverty and migration, land goods and

services, water cycle and quality, carbon storage decline, loss of biodiversity, changes in human

population size and distribution). Response indicators represent policies and actions taken

towards proper control of degradation (Macro-economic policies, land policies and policy

instrument, conservation and rehabilitation, monitoring and early warning systems, commitment

to international conventions, investments in land and water resources). Indicators of land

degradation can also group as biophysical and socio-economic FAO /LADA (2002).



2.11.1 BiophysicalLand Degradation Indicators

The root causes of land degradation are poverty and food insecurity combined with harsh climatic

variation, the immediate causes of land degradation are inappropriate land use (e.g., over-grazing,

excessive irrigation, extensive tillage and deforestation), degradation of soil, water and vegetation

cover and loss of both soil and vegetative biological diversity, affecting ecosystem structure and

functions. The biophysical impacts of land degradation, leading to loss of soil productivity,

include soil erosion by water and wind, salinization and alkalinisation and chemical, physical, and

biological degradation. Resulting soil degradation lowers the actual and/or potential capacity of

the soil to produce goods or services, while land degradation leads to a loss of intrinsic qualities

required for particular land uses. Biophysical indicators of land degradation are described with

respect to soil properties (soil fertility, soil productivity, compaction, and loss of topsoil and

subsoil), erosion (e.g., shifting sands over fertile soils, water turbidity and sedimentation, soil

loss, and gullying incidence), land cover/farming system & climate hazard (land cover change

and farming and grazing intensity, aridity, frost hazard), and land form (topography).

Figure 1: Biophysical Indicators for land degradation (Michael & Niamh, 2000)

2.11.2Socio-Economic Land Degradation Indicators

Socio-economic indicators refer to social and economic factors causing land degradation as well

as the impact of land degradation on economic & social setting. The root causes and at the same

time consequences, of land degradation are often, poverty and food insecurity combined with

extreme climatic variation such as drought, whether natural or anthropogenic. The options

available to poor farmers and land users (land managers) to improve their land are much more

constrained than the rich ones. Poor land managers/the land users are often forced to degrade land

for their day-to-day survival (to ensure food provision); have poor access to land, credit, cash,

labor, and livestock; and lack infrastructure, information and technology to improve agricultural



yields and face political marginalization to improve their lives. Due to poverty, the cause and

consequence of land degradation more pronounced among the poorest segments of the world‟s

population.Socio-economic indicators framed about key characteristics of poverty:Lack of

opportunity (lack of income, credit, land and other assets to attain necessities such as food,

clothing and shelter; insecurity (vulnerability to adverse shocks and limited means to cope); and

disempowerment (voicelessness and powerlessness to influence decisions).

Institutional factors: the main driving forces of land degradation are institutional and policy

distortions, failures in the public or government, private or market, civil or community sectors,

and civil strife. Lack of institutional support; apprehension to decentralize; inadequate

development of land and natural resources management policies; negative externalities of

privatization schemes; development of macro-economic policies that encourage land

mismanagement; and incomplete markets for environmental goods and services (e.g., that do not

internalize environmental costs) have decreased incentive and ability for collective action to

manage land and natural resources.

2.12Land Degradation Assessment

2.12.1Qualitative Land degradation Assessment

The main goal of classifying land based on stability indicator is to identify critical areas and

concentrate limited financial and work force resources onto the most seriously affected lands first.

Based on their stability watersheds classified into: (Fragile, Instable, Moderately stable and

Stable).This classification based on evaluation of biophysical and socio-economic indicators that

are easy to obtain and suitable to evaluate the stability of the catchment. All the indicators

evaluated by means of empirical "Stability coefficient" to describe the overall stability of a

particular watershed with regard to ecological stability and erosion hazard need for technical and

social improvements & food production.

2.12.1.1 Biophysical Indicators

Climate (R)

This parameter (climate) especially rain & temperature determines soil erodibility as well as

moisture availability to plant growth (biomass production). Generally, an area has classified arid

(fragile), semi-arid (instable), sub humid (moderately stable) and humid (stable) based on average

annual rainfall of the area.



Table 1: Climate (Rain fall) index based area classification (Nurhusen, 2006)

Rainfall

(mm/year)

Climate

Watershed stability

Class Coefficient

Below 400 Arid Fragile 0.1

400-800 Semi-arid Instable 0.4

800-1200 Sub humid Moderately stable 0.8

Over 1200 Humid Stable 1.25

Arid environments are extremely diverse in terms of their landforms, soils, fauna, flora, water

balances and human activities. Because of this diversity, no practical definition of arid

environments derived. However, the one binding element to all arid regions is aridity.

Aridity usually expressed as a function of rainfall and temperature. The hyper-arid zone (arid

index 0.03) comprises dry land areas without vegetation, with the exception of a few scattered

shrubs. True nomadic pastoralism frequently practiced. Annual rainfall is low, rarely exceeding

100 millimeters. The rains are infrequent and irregular, sometimes with no rain during long

periods of several years.

The arid zone (arid index 0.03-0.20) is characterized by pastoralism and no farming except with

irrigation. For the most part, the native vegetation is sparse, being comprised of annual and

perennial grasses and other herbaceous vegetation, and shrubs and small trees. There is high

rainfall variability, with annual amounts ranging between 100 and 400millimeters.

The semi-arid zone (arid index 0.20-0.50) can support rain-fed agriculture with more or less

sustained levels of production. Sedentary livestock production also occurs. Native vegetation

represented by a variety of species, such as grasses and grass-like plants, fortes and half-shrubs,

and shrubs and trees. Annual precipitation varies from 400-600 to 700-800 millimeters, with

summer rains, and from 200-250 to 450-500 millimeters with winter rains.

Arid conditions also found in the sub-humid zone (arid index 0.50-0.75). The term "arid zone"

used here to represent the hyper-arid, arid, semi-arid, and sub-humid zones.

Slope gradient (S)

This factor influences soil erodibility in that it controls surface run-off stability of catchment or

watershed classified as follows; catchment considered critical if more than 30% of its land area

has slopes steeper than 50% gradient.

Table 2: Slope Index Watershed Stability

Proportion of slopes (%)

Watershed stability

Class Coefficient

Over 30 Fragile 0.1

15-30 Instable 0.4

5-15 Moderately stable 0.8

0-5 Stable 1.25



2.12.1.2 Morphology and erosion rate of watershed (C)

Watershed classified as critical if the sediments from the steep headwater ranges not deposited on

adjacent flat land, but completely exported from the eco-system. Thus, the most stable watersheds

are the plain like watershed and the accumulation type watersheds. Highly instable types are

therefore those having narrow, steep valleys and short lengths with high relief energy. In terms of

stability, the U-profile type takes an intermediate.

The shape of a catchment affects the stream flow hydrograph and peak flow rates. Shape of

watersheds varies considerably usually influenced by the geological processes. Commonly, the

slope resembles a leaf shape, the drains resembling the midrib and veins. Watershed shapes

described according to their physical configurations such as square, rectangular or oval shape.

However, indexes, approximates best the shape of a watershed.

The most frequently used index is the Gravelius's index KG, which defined as the relation

between the perimeter of the watershed and that of a circle having a surface equal to that of a

watershed.

Where: KG= Gravelius's shape index: A= watershed area [km2], P= watershed perimeter [km]

rank. Shape of watershed/catchment identified either in the field or in the office by means of

assessing shape factor in Arc hydro tools in GIS environment for each micro watershed.

Figure 2: Values of the Gravelius's index for watersheds

Table 3: Erosion hazarded based fragility class assessment

Erosion hazard

Watershed stability

class Coefficient

High Fragile 0.1

Medium Instable 0.4

Moderate Moderately stable 0.8

Low stable 1.25



2.12.1.3Socio-Economic Indicators

With regard to human involvement in the land degradation process, it is not necessary for a

society advanced agriculturally to do long-term damage to the land resources. Though human

causes, in the form of either mismanagement or deliberate damage, have contributed toward land

degradation, sometimes nature itself is the driving force.

Long-term changes in rainfall or general climate as well as soil erosion can turn an area into

permanently unproductive. An ecosystem may survive short-term drought, but if soil forced to go

too long without proper moisture, it sets in motion a chain reaction in which plant life dwindles

and, with it, animal life as well. Thus, the soil denied the fresh organic material necessary to its

continued sustenance, and a slow, steady process of decline begins.

Through social and economic occurrence an area of land may be defined as critical if: More than

about one third of all agricultural (arable) fields are affected by severe rill and/or gully erosion or

show signs of sheet erosion (exposed stones and / or roots). The average farm household produces

less than about 2.0 quintals of cereals per head per year, the average farm size is below one ha

and population density exceeds 50-75 persons per km2.

Table 4: Population fragility

2.12.2 Quantitative Land degradation assessment

2.12.2.1 Soil erosion hazard assessment

The assessment of erosion hazard considered as a special form of land resource evaluation to

identify those areas of land where the maximum sustained productivity from a given land

threatened by excessive soil loss. The land evaluation domain broadened from land suitability to

land vulnerability. Land vulnerability (referred to soil erosion, soil salinity, soil contamination,

subsoil compaction etc.) focuses on environmental degradation assessment (Deore, 2005).

Soil is a renewable resource so long as its use balanced with the soil formation rate. However, in

the watershed extensive land degradation has occurred because of deforestation, overgrazing and

inappropriate agricultural practices. This has resulted in both soil erosion and loss of fertility of

highland areas of the watershed where half of the arable land eroded. Sheet and Rill erosions are

the most prominent features to almost all cultivated lands of this watershed. Degradation of soil

Population Density (Persons/ Km2) Watershed stability

class Coefficient

>75 Fragile 0.1

50-75 Instable 0.4

25-50 Moderately stable 0.8

<25 stable 1.25



and vegetation resources leads to increased vulnerability to environmental shocks, decreased

agricultural production, reduction in access to basic services (water and electricity), demographic

instability, loss of carbon reserves, and loss of ecosystem resilience.

The population pressure, which is alarmingly increased, contributes a great share in expanding

cultivation of marginal lands. Increasing human and livestock population on one hand, and

diminishing of the existing arable lands on the other hand could help to increase the proportion of

degraded lands. This problem is more aggravated on the highlands of the watershed where 88%

human and 70% of animal population live (Kruger et al, 1996).

The annual soil loss in Ethiopia is between 1.5 and 3 billion tones (EHRS, 1986). From this about

50 percent occurs in croplands where soil loss has been reported to be very high (296

ton/ha/year). The Ethiopian Highlands Reclamation Study (EHRS) study estimated that about 50

percent of the highlands already significantly eroded.

Constable (1985) indicated that about 50% of the highlands already eroded, and cautioned that if

present soil degradation trends continue, per capita income in the highlands reduced on average

by 30% in the year 2010. though there is no a single research conducted in the watershed, Plot

experiment of Soil Conservation Research project (SCRP) at Anjeni (West Gojam) adjacent to the

watershed on different slopes and conservation practices showed soil loss between 53 and 161 t/

ha/year. Similarly, 152 t/ha was estimated in Angereb Watershed (Admasu, 2006).

Out of the total soil loss in the country (1.9 billion tone) about 1.1 (58%) is estimated to be from

the Amhara Regional State though the region covers only 16.7% of the total area of the country

(Gizachew, 1991). This shows significant portion of the region affected by soil erosion.

According to Berhanu (2003), about 29% of the region categorized under high erosion hazard. As

a result, 51 to 200 tons of soil eroded from each hectare of land every year. Nearly 37% of the

region identified as not suitable for crop production due to limiting soil depth (Teshome, 1995).

Consequent to the soil erosion the productivity of the soil reported to decline at a range of 2 to 3%

per year in the Amhara region

The estimated soil erosion rates of Lake Tana watershed is about 230 t/ha. This must have

increased at least by considerable percent from the present trends of soil erosion, accompanied

with complete absence of integrated watershed management.

2.12.2.2 Soil Loss Estimation Models

The researchers reported that much of the reduced yield observed on eroded soils was due to a

decrease for water available to the plant on eroded soils. On some soils, these crop yield



decreases largely overcome by higher fertilization levels. On other soils, particularly more

shallow soils on sloping terrain, erosion may destroy productivity if appropriate conservation

practices not initiated.

Soil losses, or relative erosion rates for different management systems, estimated to assist farmers

and government agencies in evaluation of existing farming systems or in planning to decrease soil

losses. In now, a day‟s method of estimating losses based on statistical analyses of field plot data

from small plots was developed, which resulted in the Universal Soil Loss Equation (USLE).

The soil loss affected by slope steepness and slope length, climatic characteristic, soil

characteristics, crop management and conservation practices, these factors considered for soil loss

estimation. In this regard, the effect of climatic factor in terms of rainfall erosivity index and crop

management factor taking into account effectiveness of different growth stages of the crop on soil

loss introduced. Similarly, the effects of conservation practices and soil erodibility on soil loss

also evaluated later on. Ultimately, by considering all these factors, a predictive equation

developed for estimating the soil-loss called as universal soil-loss equation.

The USLE continues to be a widely accepted method of estimation soil loss despite its

simplification of the many variables involved. It is useful for determining the adequacy of

conservation measures in farm planning, and for predicting nonpoint sediment losses in pollution

control programs. The average annual soil loss, as determined by Wischmeier and Smith (1978),

estimated from the equation.

Universal Soil Loss Equation: the equation given by:

PCSLKRA .....

Where, A = average annual soil loss in ton/ha,

R = rainfall factor (erosivity index) from rainfall map of the area; K = Soil erodibility factor; L =

slope length factor; S = Slope steepness factor; C = cover management factor; P = conservation

practice factor (terracing, Strip-cropping and contouring).

By application of this equation, the average annual soil loss computed for any region; but before

using it, its validity verified. The different factors associated with this equation described below.

Rainfall Factor (R): refers to the rainfall and runoff erosivity index, which expresses the ability of

rainfall to erode the soil particles from an unprotected field. The soil loss closely related to

rainfall partly through the detachment power of raindrop striking the soil surface and partly

through the contribution of rain to runoff (Morgan, 1994). This applies particularly to erosion by

overland flow and rills for which intensity generally considered the most important rainfall

characteristics. There are different ways of analyzing the R factor.



R = 9.28 * P – 8838. Mean annual erosivity (KE > 25) where P is mean annual Precipitation

[Morgan (1974) cited in Morgan (1994)],

R = 0.276 * P * I30. Mean annual EI30, where P is mean annual precipitation [Foster et.al (1981)

cited in Morgan (1994)],

R = 0.5 * P (in US unit) and R = 0.5 * P *1.73 (in Metric unit). [Roose (1975) cited in Morgan

(1994)].

The above formulas applied in different parts of the world. The first equation appears to work

well for Peninsular Malaysia, whereas the application for other countries is less satisfactory.

Especially with the annual rainfall below 900mm, the equation yields estimates of erosivity,

which are obviously meaningless (Morgan, 1994). In line with this, the second equation needs the

value of I30 for calculating of erosivity factor, which is difficult to get in context of the study area.

However, rainfall kinetic energy and intensity data are not available most cases. Therefore, the

erosivity factor calculated according to the equation given by Hurni (1985), derived from a spatial

regression analysis (Hellden, 1987) for Ethiopian conditions based on the easily available mean

annual rainfall (P).

R = -8.12+0.562*P; Where, P is the mean annual rainfall, mm

Soil Erodibility Factor (K). Physical characteristics of the soil greatly influence the rate at which

different soils eroded. Some more important soil properties such as the soil permeability,

infiltration rate, soil texture, size & stability of soil structure, organic content and soil depth, also

affect the soil loss in large extent. The soil erodibility factor (K), expressed as tones of soil loss

per hectare per unit rainfall (erosivity) index from a field of 9 percent slope and 22 meters as field

length. The erodibility factor (K) is determined by considering the soil loss from continuous

cultivated fallow land without the influence of crop cover or management. A nomograph to

estimate K for a given soil on which it not known presented or calculated from the regression

equation:

)3(103.3)2(103.4)12(108.2 3314.17 cbaMK.

Where M = Particle size parameter (%silt + %very fine sand) x (100-% clay), a = Percent organic

matter, b = soil structure code (very fine granular, 1; fine granular, 2; medium or coarse granular,

3; blocky, platy, or massive, 4), c = Profile permeability class (rapid, 1; moderate to rapid,2;

moderate,3;slow to moderate, 4;slow, 5; very slow, 6).

The value of K ranges from 0 to 1. Hellden (1987) developed a USLE for Ethiopian condition by

adapting different sources and proposed the K values of the soil based on their color. Factor data



for the Soil Conservation Research Project (SCRP) and are have prepared Ethiopia reproduced

(SCRP, 1996b).

Table 5: Soil color Erodibility Factor (Hellden, 1987)

Soil color Black Brown Red Yellow

K factor 0.15 0.2 0.25 0.3

The value of factor (K) also prepared by FAO 1989 in its Reconnaissance Physical Land

Evaluation in Ethiopia from the soil database relating the FAO soil unit classes and K value.

Since the soil data of the study area are in their geomorphological name, an attempt were made to

classify the soil types of the study area based on their color by referring the FAO soil database.

The soil map of the study area collected at a scale of 1: 1,000 000 from FAO soil map of East

Africa since 1997.The K values adopted from the study of Abbay River Basin Integrated

Development Master Plan Project, Ministry of Water Resources (MoWR) which studied by

BCEOM (1998). Influencing factors of soil erodibility are soil characteristics such as

permeability, infiltration, water-holding capacity, distribution of particles, aggregate stability,

tendency towards dispersion and absorption, transportability, structure, and humus content.

Slope Length and Steepness Factor (LS): Topographic factor defined as the ratio of soil loss from

a field having specific steepness and length of slope (i.e. 9 percent slope and length 22m) to the

soil loss from a continuous fallow land. The topographic factors (L, S) are given by L = (λ /

22.12) m

. where λ is the projected horizontal distance in meters between the onset of runoff and

the point where runoff enters a channel larger than a rill or deposition occurs. In addition, S =

65.4 sin2 θ + 4.56 sin q + 0.0654, where θ is the angle to horizontal, in the USLE but S = 10.0 sin

θ+ 0.03 slopes <9%& S = 16.8 sin θ - 0.50 slopes ≥ 9% in the RUSLE. In the USLE, m varies

from 0.6 for slopes > 10 % to 0.2 for slopes < 1 %.In modeling erosion in GIS, it is common to

calculate the LS combination using a formula:

LS = (Flow Accumulation * Cell Size/22.13)^0.4 * (sin slope/0.0896)^1.3 where Flow

Accumulation is the number of cells contributing to flow into a given cell and Cell Size is the size

of the cells being used in the grid based representation of the landscape. This formula based on

the suggestion by Moore and Burch (1986a, b) that there was a physical basis to the USLE L and

S factor combination. Moore and Wilson (1992) observed that the product of L and S in the

RUSLE could be approximated by LS = (As/ 22.13) 0.6 (sin θ / 0.0896) 1.3, whereas is the

upslope contributing area divided by the width of the contour that that area contributes. The

equation considers m = 0.6 and n = 1.3. For erosion at a point, Griffin et al. (1988) modified and

recommended the following formula. Where X = slope length (m) and S = slope gradient (%),

X = (Flow accumulation * Cell value), by substituting X value, LS equation will be:



LS = (Flow accumulation * Cell value /22.1) 0.6

(sin (S)*0.01745 / 0.09)1.3

LS = (X/22.1)0.6

(sin(S) *0.01745/0.09)1.3

The values of X and S will be derived from DEM. Contours at 20 m intervals were digitized from

a1: 50 000 scale topographic map and from this contour TIN is created and converted to DEM

(Raster) with 100m output cell size. To calculate the X value, Flow Accumulation derived from

the DEM after conducting FILL and Flow Direction processes in Arc GIS 9.By building an

expression in the Raster Calculator:

The slope length and gradient factors estimated from Digital Elevation Model data in the GIS

environment. The technique described here for computing LS requires a flow accumulation grid

layer and slope grid layer. The flow accumulation computed from hydro logically corrected DEM

(Digital Elevation Model). Flow accumulation grid represents number of grid cells that are

contributing for the downward flow. The cell size of the DEM represents the length of the cell.

LS = (Flow Accumulation*Cell size/22.13)0.4

*(Sin slope/0.896)1.3

Where: - Cell size- represents the field slope length;22.13 is the length of the research field

plot where the equation derived.

Land cover factor (C): the Land Cover factor represents the ratio of soil loss under a given land

cover to that of the base soil (Morgan, 1994). As Nyssen, (1997) commented, the land cover

factor „C‟, is of paramount importance in the determination of erosion hazard assessment because

of the large difference between its minimum and maximum values therefore slight mistakes in

land cover mapping can result in large over or under estimations of soil loss. For this reason, up-

to-date and accurate land cover map used for analyzing the c-value. After changing the classified

vector data to grid, a corresponding C-value assigned to each land use classes using reclassify

method in Arc GIS 9.3.

Conservation Practices Factor (P): It may be defined as the ratio of soil loss for a given

conservation practice to the soil loss, obtained from up and down the slope. The conservation

practice consists of mainly contouring, terracing and strip cropping, in which contouring appears

to be most effective practice on medium slope ranging from 2 to 7 percent. The soil loss from

contouring ranges about one-half of the total soil loss that occurs from up and down hill farming

system. In general, as land slope decreases from medium to zero, the effectiveness of contour

tillage to reduce soil loss decreases, compared to the non-contoured tillage field. Similarly, when

land slope increases from medium to steep slope, the contour row diminishes its capacity to

reduce the soil erosion or loss, because of having a very little capacity to detain the water on soil.



In strip cropping, the meadow strips alternate with grain strips tend to slow down the surface flow

and thereby catching of eroded soil from cultivated strips achieved. Similarly, the terraces in hilly

areas intercept the surface flow down the slope before attaining to an erosive velocity to damage

to land. From filed observations, found that when strip cropping adopted with the terracing

practice, then it becomes more effective to control erosion and soil loss.

The conservation practice P found from the equation

tsc PPPP

Where Pc = contouring factor based on slope;

Ps = strip cropping factor for crop strip widths recommended (1.0 for contouring only or for

alternating strips of corn and small grain, 0.75 for 4-year rotation with 2 years of row crop, and

0.50 with 1 year of row crop);

Pt = terrace sedimentation factor (1.0 for no terraces, 0.2 for terraces with graded channel sod

outlets, and 0.1 for terraces with underground outlets).The Pt factor will predict the amount of

sediment actually delivered from a given terrace. It is possible to predict either sediment detached

from the cropping area, and not include the terrace factor, or sediment leaving the field, and

include the terrace factor.

The erosion management practice, P value, is also one factor that governs the soil erosion rate.

The P-value ranges from 0-1 depending on the soil management activities employed in the

specific plot of land. These management activities are highly depends on the slope of the area.

Wischmeier and Smith (1978) calculated the P-value by delineating the land in to two major land

uses, agricultural land and other land. The agricultural land sub-divided in to six classes based on

the slope percent to assign different P-value.

Table 6: P- value (Wischemeier and Smith, 1978)

Land use type Slope % P-factor

Agricultural land

0-5 0.1

5-10 0.12

10-20 0.14

20-30 0.19

30-50 0.25

50-100 0.33

Other All 1.00

2.12.2.3Soil Loss Tolerance (T)

Since erosion is a natural process not prevented, but it reduced to an acceptable rate (Morgan,

1986). The maximum acceptable rate of soil erosion is the soil loss tolerance (Morgan, 1995).

The only tolerable rate of soil loss equals the rate of soil formation. However, although the rates

of soil loss measured, the rates of soil formation are so slow that they cannot be easily



determined. The rate of soil formation throughout the world estimated to range from 0.001 to 7.7

mm/y (Buol et al., 1973) and the average is about 0.1mm/y (Zachar, 1982). In Ethiopia, Hurni

(1983 quoted by Nyssen,2003),categorized average soil formation rates based on the agro-

climatic zones which are delimited based on altitude(m) and annual rainfall(mm).Accordingly the

soil formation rates ranged from 1tone/ha/year for Bereha „desert‟(altitude,500m)to 16

tone/ha/year for Wet Woina Dega (altitude:1500-2300m;annual rainfall.1400mm) agro-climatic

zones.

Due to a wide variability of conditions affecting the rate of soil formation in a given locality,

current values for soil loss tolerance are uncertain. Morgan (1995) also indicated that a better

guideline to estimate tolerable soil loss an assessment of the rate of natural soil loss in the

area.Soils with shallow root zone or other restricting characteristics generally assigned lower

tolerances (Kirkby and Morgan, 1980 quoted by Smith et al., 1997).Deep, medium textured,

moderately permeable soils with subsoil characteristics favorable for plant growth assigned

tolerances of up to 11 tone/ha/yr (Smith et al., 1997) soil loss tolerances of 3 to 10 tone/ha/yr

therefore considered for practical purposes.

The objective of conservation planning is to control average annual soil loss to a particular level,

which is usually soil loss tolerance (T). Shallow and fragile soils that not be easily reclaimed after

serious erosion are assigned low tolerance values. Limiting soil loss to tolerance controls erosion

so that soil protected as a natural resource and its productive capacity maintained for an extended

period. Soil loss tolerance considers the damages caused by erosion and the benefits of soil

conservation.

Soil loss values principally developed for cropland soils, Tolerance values also used for

conservation planning for reclaimed surface mines, landfills and military training sites.

Controlling erosion greatly facilitates establishing vegetation. For example, applied mulch cover

controls erosion and promotes seed germination and early growth of vegetation. In addition,

erosion control regulations for reclaimed land require that excessive rilling prevented. A rule of

thumb is that rilling begins when soil loss exceeds about 7 tons per acre (15 tons per hectare) per

year, which is met by tolerance values less than 5 tons per acre (11 t/ha) per year.

Soil tolerance values are primarily for protecting the soil as a natural resource and not for

protecting offsite resources from excessive sedimentation or water quality degradation. The

criteria for controlling sediment yield from a site based on how both amount and sediment

characteristics affect the resource. The usual approach for using soil loss tolerance in



conservation planning is to assume a uniform slope having a slope from the origin of overland

flow to either where deposition occurs.



3. MATERIALS AND METHODS

3.1 Description of the Study Area

Tana sub basin found in the Amhara region. Geographically, the basin is located between North

latitude 1210669m – 1411084m and East longitude 254549 - 416363m. Its elevation is ranging

1327 - 4109 meter above sea level. The basin has a total area of 1,579,096.94 hectares. It is one of

the most important potential areas for all development in Amhara region. The largest lake in

Ethiopia, Lake Tana found in the sub basin.

Parts or the whole of 29 Woredas and 4 administrative zones are encompasses in the sub-basin.

These include Banja, Fageta Lekuma and Dangila Woredas in Awi zone. Sekela, South Achefer,

North Achefer, Mecha and Bahir Dar Zuria Woredas in West Gojjam zone. BahirDar Town in

BahirDar Liyu zone; Dera, Estie, Farta, Libo Kemkem, Ebinat and Fogera Woredas in South

Gondar zone; Debre Tabor Town in Debre Tabor Town Administration; Gondar Zuria, Wogera,

Lay Armachiho, Dembia, Chilga, Alefa and Takusa in North Gondar zone and Gondar Town in

Gondar Town Administration

Figure 3: Map of Tana sub basin



Human population in Tana Sub Basin is generally homogeneous linguistically and consists of the

main ethnic families of Amhara. According to CSAs 2007 census and Woredas, the study area

has a total population of 3,158,247 with male 1,587,394and female 1,570,853 this is about 16

percent of the total regional population. The very big proportion or 76.9 percent of the population

of the area is living in rural areas where as the remaining 23.1 percent are concentrated in urban

and semi urban centers. The settlement pattern of the study area is dominantly scattered and the

average population density of the area is 200 persons per km square.

The sub basin is endowed with eight different agro-climatic zones namely, moist tepid, sub-

humid tepid, moist cool, moist warm, moist cold, moist very cold, sub-humid cool and sub-humid

cold. Most of the project area (79.4%) is found in moist tepid agro climatic zone followed by sub-

humid tepid, moist cool and sub-humid cool which account for 12%, 5% and 3% respectively.

The area dominated by one main rainy season, from June to September and one dry season

between October and May. The rainfall distribution of area is controlled by the northward and

southward movement of the inter-tropical convergence zone (ITCZ) resulting in a single rainy

season.

Physiographically, Tana sub basin is categorized under four major watersheds, namely Megech,

Rib, Gumara and Gilgel Abay. The sub basin is diverse topographic feature ranges from lowland

plain, mountainous and raged topography cover. The large plain areas around Lake Tana are often

flooded during the rainy season, such as the Shesher and Welela plain in the east, the Dembia

plain in the north, the Kunzila plain in the west, and marshlands at the peripheries of the whole

lake. The mountainous terrain and raged topography (Guna Mountain, Parts of Sekela, Wegera,

Lay Armhachoiew, Libokemkem, Gonder zuria West Belesa ,Ebinat, Farta and Quriet).

River Megech, Rib, Gumara and Gilgel Abbay are the main permanent water resources in the

Basin, However, the Megech and Rib rivers sometimes dries-up at downstream during the dry

seasons. Both Rivers used to supply water for human and livestock consumption and for crop

irrigation. The others seasonal rivers originate from the upper in the mountainous range in the

north and in hilly zones in the inter-riverine area of river Megech and Rib are also other sources

of water. RiverInfranz, River Jema, River Awra Arda, River Derba, River Arno-Garno, River

Shine, River Selamko, River Dengura are some of prominent seasonal rivers found in the study

area.

The sub basin is one among the other agrarian areas of the nation, where by Agricultural field

crop production is predominantly prevailing. With this respect, Agriculture production is the

mainstay for the livelihood of people in the sub basin. Beyond the presence of huge arable land



resource, the sub basin adequately endowed with a wide variety of indigenous plants with a

unique heritage of diverse germplasm of vegetables, fruits, oil crops, forages, tubers, cereals and

pulses. Teff, Noug, safflower, rapeseed, caster bean, Gesho, are among indigenous plants grown

in the basin. Maize, sorghum, beans, barley finger millet, wheat, chickpea and others are

commonly grown crops.

Livestock constitutes a major part of the farming system next to crop production, providing draft

power, producing milk and conferring a certain degree of security against crop failures. However,

performance in the production of the major food commodities of livestock origin has been poor

compared with other African countries, including neighboring Kenya (IFAD/EPLAUA, 2007).

Inadequate feed and nutrition, widespread diseases and poor health, poor breeding stock, and

infrastructure as major constraints affecting livestock performance.

Forest resource offer the main energy supply is one of the most dynamic economic activity in sub

basin; it also contribute to sustainable agricultural systems; and are a source for agro-biodiversity

and a major storehouse for carbon and water. However, Forest resource in the sub basin depleted,

biodiversity is declining, timber and non-timber forest products and services weakened, and most

of the important biological endemic species, that have a potential to sustain the livelihood in the

basin, are now vulnerable.

The sub basin is rich in fish and wetland resources. However, the fishery of Lake Tana is at an

early stage of development due to low level of technology employed by fishery man and a lack of

marketing facilities. On other hand the wetlands resources also declining due to ever-increasing

populationin the study area coupled with inappropriate land use and wetland management system.

The position of the basin in its cultural heritage is remarkable. For example, Some 37 islands &

21 monasteries surviving remnants of a very old meditative tradition have been used as safe

keeping places for the religious relics and art treasures during the times of trouble. In addition,

these monasteries from all corners of the country have architectural significances, beautiful mural

paintings and icons, as well as numerous strikingly illustrated parchments and intricately

decorated processional and hand crosses. It is also house myriads of treasures, beautiful mural

paintings, icons, parchment manuscripts, scrolls and emperors assets. However, efforts and

progress made on archaeological searches for historical values in the area are still at infancy. As a

result, most of the attractions including those that have been declared world heritage by UNESCO

have long suffered from severe deterioration by both natural calamities and human interferences



3.1.1 Slope

The slope class generated from DEM indicates that the sub basin has slope classes ranging from

0 to 60% and above.

Figure 4: slope map of the sub basin

Table 7: Tana Sub basin slope classification

The sub basin is classified into seven slope classes and the dominant slope classes are flat and

gently sloping land form covers about 556340.3 ha (35.23%) and 302457.34 ha (19.15%)

respectively from total coverage the rest are indicated in table7.

Slope Range Land form Area_ha Coverage (%)

0-2% Flat 556340.3 35.23

2-5% Gently sloping 302457.34 19.15

5-8% Sloping 153841.57 9.74

8-15% Rolling 239789.31 15.19

15-30% Moderately steep 223945.8 14.18

30-60% Steep 97608.65 6.18

>60% Very steep 5113.96 0.32

Total 1579096.94 100.00



3.1.2Soil condition in the sub basin

As there is strong relation between landform and soil characteristics, samples to characterize soil

type taken as per the major landform types within the watershed. Because of similarity in

landforms, the soil characteristics are almost similar for most of the mapping units.

a) Soil color: soil color is useful indicator of drainage.

b) Soil texture: soil texture is mainly concerned with size and shape of mineral particles.

Soil erosion depends much on the infiltration rate of the soil. The infiltration rate again

depends on soil texture. Hence, the decision for selecting graded or level physical soil

conservation structures on cultivated lands mainly dependent on soil texture. For example,

for clayey soil graded structures recommended because of less infiltration rate. The

textures identified with in the sub basin are clayey, silt and sand with their textural classes.

c) Soil depth: It refers the depth of the soil above a layer of hard rocks, stones or other

materials, which hinder root penetration. In this basin soil depth classes from shallow to

very deep with small proportion of shallow soil at the periphery of the basin.

According to the soil survey study of the sub basin, the total area covered with 12 major soils.

These are Acrisols, Alisols, Ferralsols, Gleysols lixisols Cambisols, Fluvisols, Leptosols,

Luvisols, Nistosols Vertisols and Regosols. From the twelve major soils identified Vertisols,

Luvisols and Nistosols are the dominant soils in the study area.



Figure 5: Soil map of Tana sub basin

3.1.3 Land Use/ Cover

The major land cover with in the sub basin are cultivated, forest, shrubs, grassland, water body,

wet land and built up area in different proportions.



Figure 6: Major land use land cover of the sub basin

3.2 Materials and Equipment

The watershed management study of the Tana Sub-Basin conducted under the Amhara Design &

Supervision Works Enterprise, Land Use Planning and Environmental Studies Work Process,

Tana Sub-Basin Land Use Planning Project, utilized different materials. These materials collected

from different offices Ethiopian mapping agency (EMA), Amhara Design & Supervision Works

Enterprise and Amhara Region.

The following materials used for the study:

Computer facility with GIS and Remote sensing programs;

Field data collection format prepared for the study;

GPS with Alkaline battery;



Tape meter

Digital data like administrative maps, satellite imagery, FAO digital soil map,

ASTER_DEM data.

3.3 Methodology

The methodology employed includes collection of primary and secondary data at field

level. The primary data collected in the field by using checklists of biophysical land resources

survey based on the prepared land cover, slope class and by asking key informants. The

secondary data collected from development agents and woreda expert by using readily made

questionnaires and by making discussion with the concerned experts. Soil erosion by water

estimated using RUSLE model. The study approaches and procedures exercised during different

stages of the study include pre-field work, fieldwork, and post fieldwork activities.

3.3.1 Pre Field

Base Map Preparation

During pre-field work, the main activities were concentrated on base map preparation. To make

the land resources survey activity simple and economical the Digital elevation Model (DEM) and

satellite imagery (Land Sat and Spot_2.5) of the project area were collected and land use / land

cover, shape file were developed. In addition to the Land use / cover base map, the watershed

boundaries, drainage lines and their networks and slope of each watershed extracted from 90m

DEM data by using Arc-Hydro tool extension in the ArcGIS environment.

Guideline development/Preparation

The general guideline for detailed land use planning project was prepared.

Preparation of check lists and questionnaires for:

Field data collection format prepared for biophysical survey.

Secondary data format was prepared.

The observation point selected based on the prepared base map at different slope class.

3.3.2 At Field

The following activities were undertaking; the sub basin fully covered during the study. Hence,

the primary and secondary data of the study collected.

Primary Data Collection

The study conducted mainly by primary data collection. Field observation of selected sites and

transects along selected routes with the aid of GPS and maps to investigate different biophysical



data, land form, land cover and forms of soil erosion, soil depth and stoniness, flood marks and

conservation practices. Inaddition, qualitativedescription made.

Secondary Data Collection

The secondary data collected from woreda and regional experts by using readily made

questionnaires and by making discussion with the concerned experts.

3.3.3 Post Field

3.3.3.1 Data Analysis and Interpretation

Watershed Delineation

By using Arc GIS and Arc Hydro, Arc SWAT software extensions further watershed delineation

done for large watersheds based on community based participatory watershed principles and the

final name and number of watersheds identified

Land degradation actually is a land quality considered in land use planning as it influences the

utilization of the land; it is the result of the complex interaction between biophysical& socio-

economic issues.

Land degradation assessment; an expression for the quality of the land is one form of land

resources assessment & conducted on qualitative& quantitative indicators. Qualitatively the sub

basin classified as; fragile, instable; moderately stable and stable taking climate aridity

&population density as fragility indicators of land degradation. Quantitatively the area was

assessed taking soil erosion hazard as an indicator for quantitative land degradation. To assess

soil erosion hazard for the project area Revised Universal Soil Loss Equation (RUSLE) approach

followed.

The land degradation map developed on ArcGIS environment by using RUSLE parameters

(rainfall erosivity; soil erodibility; slope length and gradient; land cover; and land management

practices) as an input to assess average annual soil loss rate of the area. The mathematical

equation represented on physical based models in the ArcGIS environment. Each variable

overlaid to make the overall spatial analysis. The schematic flow diagram below represents the

interaction and step-by-step activities of the analysis.



SRTMSATELLITE

IMAGE

SOIL

MAP

DEM

IMAGE

ENHANCEMENT

LAND USE

COVER MAP

TERRAIN

PROCESSING

DEM

RECONDITIONING

GROUND

TRUTH

DATA

RAINFALL

R

FACTOR

K

FACTOR

P

FACTOR

MANAGEMENT

PRACTICE

C

FACTOR

SOIL

LOSS

LS

FACTOR

GIS

operation

GIS Analysis

Image

Classification

Flow

AccumulationSlope

Figure 7: Flow diagram for soil loss estimation

The methodology used in this work was the implementation of the Revised Universal Soil Loss

Equation (RUSLE) in a raster GIS environment (or grid-based approach) after some

modifications in the calculation of specific factors. RUSLE developed as an equation of the main

factors controlling soil erosion, namely climate; soil characteristics, topography and land cover

management. More specifically, RUSLEexpressed by the following formula:

Mathematical equation of Revised Universal Soil Loss Equation

A=R.K.LS.C.P ------ (Wischeimer and Smith, 1978)

Where: A= Annual soil loss in tons/ha.yr ; R= Rainfall erosivity;

K= Soil erodibility; LS =topographic factor/slope length and gradient factor

C= soil cover factor; P= Land management factor

Rainfall erosivity (R):

The soil loss closely related to rainfall partly through the detachment power of raindrop striking

the soil surface and partly through the contribution of rain to runoff (Morgan, 1994). This applies

particularly to erosion by overland flow and rills for which intensity generally considered the

most important rainfall characteristics. Erosivity factor for the sub basin was calculated on the



bases of mean annual rainfall data of each station according to the equation given by Hurni

(1985), derived from a spatial regression analysis (Hellden,1987) for Ethiopian conditions based

on the easily available mean annual rainfall (P) and given by a regression equation:

R = -8.12+0.562*P

Where: R= Rainfall erosivity factor, and P= Mean annual rainfall in mm

The mean point rainfall data changed area based by using Thissen polygon method to calculate

erosivity value of the sub basin.

Soil Erodibility (K):

The soil erodibility factor characterizes more or less the soil sensitivity towards erosional force

(Wischmeier and Mannering, 1969, Blume, 1992). Influencing factors of soil erodibility are soil

characteristics such as permeability, infiltration, water-holding capacity, distribution of particles,

aggregate stability, tendency towards dispersion and absorption, transportability, structure, and

humus content. The soilerodibility calculated from the generated soils map of the project area and

raster form used. The erodibility value estimated based major soil type on FAO classification

used.

Slope length and gradient factor (LS):

The slope length and gradient factors estimated from digital elevation model data in the GIS


layer and slope grid layer. The flow accumulation computed from hydrologically corrected DEM

(Digital Elevation Model). Flow accumulation grid represents number of grid cells that are

contributing for the downward flow. The cell size of the DEM represents the length of the cell.

LS= Power (Flow Length, 0.3)/22.13*Power ("Slope"/9, 1.3)developed by (Griffin et al. 1988)

LS= (Flow Accumulation*Cell size/22.13)0.4

*(Sin slope/0.896)1.3

Where: - Cellsize- represents the field slope length

- 22.13 is the length of the research field plot where the equation was derived

Land use/cover (C)

The land cover factor calculated by using the land use/cover map as an input. Each cover value of

the project area synchronized with the adopted C-value in Ethiopian condition. The land

cover/use map was developing from the LandSat Imagery by using Arc-GIS.

Land management practice (P)

The management practice estimated from land use maps and data from biophysical & soil survey.

The P-value estimatedbased on the land cover and slope map of the sub basin supper imposed.



The intersection of the two maps/polygons helps us to determine the P-value spatially though GIS

environment.

Finally, all the five the layers were superimposed and the parameters multiplied according to the

general RUSLE formula. These values gave annual soil loss per hectare per year at pixel level.

Sediment Yield

Considering that only, some of the eroded soils routed to the basin outlet, knowing the ratio

between the basin sediment yield at the basin outlet and soil erosion over the sub basin, sediment

delivery ratio (SDR), is important for the decision makers. The RUSLE calculates soil loss forced

by rainfall but does not consider the SDR. To generate the sediment yield at the outlet, empirical

equations carried out.

SDR = A-0.2

Where SDR:Sediment delivery ratio and

A: area of the Sub basin.

The SDR physically means the ratio of the sediment routed to the outlet over the sub basin, both

overland and channel.



4. RESULT AND DISCUSSION

4.1 Watershed Delineation, Morphology and characteristics

4.1.1 Watershed Delineation

Watershed Delineation: -Efficient management of watershed resource is possible through an

appropriate resource management. Manageable watershed size is required for effective planning

of conservation and maximum production.According to Community Based Participatory

Watershed Development Planning, guideline a total number of 2054 micro watersheds generated.

The micro watersheds delineated based on the standard of the guideline areas started from 250ha.

For the simplicity the sub basin micro watersheds furtherclassified into 22 different sized major

watersheds. Namely Megech, Dirma, Guang, Abagenen_Gayikura, Kima_Trikura, War_Kona,

Merfie, Awelay, Gilgel_Abay, Kilti, Ashar_Agizi_Guder, Jema, Koga, Infranz, Gelida,

Gumara_1,Gumara_2, Rib, Hamus, Shinie, Arno_Garno and Makisegnt_Gumara inorder

toundertake the soil and water conservation measures.

Figure 8: Tana Sub basin major watersheds.

The names of major watersheds confirmed with the communityduring the detail survey and

referred on Top map. The following table(8) shows watersheds in the sub-basin.



Table 8: Major watersheds of Tana sub basin

No Name of watershed Area_Ha % No Name of watershed Area_Ha %

1 Guang 71693.36 5.62 12 Hamus 67961.78 5.33

2 Ashar_Agizi_Guder 116753.24 9.15 13 Infiranz 25159.29 1.97

3 Merfie 10753.12 0.84 14 Jema 48544.91 3.80

4 War_Kona 27789.04 2.18 15 Kilti 73858.57 5.79

5 Arno_Garno 43575.88 3.42 16 Kima_Tikura 20290.7 1.59

6 Awelay 27527.23 2.16 17 Koga 30099.62 2.36

7 Dirma 53127.36 4.16 18 Makisegnt_Gumara 58041.37 4.55

8 Gelda 41853.22 3.28 19 Rib 108811.4 8.53

9 Gilgel_Abay 134600.81 10.55 20 Shinie 30576.2 2.40

10 Gumara_1 82606.19 6.47 21 Abagenen_Gaykura 43148.95 3.38

11 Gumara_2 81330.99 6.37 22 Megech 77828.98 6.10

4.1.2 Morphology

Most of the major watershedrivers are direct tributary of the Lake Tana. The physiographical

characteristics of a watershed influence in great measure its hydrological response and especially

the flow regime during floods and periods of drought. The concentration time, which

characterizes the speed and intensity of the watershed's reaction to a stress (rainfall), influenced

by the different morphologic characteristics. Most of the rivers in the sub basin are increase its

width and depth .This is due to poor management of the upper parts of catchment, the shape of

the watersheds is somewhat irregular and the severity become more dangerous from year to year

4.1.3 Drainage Pattern

The drainage pattern has something to do with erosion hazard and sediment yield. Most of the

major riversstart from the highland of Wogera, Ebinat, Farta, Estie, Dera, SekelaQuarit and

terminates in Lake Tana. Most of the major rivers cross a number of kebeles with in the sub basin

and the Tributaries Rivers join with the major one by traveling so many kilometers. This indicates

that all the parts upper of the watershed contribute high amount runoff to the main channel of

the river simultaneously and significantly, urban areas affect the flood flow characteristics of the

sub basin river. There for, major watersheds are dendritic drainage pattern. Most of the Fogera

and Dembiaflood plain areas affected by Megech, Gumara and Rib rivers stay as flood with a

minimum of 3-5 months during field survey observation and local people explained. This is due

to over top of the riversides and the surrounding areas.



4.2 Fragility Assessment

4.2.1 Climatic Fragility Assessment

Rainfall is the most important climatic factor in determining areas at risk of land degradation and

potential desertification. Rainfall plays a vital role in the development and distribution of plant

life, but the variability and extremes of rainfall can lead to soil erosion and land degradation. If

unchecked for a period, this land degradation can lead to desertification. The interaction of human

activity on the distribution of vegetation through land management practices and seemingly

benign rainfall events can make land more vulnerable to degradation. These vulnerabilities

become more acute when the prospect of climate change introduced.

Rainfall and temperature are the prime factors in determining the climate and therefore the

distribution of vegetation types. There is a strong correlation between rainfall and biomass since

water is one of primary inputs to photosynthesis. Climatologists use an “aridity index” (the ratio

of annual precipitation to potential evaporation) to help classify desert (arid) or semi-arid areas.

Dry lands exist because the annual water loss (evaporation) exceeds the annual rainfall; therefore,

these regions have a continual water deficit. Desserts are the ultimate example of a climate where

annual evaporation far exceeds the annual rainfall. In cases where the annual water deficits are

not so large, some plant life can take hold usually in the form of grasslands or steppes .With

normal climatic variability, in some years the water deficits can be greater than others but

sometimes there can be a several consecutive years of water deficit or long term drought.

The extremes of either too much or too little rainfall can produce soil erosion that can lead to land

degradation .However, soil scientists consider rainfall the most important erosion factor among

the many factors that cause soil erosion. Rainfall can erode soil by the force of raindrops, surface

and subsurface runoff, and river flooding. The velocity of rain hitting the soil surface produces a

large amount of kinetic energy, which can dislodge soil particles. Erosion at this micro scale also

caused by easily dissoluble soil material made water-soluble.



Figure 9:TanaSub Basin Rainfall Fragility

Table 9: Tana Sub Basin Aridity index

N

o

Rainfall

class(mm/yr) Aridity class Coefficient Description Area(Ha)

Coverage

(%)

1 800-1200 Sub humid 0.8 Moderately Stable 469445.15 29.73

2 >1200 Humid 1.25 Stable 1109651.79 70.27

Total 1579096.94 100.00

The sub basin is fall down in to two aridity indices 70.27% of the area is stable and 29.73% is

moderately stable.

4.2.2 Slope Fragility of Watershed

This factor influences soil erodibility in that it controls surface run-off stability of catchment or

watershed classified as follows; catchment considered critical if more than 30% of its land area

has slopes steeper than 50% gradient.



Figure 10:Tana Sub Basin Slope Fragility

Table 10: Slope Index Watershed Stability

No

Proportion of slope above 50 % of

the total catchment area (%) Coefficient Description Area(ha) %

1 0-5 1.25 Stable 557070.99 43.66

2 5-15 0.8 Moderately Stable 392682.27 30.78

3 15-30 0.4 Instable 223530.7 17.52

4 >30 0.1 Fragile 102507.74 8.03

Total 1275791.7 100.00

More than 50% of the total area of the slope proportion fall down in to stable aridity indexand

about 43.66% of the area is stable.



4.2.3 Forest cover Fragility

Forest and bush cover exert the most decisive influence on watershed stability. The proportion of

the forest and bush cover produced from land sat and Spot image and the amount estimated by

using Arc GISand the sub basin classified as critical if:

Forest and bush cover is less than 10% of its total area, and

Forest and bush occurs only in small patches rather than in stands or along lines

Figure 11: Tana sub basin Forest fragility Map

Table 11: Forest Cover as Criteria for Determining Catchment Stability Class

No

Proportion of forest cover of the

total catchment area (%) Coefficient Description Area(ha) %

1 0-10 0.1 Fragile 848325.33 66.56

2 10-20 0.4 Instable 115435.12 9.06

3 20-30 0.8 Moderate Stable 173970.46 13.65

4 >30 1.25 Stable 136841.46 10.74

Total

1274572.37 100.00



The stability of the sub basin by forest factor tends to fragile, 66.56%. The sub basin highly

degraded and fragile from the analysis.

4.2.4. Fragility using Population density

Rising population, soil erosion, undulating topography, and deforestation have contributed to the

rapidly declining soil fertility. The increase in human population to some extent, has also caused

increase in the population of livestock where of the human population is concentrated. The rising

human and livestock populations together have exerted pressure on the natural resources

degradation. In need of fuel and construction, the rural population depended on fully cutting trees.

Population makes the land fragile and make decline in the productive capacity of the land, or its

potential for environmental management, has been a significant factor of the low yield of

livestock in the sub-basin.In the sub-basin, the mean of population density found as 219 people/

km2 area, which is fragile and covers 100.00 % area the sub basin.

Figure 12: Tana Sub Basin Population Fragility Map



4.2.5 Proportion of Arable Land Affected by Erosion

The sub basin of agricultural (arable) fields affected by severe rill and/or gully erosion or show

signs of sheet erosion (exposed stones and / or roots). The border of the sub basin affected with

high amount of soil erosion and fragile. The intensively cultivated areas potential for the fragility

of the sub basin.

Figure 13: Arable land evaluation for classifying watershed stability

Table 12: Arable land as a criteria factor for determining catchment stability class

Arable Land affected by Soil Loss Description Coefficient Area(ha) %

0-5 Stable 1.25 669198.84 52.65

5-15 Moderate Stable 0.8 267406.6 21.04

15-30 Instable 0.4 114364.57 9.00

>30 Fragile 0.1 219955.5 17.31

Total 1270925.51 100.00

According to the analysis, 52.65% of the area is stable, 21.04% is moderately stable, 17.31% is

fragile and 9.00% is instable.



4.2.6 Average farm size fragility analysis

The average farm size of the sub basin is about 1.36ha.This is done based on the sample kebeles

of the socio economic data. However, the analysis of fragility for average farm by taking the

household data of the sample kebeles and the rest kebeles given the average farm size of the sub

basin .Based on this most of the sub basin area is moderately stable.

Figure 14: Average Farm Size Evaluation for Classifying Watershed Stability

Table 13: Average Farm as a Criteria Factor for Determining Catchment Stability Class

No

Average farm

size (Ha) Coefficient Description Area(ha) %

1 <0.5 0.1 Fragile 16211.53 1.27

2 0.5-1 0.4 Instable 52768.82 4.14

3 1-2 0.8 Moderate 1058397.51 82.98

4 >2 1.25 Stable 148121.87 11.61

Total 1275499.73 100.00

From the analysis, the 82.98% of the area is moderately stable and 11.61 % is stable which

shows that the average farmland holding in the sub basin is not as such influence for the fragility.



4.2.7 Total stability the sub basin

After having gathered the information for all indicators above, the respective stability coefficients

entered on general evaluation key to calculate and classify sub basin on stability basis. The six

parameters weighted overlay in Arc GIS environment to get the overall fragility analysis of the

sub basin. From the overall analysis, the sub basin is moderately stable.

Figure 15: Tana Sub Basin Weighted overlay Fragility analysis

Table 14: Tana sub basin weighted overlay fragility analysis

No Description Coefficient Area(ha) %

1 Fragile 0.1 1207.81 0.10

2 Instable 0.4 384429.66 30.30

3 Moderately stable 0.8 881989.34 69.51

4 Stable 1.25 1254.85 0.10

1268881.66 100.00

The overall fragility analysis of the sub basin result shows 69.51% is moderately stable and

30.30% is about instable. This evaluation suggests moderately stable, instable and fragile

condition need detailed management plan.

In order to control the results of the catchment rehabilitation activities, stability evaluation

repeated periodically, every 3-5 years. The result of current/future evaluation compared with the



ones obtained from previous studies. Thus, the success or failure of a catchment's rehabilitation

can easily be determined.

4.3 Land Degradation and Soil Erosion

Land degradation has both on-site and off-site effects. On-site effects are the lowering of either

the productive capacity of the land, causing reduced outputs (crop yields, livestock yields) or the

need for increased inputs. Off-site effects of water erosion occur through changes in the water

regime, including decline in river water quality, and sedimentation of riverbeds and reservoirs.

During field survey, a number of watersheds identified and the degree of degradation is different

for those watersheds. Most of the watersheds seriously affected with free grazing, improper

settlement and land management especially; cultivation of slopes greater than 30% and this lead

to different land degradation problems such as physical, chemical and biological degradation for

sustainability of the watershed is difficult.

Some of the causes of degradation are natural hazards, population growth, expansion of

agricultural lands on to forests and marginal lands, poverty, land ownership problems, political

instability, administration problems and inappropriate agricultural practice. Based on this

different land degradation type observed during field survey at different watersheds with in the

sub basin.

A. Biological Land Degradation

Biological degradation includes loss of biomass, biodiversity, and loss of soil life. The most

common types of biological degradation in Tana sub basin is loss of vegetation cover, loss of

biodiversity and over grazing are the serious one in all woredas of the major watersheds. This

phenomenon is the most widespread and serious feature of agricultural, forest, grass and wetland

of Tana sub basin woredas and almost entirely caused by poor farm management practices.

Biological degradation begins when the natural plant cover of an ecologically balanced soil

system destroyed.

Table 15: Dry matter production from different land covers in the sub basin

Cover type

Average

herbage yield

(ton/ha) Area (ha) % of proportion DM (ton) % of production

Cultivated 1.28 908824.31 72.93 1158751 70.18

Grassland 2.3 150214.49 12.05 345493.327 20.93

Forest 0.5 78179.03 6.27 39089.515 2.37

Shrub land 0.9 102071.16 8.19 91864.044 5.56

seasonal wet land 2.3 6895.61 0.55 15859.903 0.96

Total 1246184.6 100.00 1651057.78 100.00

Source: ADSWE Livestock expert, 2014.



According to the table, 13 shows that high amount of dry matter produced from cultivated land

almost 70.18%,20.93 % from grassland and 5.56 % from shrub and bush land covers this

aggravate biological degradation and high amount of biomass loss from each cover and the

diversity of different land cover decreased.

B. Physical Land Degradation

Many forms of' physical degradation are secondary effects of biological degradation. Tana sub

basin affected by water erosion, stoniness, sedimentation, flooding and crusting of physical land

degradation. Sedimentation, flooding and crusting were observed in the Dembia, parts of Gonder

Zuria and Libokemkem and Fogera plains; Water erosion was observed in the high land of Lay

Armachihoew ,Wegera, Farta, Ebinat, West Belesa, Libokemkem, Alefa ,North Achefer ,Takusa

,Sekela ,Quarit, Fagita Lekoma ,Banja Shikudad, Mecha, Bahirdar Zuria and Chilga woredas.

Figure 16: Sediment deposition near Lake Tana at Takusa and Gonder Zuria Woreda, ADSWE, 2014.

C. Chemical Land Degradation

Chemical degradation due to progressive loss of soil depth of sub watersheds and was observed

plants are bared and over tapped one in their roots. The chemical land degradation is decline in

soil fertility and water pollution of different water bodies. This type of degradation extremely

affect the high land area of Mirab Belesa,Ebinat,Lay Armhachieow,Quarit, Farta,Dera and Estie

with decrease in soil fertility. Around Lake Tana and major rivers chemically affected with water

pollution by different fertilizer and sediment load. The major rivers carried the different types of

chemicals and sediment load from the upper parts of the sub basin.



Figure 17: Soil depth of the sub basin

Figure 18: Shallow Soil depth and Root over top of chemical degradation at Farata (right) and Dera (left)

ADSWE, 2014.



Table 16: Soil depth of the sub basin

Soil depth class Area (ha) %

0-25 131275.4 10.29

100-150 367923.7 28.84

25-50 223713.2 17.54

50-100 352063.8 27.60

>150 200762.9 15.74

1275739.00 100.00

From the analysis table (17) show that 10.29% of the sub basin is very shallow soil depth this

indicates that soil fertility decrease year to year for most steep slope area and different nutrients

removed from the top part of the soil layer.

4.3.1 Water Erosion

Soil erosion caused by water is a common phenomenon becoming a major constraint for Tana

Sub Basin. Soil erosion by water recognized as the principal cause of land degradation and a

major constraint to the development of agriculture. Water erosion experienced in all parts of the

sub- basin. Most part of the sub basin subjected to all forms of water erosion. Every rainstorm

frequent is seen eroding soil in the form of wash as well as soil mass. During field survey, it has

observed dark run off along watercourses. After every rain season, almost all the watercourses

carry large volume of runoff flowing for long period. Regarding the severity of water erosion, its

seriousness increases towards lands adjacent to or bordering the mountains areas of Farta,West

Belesa, Ebinat, Libokemkem, Gonder Zuria, Alefa ,Takusa, Lay Armachihoew, Wogera ,Qaurit,

Sekela, Fagita Lekoma and North Achefer.However, the degree and intensity of erosion varies

from place to place depending on the soil types, and intensity of erosion agents.

4.3.2 Forms of Water Erosion

Soil erosion is not a new phenomenon in Tana sub basin of Amhara Region. The main types of

soil erosion, in the sub basin ismainly water erosion. Most of the highland area of the sub basin

woredas are the source of land degradation. In the sub basin, water erosion is the main type

observed during field survey. Soil degradation is decline of organic matter, depletion of nutrient,

drying up of rivers and lakes.



Figure 19: Tana sub basin organic matter ratinganalysis

Table 17: Tana sub basin organic matter rating analysis

No Rating of OM % Rating description Area Ha %

1 <1 Very low 71611.15 5.61

2 1 - 2 Low 423310.27 33.18

3 2-4.2 Medium 618170.09 48.45

4 4.2-6 High 142073.49 11.14

5 >6 Very high 20659.01 1.62

Total 1275824.01 100.00

The amount of organic matter of the sub basin cover is about 48.45% is medium, 33.18% is low

and 11.14% is high after a few years the amount of organic matter decreased. Because the soil

degradation rate from different land use increased and area, which is not good for agriculture

practice affected by the farmers.

The other case for soil erosion problems in the sub basin is increase in human and animal

population number causes high deforestation, over grazing of hilly areas contributes, and

aggravate soil erosion towards Lake Tana. The sub basin is about a total of 4,225,464 livestock



population. This number indicate that over grazing for the hilly areas and aggravate soil

degradation for the sub basin.

Table 18: Tana Sub basin zonal Livestock population

Zone Cattle Sheep Goats Horses Mules Donkeys

Total

Livestock

population %

Awi 115067 82061 24114 13338 2874 9276 246730 5.84

North

Gonder 900406 282922 191003 3325 3602 87634 1468892 34.76

South Gonder 775760 288885 217005 9569 11115 89861 1392195 32.95

West Gojjam 613880 298114 117656 4864 11497 71636 1117647 26.45

2405113 951982 549778 31096 29088 258407 4225464 100.00

High livestock population 34.76 %, 32.95%, 26.45% and 5.84%at North Gonder, South Gonder,

West Gojjam and Awi zone respectively this lead to high pressure on the hilly areas and facilitate

soil erosion.

The most sever processes of soil erosion observed in the sub watersheds are: Sheet erosion rill

erosion, gully erosion, road and stream bank erosions.

Sheet Erosion: - Sheet eerosion is the removal of thin layer of soil. It is unnoticed because of the

total amount of soil removed in any storm usually is small. It removes lighter soil particles and

soluble nutrients. However, it has serious effect on soil fertility and productivity. Sheet erosion is

the dominant form of erosion observed in all woredas of the sub basin during field survey.

Table 19: Tana sub basin of sheet erosion observed data severity class

Severity class Sheet erosion observation %

Slight 40 54.79

Moderately 8 10.96

Sever 23 31.51

extremely sever 2 2.74

Total 73 100

The result show that 54.79% is slight, 37.51 sever and 10.96% moderately affected with sheet

erosion. As a whole sheet erosion is the dominant form of erosion observed in all woredas of the

sub basin during field survey

Rill Erosion: - is the next noticeable form of erosion, which exists where after sheet erosion

occurs. The symptom of rill erosion is the occurrence of rills or small channels. Rill erosion

occurs in all parts of the sub-basin, considered as the second destructive form of erosion, and

located on relatively hilly slopes and frequent rain.



Figure 20: Rill erosion South Achefer (left) and Dera (right) woredas ADSWE, 2014.

Gully Erosion: - Gully erosion is form of water erosion when small rill channels create gully

through time. Gully erosion has been an ignored serious problem. Because of this, gullies are

regularly expanding and dissect different lands into many plots. It is becoming a common event

in Ebinat ,South Achefer, Dangila, Fagita, Dera, Fogera, Demibia Libokekem and Farta woredas

because of relatively high rainfall and slope. The farmers ploughing their farmlands near to the

gullies. Due to this severity of gully, erosion in the sub basin is increase from year to year and

large amount of hectare affected.

Figure 21: Gully erosion at Ebinat (left) and Farta (right) woredas, ADSWE, 2014.

Most of the gullies occurring in the sub basin can be grouped in to small, medium and sever sizes.

These gullies have the possibilities developed into large gullies due to increase in both depth and

width. According to the field survey and secondary data analysis, gully erosion affects different

types of land cover. This form of erosion affects grazing, cultivated and other types of land use

and 990.7 ha covered with the sub basin.



Table 20: Gully erosion amount by land cover at different depth

Gully depth (m) Amount by Land cover (m)

Grazing land Cultivated land Others Total

Length Width Length Width Length Width Length Width

<1m 55693.03 2.36 92354.03 2.68 13840.48 3.29 161887.5 8.32

1-5m 181974.7 4.86 176006.8 3.84 179009.2 3.85 536990.6 12.55

>5m 52128.82 5.66 35828.03 4.48 31256.4 5.11 119213.2 15.25

Source: Woreda Agricultural office, 2014

Gully erosion is sever in this sub basin and year to year the severity become high and the mount

of soil loss is estimated with volume based and a total of 10251140.84 m3

from different land

cover. From the assessment, high amount of soil loss observed at grazing land, cultivated and

other type of land decreasing order respectively.

Table 21: Gully erosion by volume at different land cover

Grazing land Cultivated land Others

Total Volume L(m) W(m) V(m) L(m) W(m) V(m) L(m) W(m) V(m)

55693.03 2.36 131342.73 92354.03 2.68 247047.02 13840.48 3.29 45541.77 423931.52

181974.7 4.86 2652887.25 176006.8 3.84 2028055.49 179009.2 3.85 2069346.24 6750288.98

52128.82 5.66 1475535.21 35828.03 4.48 803144.89 31256.4 5.11 798240.24 3076920.35

4259765.19 3078247.40 2913128.25 10251140.84

Source: Woreda Agricultural office, 2014

Stream bank Erosion: - Stream bank erosion is a form of water erosion and occurred due to

excess amount of flood, which comes from the high land of Guna ,Sekela,Quarit,Estie

Wogra,West Belesa and Lay Armhachieow, side of the river becomes expanded, and the roots of

trees grown near to riverbank become exposed to further risk. Stream bank erosion is not

understand by the people about its effect but this form of erosion expanded and devastates high

amounts potential areas, irrigation structures, weirs and canals. The area affected by stream bank

erosion may be understand by people are small as compared to other forms of water erosion and

treatment is not usually made because this land is considered as marginal land. Such forms of

erosion at the riverbanks affect the sub basin.

Table 22: Tana sub basin stream bank erosion severity class

Severity Class Stream Bank %

Slight 3 5.56

Sever 26 48.15

Extremely Sever 25 46.30

Total 54 100

Source: Field survey result, 2014.

From the field survey result of table (22) show that 48.15% sever, 46.15 extremely sever and

5.56% is slight in severity

It is also a threat on productive land adjoining rivers. It causes loss of productive mass of soil in

most parts of the sub basin and destroys infrastructures such as bridges and culverts. The area



affected by stream bank erosion may be small as compared to other forms of water erosion and

treatment not usually made because this land considered as marginal land. The farmers expand

their farmland towards the riverbank. Almost all rivers which is found in the sub basin extremely

affected with this forms of erosion and colluvial deposition along the sides of the river banks

Figure 22: Stream bank erosion Alefa woreda (left) and North Achefer woreda (right); ADSWE, 2014.

Roadside Erosion: - Roadside erosion is anotherform of soil erosion. This is due absence of

conservation structures and improper drainage system of the road and the artificial water ways

constructed by different organization are not properly drained towards the natural water ways

.The run off collected and flowing along the road is forming small to medium sized gullies, and

damage both the road and productive land. The areas are affected by such types of erosion are

South Achefer, Fagita, Dangila ,Demibia and Farta due to poor waterway and culvert construction

which cannot hold the amount of runoff. Roads from Koladiba to Gorgora, Kimir Digay to

Simada and Merawi to Dangila suffer high erosion because of absence of conservation structures

and improper drainage system of the road. These roads constructed without regular ditches and

culverts toward the natural waterway.

Figure 23: Roadside erosion Dembia (left), Farta (middle) and South Achefer (right) ADSWE, 2014.



4.4Soil Erosion Hazard Assessment Results

4.4.1 RUSLE Parameters Results

Six parameters are required for the soil erosion estimation, as described previously. All the layers

of R, K, LS, C and P with 90 X 90m output cell size were generated in GIS and were crossed to

obtain the product, which gives annual soil loss (A) for the sub basin. Each parameter of RUSLE

assessed in the following sections.

4.4.1.1 Rainfall Erosivity Factor (R)

The soil loss closely related to rainfall partly through the detaching power of raindrop striking the

soil surface and partly through the contribution of rain to runoff. In this study, the erosivity factor

calculated for each grid cells on the bases of mean annual rainfall43 meteorological stations

distribution of the stations as shown in the figure using spatial analyst tool in GIS environment.

Figure 24: Tana Sub Basin Metrological Stations



Table 23: Mean Annual rain fall and R-values of Metrological Station of the Sub basin

No Station Name

Annual

Rainfall R_Value No Station Name

Annual

Rainfall R_Value

1 Shahura 1214.98 674.70 23 Mekaneeysus 1302.11 723.66

2 Bahir Dar 1436.64 799.27 24 AmedBer 1311.34 728.85

3 Aykel 1164.98 646.60 25 Gassay 1321.88 734.78

4 Dangila 1607.61 895.36 26 Woreta 1274.06 707.90

5 DebereTabor 1547.64 861.65 27 Enfranz 1022.72 566.65

6 Gondar synoptic 1157.29 642.28 28 Makisegnit 1031.50 571.58

7 Chuahit 995.93 551.59 29 AddisZemen 1351.17 751.24

8 TikilDingay 2378.24 1328.45 30 WotetAbay 1599.10 890.57

9 Delgi 814.72 449.75 31 AmbaGiorgis 1030.61 571.08

10 Shembekit 1141.23 633.25 32 Leway 1535.09 854.60

11 KimirDingay 1329.54 739.08 33 Gundil 2412.86 1347.91

12 Yifag 1019.54 564.86 34 Kessa 2529.42 1413.42

13 Aymba 1124.29 623.73 35 Adet 1272.25 706.88

14 Ebinat 899.53 497.41 36 Agere Genet 1601.89 892.14

15 DeraHamusit 1514.18 842.85 37 Askuna 2484.62 1388.24

16 Korata 1593.53 887.44 38 Chanchok 1477.16 822.04

17 Meshenti 1363.95 758.42 39 Deke Estifanos 1712.52 954.32

18 Sekela 1867.94 1041.66 40 Meshenti 1379.88 767.37

19 Zegie 1543.62 859.40 41 Tillili 2030.71 1133.14

20 Chandiba 1272.69 707.13 42 Tiss Abay 1201.99 667.40

21 Gorgora 1036.47 574.37 43 Urana 1960.44 1093.65

22 Wanzay 1502.61 836.34

The mean annual rainfall (P) ofeach station used to calculatethe erosivity factor (R) of the study

area presented below. Each grid cells of mean annual rainfall calculated based on equation

adapted for Ethiopia to get the R-value (rainfall erosivity) using spatial analysis tool in raster

calculator, Arc GIS-10.1 software by IDW method used to generate the rainfall erosivity map. To

make ease of calculation each variables would be changed in to raster form, should have

continuous value. For this data IDW interpolation techniques to change point rainfall to areal

rainfall. Hence, the value we get varies significantly. Therefore, it is used merit to select the best

method by considering the topography of the area, rain gauge density and so on. As shown in the

figure here the map of erosivity values range from 458.15 MJ.mm/ (ha.h) to 1318.35 MJ.mm/

(ha.h).



Figure 25: TanaRainfall and Erosivity Map

4.4.1.2 Soil Erodibility Factor (K)

The soil erodibility factor characterizes more or less the soil sensitivity towards erosion force.

The soil of the study area attempted to classify based on FAO soil unit though soil survey guide

FAO (2006). The K-value of the study area assessed based on FAO soil unit types, textural class

unit and organic matter content adapted from (Robert and Hilborn, 2000) and (Schwab et al.,

1981). The value of K ranges from 0.15 to 0.25 in the sub basin.



Figure 26: Tana Sub Basin Soil and Erodiblity Map

4.4.1.3 Slope Length and Slope Steepness (LS)

The slope length and gradient factors estimated from Digital Elevation Model data in the GIS


layer and slope grid layer. The flow accumulation also computed from DEM (Digital Elevation

Model). The cell size of the DEM represents the length of the cell. Flow accumulation derived

from the DEM after conducting Fill and Flow Direction processes in Arc GIS 10.1 Interfacing

Arc Hydro expression in the raster calculator ofspatial analyst tool.

According to the analysis LS of the sub basin ranges from 0 to 64.81.As slope length and slope

gradient increase the amount of soil loss



Figure 27: Tana Sub Basin DEM, Slope length, Slope gradient and LS Maps

4.4.2.4 Crop Management Factor (C)

The crop management factor represents the ratio of soil loss under a given crop to that of the bare

soil.For this, study Image of Land Sat 8 November and Spot5October 2013 used for analyzing the

c-value. Land cover unit class used for the assessment of crop factor for soil erosion and based on

the assessment the present land use / cover C-value ranges from 0.01 to 0.85 in the sub basin.



Figure 28: TanaSub Basin Crop factor Map

4.4.1.5 Management Practice Factor (P)

The erosion management practice, P value, is also one factor that governs the soil erosion

rate.This is factor governs the amount of soil erosion in the sub basin with in the present land

cover and slope class.Based on the assessment the P-value ranges from 0.1-1.



Figure 29: TanaSub basin Management Practice (P-value) map

4.4.1.6Soil Loss Estimation (A)

All the five the layers were superimposed and the parameters multiplied according to the general

RUSLE-formula. These values gave annual soil loss per hectare per year at pixel level. Based on

the analysis, the total amount of soil loss in the sub basin is about 2833.06 ton/ha/year in

mountains and hilly areas and 0 ton/ha/yr at flat and level areas where deposition takes place,

from 1270952.5hectare with mean annual soil loss of29 ton/ha/yr. The average annual rate of soil

loss in Ethiopia estimated to be 12 tons/hectare and it can be even higher on steep slopes with soil

loss rates greater than 300 tons/hectare/year, where vegetation cover is scant. According to the

analysis, about 73.69% of the area is below the mean annual soil loss of the sub basin.



Figure 30: Soil loss map of the sub basin Table 24: Major watersheds soil loss rate in the sub basin

Major Watersheds

Maximum

value

Minimum

value

Mean

Value

Total area

(ha)

Total loss of

major watersheds

Megech 2764.67 0 23.72 362672.83 8602599.53

Rib 2634.79 0 42.85 250925.25 10752147

Gumara 2464.58 0 35.9 205862.15 7390451.19

Gilgel Abay 2833.06 0 22.49 456331.59 10262897.5

According to the analysis, Rib watershed cover the highest amount mean and total soil loss,

Gilgel Abay watershed is next, Megech is third and Gumara is fourth in decreasing order.

The major watersheds result of study area also falls within the ranges of the findings of FAO

(1984). According to the estimate of FAO (1984), the annual soil loss of the highlands of Ethiopia

ranges from 1248 – 23400 million ton per year from 78 million of hectare of pasture, ranges and

cultivated fields throughout Ethiopia.



Figure 31: Tana sub basin average annual soil loss map

Table 25: Tana Sub Basin Annual Soil Loss

Annual

Loss

T/ha/yr

Average

T/ha/yr Area (Ha) Total T/ha/yr

Area

(%) Description Area (Ha) Area (%)

0 - 5 2.5 669198.84 1672997.10 52.65 None to

slightly 936605.4 73.69 5 - 15 10 267406.6 2674066.00 21.04

15 - 30 22.5 114364.57 2573202.83 9.00

Moderate 178340.2 14.03 30 - 50 40 63975.63 2559025.20 5.03

50 -100 75 72574.88 5443116.00 5.71

High 117467.8 9.24 100-200 150 44892.95 6733942.50 3.53

200-300 250 14698.17 3674542.50 1.16

Very high 38539.03 3.03 >300 300 23840.86 7152258.00 1.88

1270952.5 32483150.13 100 1270953 100



From the assessment the sub basin is about 73.69 % of the area has soil loss fall non to

slight,14.03% moderate ,9.24 % high and 3.03% very high soil loss class respectively

Taking density of mineral soil as 1.65 ton/m3

Total soil loss in tons/ yr = yrtons /13.150,483,32

Density=mass/volume---------------v=m/d

Estimated rate of erosion = yrmmtons

yrtons/365.757,686,19

3/65.1

/13.150,483,32

Soil loss in depth = yearmmyrmm

yrm/55.1/00155.0

201270952500

/365.757,686,19

This implies that 1.55 mm of soil depth washed away per hectare every year withoutconsider the

soil formation rate.

4.4.1.7 Sediment yield

Sediment yield is such important for dams and different schemes projects but it is necessary know

the amount of sediment enter to the Lake Tana also, it tells us how much amount of our top soils

are being eroded by running water.

Area factor =

06.05.1270952

112.02.0

A

Where: A is area of watershed in hectare

SY= (0.06* 19,686,757.65 m3/yr) = 1183990.81 m

3/yr

The main erosion sources in the area are miscellaneous lands around mountains and hilly areas,

cultivated lands; gullies and stream bank formed due to untreated the side of the riverbank and

hilly areas. The amount of sediment yield towards Lake Tana is about 1183990.81 m3/yr. This

lead to decrease the depth of the lake and biodiversity year to year. Finally, the Lake may

disappear with the sediment load and protection may not return the lake.

4.5Causes of Watershed degradation and Soil erosion

The major cause for watershed degradation is land structural deterioration of the project area is

long-term excessive tillage without any remedial measures. Cultivation for a long period, which is

common feature in study area, results in depletion of soil nutrients and organic matter that in turn

enhances crusting, aggressive runoff, accelerated erosion and ultimately low productivity. The

removal of forest cover played a great role in the process of enhancing accelerated erosion. This

was not a terminating single event, rather, a century process. As a result of this process, the



topsoil depth is reduced to a minimum uncultivable value are the most important factors in high

runoff yield that results in more accelerated erosion. The main causes of soil erosion in the

watersheds are the farming system and rapidly increasing human population, the limited area of

fertile soils on flat lands, deforestation, and excessive livestock population.

4.5.1 Population and Land Degradation Processes

Tana sub basin is one of the most densely populated areas.The total population of the sub basin is

about3,158,247 due to the high population of the sub basin; land degradation involves two

interlocking, complex systems: the natural ecosystem and the human social system. Natural

forces, through periodic stresses of extreme and persistent climatic events, and human use and

abuse of sensitive and vulnerable dry land ecosystems, often act in unison, creating feedback

processes, which not fully understood. Interactions between the two systems determine the

success or failure of resource management programs. The problems arise mainly from population

growth and poverty, which caused arable land expansion, intensive land use, deforestation and

over exploitation of the land for short-term benefit.

4.5.2 Deforestation and Overexploitation of Vegetation

Since harvested trees not replaced adequately by tree planting, soils are exposed to high intensity

of rainfall the major sources of energy for the rural households in the watersheds include mainly

firewood. Most households get firewood from scrublands and private eucalyptus plantations

around homesteads and along roads and footpaths. In using the vital energy needs market access

of the nearby urban communities, most charcoal producers in the sub basin resorted to free

gathered biomass fuels, including wood and forest lands along rivers. The removal of vegetation

cover expansion of farmland from bush and forestlands was the other cause of destruction of the

vegetation cover. The total projected demand of forest for 20 years in the sub basin show that an

increase every 5 years interval this will lead high deforestation for the forest area and land

degradation rate increase with deforestation due to demand increase for fuel wood and

construction materials

Table 26: Demand and supply of the existing forest resource projection in the sub basin

Forest resource 2015 2020 2025 2030 2035

Total demand m3 1915301.3 2495625.9 3150082.7 3878673.3 4694718.2

Total supply m3 1499269.8 1499269.8 1499269.8 1499269.8 1499269.8

Difference 3414571 3994896 4649353 5377943 6193988

The demand and supply projection table that thereis a variation between demand and supply

potential of the existing forest resources of the sub basin. The above table show that the demands



exceeds supply by 127% to 316% that means shortage will boost up from 27.8% to 213% within

20 years period. this implies that, unless the existing plantation forests resources will be manage

with improved technologies and supported with additional plantations; also supported by

different energy sources like improved stoves, electric stove, bio fuel, kerosene stoves, solar

energies etc..; the annual incremental potential of the existing forest resource will not be

satisfactory and the degree of unbalance between demand and supply will be extremely go far and

this will create pleasures on the existing natural vegetation. So that this will lead to high

deforestation and aggravate soil erosion in the sub basin.

4.5.3 Improper Agricultural Practice

Causes of land degradation were not only biophysical, but also socioeconomic, example land

tenure, marketing, institutional support, income and human health; most of the soil degradation

problems of the highlands have also been associated with farming systems and farming practices.

Agriculture is the prime means of livelihood for the rural people and remain to be subsistence and

traditional.

A set of improper practices had to do with land expansion, the main problem in Tana sub basin

being the gradual expansion of cultivated lands even to sloping areas.

The local farmers plough areas more than 30% slope for agriculture it is about 36,574.98 ha and

this aggravate soil erosion. Wogera, Lay Armhachieow Libokemkem, Ebinat Farta and Sekela are

the most affected and hilly areas practiced for agriculture.



Figure 32: Slope more than 30% are cultivated in the sub basin

Both human and livestock population growth requires the expansion of interference into new

areas, and the subjection of these areas to the high levels of damage that follow initial

interference. It requires the occupation of sites of lower resilience and higher sensitivity, for

which existing management practices may be inadequate. Degradation then sets in, unless

particular measures taken to protect soil structure and maintain fertility. However, such measures

usually are absent since this kind of practices takes place in situations where low cost solutions

are sought because resources are lacking to invest in land protection. The local farmers are

ploughing now slopes >60% within the upper parts of Tana sub basin woredas Wogera, Lay

Armhachieow, high land of Gonder Zuria, Farta, Libokemkem ,Ebinat, West Belesa, Quarit and

Sekela woredas are the seriously affected.



Figure 33: Improper agricultural practice at Ebinat, West Belesa, Farta and Quarit ADSWE, 2014.

4.6Effects of land degradation and soil erosion

4.6.1 Loss of Soil Mass

Soil erosion is by far the largest process causing land degradation, in the sub basin. The mass of

soil wasting from sheet, rill, gully, streams and roadside assessed as the amount of soil material

that removed from a landscape by water, since these physical changes are obvious and

quantifiable. The total amount of physical soil loss in the sub basin about 19,686,757.65 ton/yr

that causes of land and soil degradation.Due to the poor soils, the process of restoring badly

degraded areas will inevitably be difficult, slow and expensive.

4.6.2 Nutrient Loss

Degradation of the soil resource, on the other hand, has been reported alarming; soil productivity

is declining at the rate of 2-3% per year (Hurni, 1993, cited in Dr Birru 2007) with soil erosion

rate in most croplands usually being far beyond the rate of formation due to cultivation of steeply

sloping lands without adequate SWC measures.

The capacity of the soil in the upper parts of the sub basin to produce crop greatly reduced. Soil

from the top layer is the most concern because it contains more organic matter; rich in available



plant nutrients. This soil is lost in sheet and rill erosion nutrients, which are of great value in

containing nitrogen, phosphorus and potassium. The productivity of cropland is decreasing year

after year at alarming rate. Land productivity is decreasing. The higher yield in production is

associated with fertilizer application, improved seeds and farm expansions from other uses.

Loss of soil fertility severely affected by soil erosion, use of dung and crop residues for household

fuels and animal feeds and decline in fallow periods. Even though the farming system in the sub

basin mixed, crop–livestock, the culture based on the nutrient take way from the soil that the

nutrient return to the soil is minimal.

4.6.3 Hydrological Degradation

Hydrological degradation that include surface and subsurface water declines, seasonality of

discharges of the rivers, variability of rainfall, etc. are important causes and consequences of the

processes of land degradation and challenges for the sustainable land management systems in the

region.

Tana sub basin has many rivers like Megech, Rib, Gilgel Abay and Gumara are the main sources

of water for Lake Tana. However, apart from the main rivers and tributaries, there was hardly of

perennial flow in the sub basin this is due to severe occurrences of soil degradation in the upper

parts of the catchment. This lead to decrease in river flow of water throughout the year and the

local farmers face drinking water for their cattle and themselves in some areas and travellong

distance to get water.

Figure 34: Hydrological degradation Megech at Robit Dembia and Trikura river Takusa woreda, ADSWE,

2014.

4.6.4 Sedimentation

Lake Tana, which is the biggest natural water reservoirs in Ethiopia and affected with sediments a

total of 1,183,990.81m3/yr from all parts of its watersheds; Megech, Rib,Gilgel Abay and



Gumara are the major ones, with high rates. This tragedy of the Lake has international

significance, as the lake is the source of Blue Nile and the home of some endemic animals exist

nowhere except in and around the Lake. There are more pressures and interest conflicts on the

lake aggravating sediment loads to it. Koga, Angerb and Selamko dams and small intake and

weirs are now filled with sediment load year-to-year .This problem is due to improper watershed

management practice with in the sub basin.

Figure 35: Irrigation schemes Selamiko Dam (Debretabor), Drima weir at Dembia and Lake Tana (Gonder

Zuria and Fogera) woreda filled by Sediment load, 2014.

4.7Soil and water conservation Experiencesin the Sub Basin

Conservation is a balance of policies programs plan project and practices that run the gamut from

exploitation to preservation in order to manage the rate of using natural resource in the interest of

bum an kind(Black ,2001) .

By now, most watershed programs have evolved towards participatory watershed development,

decentralizing the planning, implementation and management of soil and water conservation

(SWC) to local communities at the village and Keble level.

The major aged traditional SWC activities include shifting cultivation, soil mulching, slope lands

terracing like Konso culture, soil manuring, and extra water disposal furrows and intercropping.



To improving these traditional conservation measures successfully controlling soil erosion and

the problem of land degradation, the government budget and actions added soil and water

conservation actions started in the country since late 1970s. The government actions have

introduced number of additional technologies and measures, which practiced in the countrywide.

The sub basinpractice different types of soil and water conservation structures traditional as well

as scientific soil and water conservation activities. These structures practiced with the local

farmers (indigenous) and scientific measures assisted by some development programs (NGO‟s)

and regular program (government). During field survey, there are different types of indigenous

and scientific soil and water conservation structures observed(physical and biological).

4.7.1 Indigenous Soil and Water conservation Structures

The indigenous SWC that have been practiced in the sub basin mainly includes soil manuring,

traditional farm-ditches and furrows, traditional Cut-off drains, ,traditional waterway, contour

plough, crop rotation, management of scattered trees on croplands, hedge rows and live fences

along farm boundaries and grass strips along farm boundaries. The farmers belief on the

importance and advantages of the traditional SWC practices are categorized under three groups;

1) soil fertility improvement, 2) safe removal of excess water from farmlands, protecting

farmland from run-off coming from up slope lands. Farmers in sub basin practiced diversion-

drains and waterways to divert run off coming from up-slopes and to collect run-off coming from

farm ditches. The farm boundaries of most farmers have also bordered by traditional bund and

traditional waterways. Traditional cut-off drains are mostly located at the upper age of the farm

boundary, while waterways are located along the farm boundaries if the boundary bordered along

the slope of the land. In most cases, the traditional ditches are temporary structures constructed

every rainy season. However, with in the sub basin some permanent structures observed during

field survey and still existed.

These indigenous/traditional SWC measures have been contributing a lot in reducing soil erosion

and controlling run off and floods. However, some physical structures such as cut-off drains,

waterways and farm ditches are aggravating soil erosion problems in adjacent farmlands because

they collect run –off from up-slopes and pass high run –off to the down slopes that create gullies

in the downstream areas. Waterways, which are supposed to carry a large amount of runoff from

traditional cut-off drains and farm ditches, are bare, gullies without check dams, grasses or stone

paving problem observed. As per the farmers view, these were happened due to land



fragmentation, lack of disposal areas and unwillingness of some farmers to accept and pass run-

off coming from upslope and adjacent lands towards the natural waterway.

The problems are associated with technical, social and management factors. Even, some problems

require policy considerations. Thus, it is highly important to reduce those drawbacks of

indigenous SWC measures.

4.7.2 Physical Soil and Water Conservation Structures

Many new physical and biological SWC technologies introduced since late 1970s in Ethiopia.

Most of the newly introduced common technologies adapted and implemented in Tana sub basin

mainly physical soil and water conservation measures. These include farmland soil, stone-faced

soil and stone bunds, which are mainly graded and level types and hillside terraces.Moisture

conservation measures like micro basin, eyebrowbasin and trench.Flood control like cut off drains

and waterways. Gully control mechanisms likesack, stone,brushwood and gabion check damsare

the most common practice technologies. The physical soil and water conservation structures

constructed with in the sub basin most structures are not follow watershed based approach and

poor quality. Some of the areas are good in quality and watershed based approach like Gonder

Zuria Minzro, Takusa, North Achefer Amishan Jihan, Mecha, Farta woreda Huletu Simina and

Mynet kebele, Sekela Lijambera kebele are model works. The implementation of these SWC

measures done through the assistance of lay out farmers, developmentagents and in some cases

the woreda level experts in design and layout of structures. These agents and experts also train

farmers in the SWC technologies application and the trained farmers, team leaders and support

the development agents in lay out of structures and kebele and woreda carbine

membersmobilizing the communities to participate in the implementation of SWC measures.

However, the technical support of the experts are so scant that most of the constructed physical

SWC structures lack the capacity to control soil erosion effectively. Their capacity further

impacted by geophysical and socio-economic situations of the area. Woreda agricultural offices

report that some of the physical SWC structures particularly in farm fields disappear every year

because of partly design and layout failures, improper farming operation, free grazing system,

lack of maintenance and upgrading works and partly because of steep slopes that produce heavy

floods.



Figure 36: Physical Soil and Water conservation at Farta, Mecha, Takusa and Fagita woreda, ADSWE, 2014

4.7.3 Biological Soil and Water Conservation

Biological SWC measures are limited to tree planting mainly with eucalyptus globules tree

species on farm boundaries, along roads and footpaths and along streams and rivers in addition to

fuel wood plantations around homesteads. Even this plantation is not under the objective of SWC

but rather the initiative and push from farmers. Biological SWC measures like grass strips and

alley cropping; cover cropping and green manuring; multiple cropping; hedgerows planting; relay

cropping and agro-forestry farming system are not significantly practiced except some such as

hedgerows, grass strips and inter cropping are practiced in traditional basis.

However, the ecology of the area is suitable to grow diversified type of trees and shrubs.The sub

basin is highly affected withincreasing human and livestock population and free grazing;

extensive field crop production; low awareness of most farmers; inadequate extension services;

lack of planting materials; decreased land holding size are the major factors for low adoption of

biological SWC in the sub basin.



Figure 37: EffectiveBiological Soil and water conservation Sekela and Fara ,ADSWE 2014.

As the experience shows that soil and water conservation structures started in the sub basin during

Dergue Regime but the sustainability is not profitable and now it starts in 2001 E.C.in a new

strategy at Regional level to do the physical and biological conservation structures. The soil and

water conservation structures results show that most structures not done in standards, the quality

is less and sustainability become well. The structures done by cooperating the development group

and work group at kebele level. In addition to this, the structures done by the local peoples given

(assigned) by the kebele land administration for the owner of management. The amount of work

not fit with the standard of work norm of the structures. Some woredas small amount of work

when compare with the number of population participated and on the other hand the large amount

of work with less participated population. During field survey most of the structures failed with

free grazing and poor management what observed. (Table 20) shown that below physical soil and

water conservation structures a little bit better area coverage but biological soil and water

conservation is less in coverage area with in the sub basin. Area closure and gully treatment with

in the sub basin is now better from year to year this is due to watershed based approach practice

done. Moisture conservation structure like micro basin, eyebrow basin and trench started and the

coverage is better year to year for the sub basin, which helps, from prevention of land degradation

and moisture harvest.



Table 27: Total Achievement of SWC from2001-2005 EC with in the sub basin

No Woreda

Identified and

studied Micro-

watershed

Physical measures Biological measures Water conservation Gully

control,

check dams,

m3

Terracing,

km COD, m3

Plantation

on bunds,

km

Plantation

on gullies,

ha

Area

closure, ha

Micro-basin

,No

Trench,

No

Eye-brow,

No

1 Alefa 14 4229.76 203.00 227.52 0.00 439.00 3530 7754 0 688.00

2 Takusa 18 12689.28 4.99 449.28 4.75 4587.00 294500 65600 28300 36000.00

3 Chilga 60 11674.35 143.76 76.53 10.25 834.89 3336 2533 910 31122.25

4 Wegera 9 1699.46 0.00 0.00 0.13 80.00 0 2316 100 0.00

5 Lay Armachew 32 7208.26 70.84 4427.76 0.00 620.62 72977 174205 3800 88.02

6 Gonder Town 0 5375.94 79.55 0.40 2.21 702.99 6873 20064 831 27.19

7 Gonder zuria 103 6892.80 4007.00 301.44 15.00 4149.00 41075 65460 365 0.00

8 Demibia 30 14935.23 0.00 0.00 0.00 653.00 441 1770 1106 5949.00

9 Libokemkem 123 14081.29 49843.20 186.43 42.18 1780.38 228534 441359 31015 581879.00

10 Fogera 152 19068.68 43.08 2898.96 10.13 1738.25 90995 178704 15083 142643.01

11 Ebinat 13 2273.67 0.16 0.00 0.00 2113.00 886 20406 11915 8468.80

12 Farta 228 22756.00 358.10 303.00 63.30 3580.00 353848 303917 124227 436.67

13 Banja 7 23497 250.66 0 154.6 4514.65 6447 75564 1270 257.6

14 Fagita Lekoma 95 46259 1025 34113 3258.5 10000 308 79624 0 633.49

15 Dangila 157 32945 472 1374.465 271 1696 499 69460 0 160.095

16 N/Achefer 208 41439.66 435.14 34262.6 212.7 4415.45 0 31575 126916 640

17 S/Achefer 71 39000.4 170.65 21428.6 105.3 619.24 9287 54016 1705 116.3

18 Mecha 352 57538.7 583.198 77538.7 377 107 0 260364 78698 0

19 Bahirdar Zuria 145 25343.4 131652 330.81 370.02 0 932 8131 0 55374

20 Bahir Dar Town 0 389.82 3977.5 0 0 46 0 350 0 3375

21 Sekela 0 143610 52495 0 0 0 1408 362749 0 20143

22 Dera 198 44651 316.7 9086.1 0 4864.6 0 1520434 904656 1215822

23 Estie 9 4366.76 1280 0 48 285.57 5719 25488 1087 102296

Total 2024 581925.45 247411.52 187005.59 4945.07 47826.64 1121595 3771843 1331984 2206119.43



5. PROBLEM IDENTIFICATION

Watershed management in Ethiopia is a serious problem in general, in the Amhara Region

particularly Tana sub basin characterizedbyland degradation, deforestationand over grazing.

Fieldobservations at numerous points in the watershed indicated that physical and biological

degradations are the common phenomena of sub basin. For most of the part of sub basin, land

degradation and fertility losses mainly attributed tothe following major factors.

5.1 Soil Erosion and Land Degradation

Soil erosion by water is high in the sub basin.Even though erosion process is subtle one,

itevaluated by its effect on cultivated lands and check dams. Uncontrolled erosionfinally leads to

land deterioration.

The major causes of soil erosion and land degradation are:

Natural features such as rugged topography, temporal high intensity of rainfall.

High population growth is pressure on land for cultivation and encroachment of

cultivation to marginal lands (i.e. steep slopes, forestlands, grazing lands, etc.)

without conservation measures.

Over grazing and over stocking and continued lack of proper management of

communalgrazing lands and lack of attention to animal feed production by any

concerned agencies.

Lack ofland useresponsibility.

5.2 Deforestation

Excess removal of forests is contributing to land degradation. Since harvested trees notreplaced

adequately by tree planting in the region, soils are exposed to high intensity of rainfallthe major

sources of energy for the rural households in the watershed include mainly firewood. The only

sources of fuel wood therefore are some homestead plantations, crop residues andanimal dung.

The major sources of energy for the rural households in the watershed includemainly firewood

residues. Most households get firewood from scrublands and private eucalyptusplantations around

homesteads and along roads and footpaths.



5.3 Decline of Soil Fertility

Loss of soil fertility severely affected by soil erosion and land degradation, use of dung andcrop

residues for household fuels and animal feeds and decline in fallow periods. Even thoughthe

farming system in the project area mixed crop–livestock, the culture based on thenutrient take

way from the soil that the nutrient return to the soil is minimal. The chemicalfertilizer use is also

limited because of its unaffordable price to the watershed area poor farmers.

The soil fertility problem in the watershed is therefore one of the serious problems, which

shouldbe addressed in this watershed management plan.

5.4 Weak Soil and Water Conservation Work and Management Practice

There is no defined land use system followed in the region. For the last many years, this has led

over exploitation of the natural resources. It is an area where the government and the public

should agree and adopt a policy for further degradation avoid.

The soil conservation programs were target-driven requiring procedures completed in scheduled

time with the result the officials concerned could not integrate themselves with the community.

There was no training component for the beneficiaries. The beneficiary participation confined to

preparation of action plans and no stakeholder contribution envisaged resulting in lack of

involvement.

Soil and water conservation works were focus only area coverage during construction time, even

the activity mainly targets on physical soil conservation measures, the quality was not well

controlled, no proper design, farmers little awareness, mass mobilization problem, female

participation for work is less, free grazing and unwillingness and proper maintenance is not

undertaken by the farmers on time which is devastated during land preparation.

At this time, different soil water conservation practiced but poor management observed with in

the sub basin like Mecha, Dera, Gonder Zuria and Libokemkem severely affected free grazing

and poor management design of structures and farmer plough during agricultural practice.



Figure 38: Poor SWC practice and management Gonder Zuria, Dera and Libokemkem ADSWE, 2014.



6. LAND MANAGEMENT PRACTICES/OPTIONS

6.1 Capability Land Classification

The variability of land resources and farming system would mean variable problems and

constraints spatially distributed with in the watershed. Variations in soil type, depth, slope and the

like factors have a strong influence on agricultural land husbandry practices. It is therefore,

necessary to classify similar areas within the watershed based up on physical land resources and

socio-economic characteristics. One of the most widely used systems of land classification is that

of the Soil Conservation Service (SCS) of the U.S. Department of Agriculture (USDA). It

commonly referred as land capability classification. There is no one land capability classification

(LCC) but many (Taffa, 2002). Different countries have different classification system, for in

every country or geographical region there are different factors, which allowed for (Taffa, 2002).

Although the numbering of classes is similar in each of the systems, this does not necessarily

mean that the lands are the same. Land in class II in Ethiopia, for instance, may not be the same

with that of class II in U.S.A or Israel (Berehanu, 2001). The land capability classification

adopted here is the one developed to the Ethiopian condition by J.V Scobedo (1988).

Accordingly, the land evaluation targeted to assess the capacity of land for soil and water

conservation purposes. The input data for capability classification obtained from soil and

topographic survey assessment report. Data of slope, soil depth, erosion, water logging, drainage,

and texture obtained from soil survey and land degradation assessment organized in soil mapping

unit over the study area. Each thematic map were reclassified based on the land capability rating

table and mapped which further combined in Arc GIS environment for capability classification.

This takes account of the least favorable assessment as limiting or determined by lowest supply of

land to evaluate the capacity of land for major land uses under consideration.

6.1.1 Capability Inputs

The present land capability evaluation used slope percent, soil depth, erosion, drainage, surface

texture, obtained from different surveys of this report sources and the present study and

reclassified based on the factor-rating table given in below.

6.1.1.1Slope (%)

Slope of the study area generated from 90mx90m DEM reclassified in Arc GIS environment and

calculated for proportional area coverage.



Table 28: Table Slope factor rating and proportional area coverage

No Description Slope class Range Code Area(ha) %

1 Flat 0-3% L1 380617.12 29.83

2 Gently sloping 3-8% L2 380112.37 29.79

3 Sloping 8-15% L3 222498.43 17.44

4 Moderately steep 15-30% L4 199645.89 15.65

5 Steep 30-50% L5 75676.25 5.93

6 Very steep >50% L6 17241.76 1.35

1,275,793.00 100.00

6.1.1.2 Soil Depth

Soil depth data were directly obtained from the present soil survey, classified very shallow (V),

shallow (S), moderately deep (M), deep (D) and very deep(X) and summarized as under.

Table 29: Soil depth rating and proportional area coverage

No Description Soil depth (cm) Code Area (ha) %

1 Very deep >150 D1 200762.9 15.74

2 Deep 100-150 D2 367923.7 28.84

3 Moderately deep 50-100 D3 352063.8 27.60

4 Shallow 25-50 D4 223713.2 17.54

5 Very shallow 0-25 D5 131275.4 10.29

Total 1,275,793.00 100.00

6.1.1.3 Soil Erosion

The soil erosion rate estimated from the RUSLE model and rated accordingly as in table below.

Table 30: Soil erosion rating table

Soil Loss T/ha Description Area Ha Area (%)

0 - 5

None to slightly 940131.86 73.69 5 – 15

15 – 30

Moderate 178993.76 14.03 30 – 50

50 -100

High 117883.27 9.24 100-200

200-300

Very high 38656.53 3.03 >300

1,275,793.00 100.00

6.1.1.4 Soil Drainage

Input data of infiltration for land capability classification defined based on internal soil drainage

classes of the study area during field soil survey and rated accordingly as in table below.



Table 31: Soil drainage class of Tana sub basin

No Drainage class Area (ha) Cover (%)

1 Excessively drained 84781.55 6.65

2 Imperfectly drained 337632.10 26.47

3 Moderately well drained 294377.33 23.08

4 Poorly drained 11051.8 0.87

5 Rock and Water body 26600.70 2.09

6 Somewhat Excessively drained 187393.91 14.69

7 Well drained 333901.61 26.17

1,275,793.00 100.00

6.1.1.5 Soil Texture

Soil texture classes of the study area rated and classified into 13 textural types obtained from soil

laboratory analysis. From the analysis, the three textural types are dominant in the sub basin

49.77% clay, 17.01% clay loam and 14.49% clay-to-clay loam respectively.

Table 32: Soil texture class distribution of study area

No Texture Area (ha) %

1 Clay 634972.18 49.77

2 Clay loam 217017.02 17.01

3 Clay loam to sandy clay 65585.32 5.14

4 Clay to clay loam 184886.52 14.49

5 Clay to silt clay loam 2507.39 0.20

6 Clay to silt loam 11038.16 0.87

7 Loam 33084.38 2.59

8 Sandy clay 42369.02 3.32

9 Sandy clay to clay 1214.63 0.10

10 Sandy loam 56212.40 4.41

11 Silt clay 3.81 0.00

12 Silt loam 247.46 0.02

13 Water body and rock 26600.71 2.09

1,275,793.00 100.00

6.1.2 Land Capability Classes

Land capability assessment utilized soil information obtained from field survey to classify the

land based on capability concepts of maximum limitations. In this regard, land capability maps

were prepared based on the capability assessment criteria and used to determine the conservation

needs; understand the basic characteristics of the soils and climate used as a background

document for the preparation of soil and water conservation plan in the study area. In general, the

capability class maps produced for the study area presented below in figure 40.



Figure 39: Land capability class map

Table 33: Land capability class and proportional area coverage in Tana sub basin

No Capability class Area(ha) Coverage (%)

1 I 84184.2 6.60

2 II 171823.4 13.47

3 III 197974.4 15.52

4 IV 520721.7 40.82

5 V 31791.85 2.49

6 VI 165832.6 13.00

7 VII 49311.26 3.87

8 VIII 54153.58 4.24

1275793.00 100.00



6.1.2.1 Land Capability Class I

This class covers 84184.20ha of land and accounts 6.60% of the study area. The soils do not have

limitations or hazards that restrict their use and suitable for a wide range of crops. They cropped

very intensively, used for pasture, range, woodlands and wildlife reserves. The soils are deep,

well drained, and the land is flat to gently sloping and generally fertile.

The soils need only commonly used crop management practices such as contour plough, grass

strip, trash line, land preparation, manure and fertilizer application and weeding to maintain their

productivity.

6.1.2.2 Land Capability Class II

Land capability class II occupied 171823.4hectares of land accounted 13.47% of the basin. Soils

in class II have limitations that reduce the choice of plants or require moderate conservation

practices. Soils in this class require careful soil bund, stone bund and stone faced soil bund and

biological soil conservation ,soil management and conservation practices to prevent deterioration

or to improve air and water relations when the soils are cultivated.

6.1.2.3 Land Capability Class III

This class consists of 15.52% of the study area occupied 197974.4hectares of land. The major

limitations of this class include slope, erosionand soil depth. It is, therefore, obvious that the soils

in Class III have combinations of limitations that reduce the choice of plants or require special

conservation practices.

6.1.2.4 Land Capability Class IV

The soils and climatic conditions in this class used for cultivation, but there are very severe

limitations on the choice of crops. In addition, very careful management is required. This class

covers 520721.7hectares, which is 40.82% of the land area of the basin.

6.1.2.5 Land Capability Class V

The most limiting factor of these soils is poor drainage. Soils in classes V to VIII are generally

not suited for cultivation. In some waterlogged areas of this class, drainage is not feasible. Often

water loving crops such as rice, dry season grazing or pasture development is feasible on this

class of land. Assessing the class in the basin have 31791.85hectares and covers about 2.49%

area.



6.1.2.6 Land Capability Class VI

Soils in this class have extreme limitations that restrict their use other than grazing, forestry and

wildlife. This class covers about 165832.6 hectares, which is 13.00 % of the study area.

6.1.2.7 Land Capability Class VII

The major limitations of the class are soil depth, slope, and erosion. Soils in this class have very

severe limitations, which restrict their use to grazing. It used for limited forestry and wildlife.

This land capability class occupies 49311.26 hectares and accounts about 3.87% of the sub basin.

6.1.2.8 Land Capability Class VIII

The major limitations of the class are soil depth, erosion and slope. The soils in this land

capability class not used for commercial tree planting. Their use should be restricted to recreation,

wildlife or aesthetic purposes. This land capability class occupies in the study area, which is

54153.58 hectares that accounts for 4.24 % of sub basin.

6.2 Proposed Soil Water Conservation Measures

In the sub basin high amount of soil loss estimated so that to solve the problem land use

management options proposed as an intervention those are mixture of physical and biological

conservation measures should be done. The interventions should be watershed based, vary with

slopes, current situation and suitability to the farming systems of the specific areas. During

implementation of the land management components in the micro-watersheds, however

interventions and land uses preferred by slope classes and land types by the land users take care

of to satisfy the participation of the farmers and their demands in integrated watershed

development.

In Tana sub basin, land degradation and status of soil erosion assessed based on review of

previous studies and actual field survey. During these periods it was possible to realize the core

causes of the problems and as well as the efforts made to alleviate the problems. In the sub basin,

physical structures constructed especially on the flat slope of grazing land areas and different

physical structures under taken by financial assistance from NGOs and government. These efforts

were lacking integrated approaches and consistencies in type and structure and thus most of the

efforts were not successful.

In order to solve the problem of soil and water conservation structures in the sub basin different

physical and biological conservation, structures proposed based on slope and land use land cover.



As you know, the sub basin rugged and undulating topography so that different soil and water

conservation structures are proposed. Such as soil and stone bunds, micro basin, eyebrow basin,

trench, percolation pit, hillside terrace, bench terrace, area closure and bund plantation. These

structures are conserve moisture, increase biomass of the sub basin and the most important ones.

In view of those facts, we realized that those structures already at the place maintained through

biological interventions: through plantation of different multipurpose tree and shrub species (e.g.

grass species, agro forestry). Therefore, nursery establishment is the first priority as a project

component. It expected that this intervention will mitigate the current offsite and onsite impacts

of soil erosion and at the same time tackle the root cause of erosion such as tree clearing for

firewood and construction.

The improper road ditch channel construction, overgrazing and deforestation aggravating the

gully formation and reduce grazing lands. Some of the gullies that treated by simple intervention.

The check dams supported by gabions, as the soil is easily erodible and not stable. Promotion of

agro-forestry also identified as project for its multipurpose for the community: e.g. soil fertility

management and fodders for animal feeds. Additional physical soil conservation measures such

as cut off drain at the top of gully recommended protecting growth of the gully with close

supervision of the development agents in sub basin and the physical structures done with

consultation of group of farmers so that they can do the work in common consensus.

Different physical and biological measures selected in the sub basin to address the problems of

soil erosion and land degradation. Their application follows the slope and suitability of the

techniques to area and farming system

For sound watershed management different interventions proposed that will solve the

statedproblems when it implemented properly. The development plan designed considering

social,economic, technical and ecological aspects of the area. Based on this, the

watershedmanagement plan covers physical, biophysical and biological conservation measures.



Figure 40: Proposed soil and water conservation measures

Table 34: Proposed Soil and water conservation measures

No Proposed SWC Area(ha) Coverage (%)

1 Area Closure 354201.9 27.76

2 Bench Terrace 41151.68 3.23

3 Buffering 31791.85 2.49

4 Contour Trench 29201.89 2.29

5 Grass Strip 245978.61 19.28

6 Micro Basin 44278.65 3.47

7 Soil Bund 75641.74 5.93

8 Stone Bund 97610.49 7.65

9 Stone faced Soil Bund 298102.4 23.37

10 Trench 57833.83 4.53

Total 1275793.00 100.00



6.2.1 Physical Soil and Water Conservation Measures

Physical SWC measures recommended in thesub basin for erosion control include soil, soil

facedand stonebunds, cut off drains, waterway, check dams, hillside terraces, micro basin,

eyebrow basin, bench terraceand trenches.These physical measures are applicable in a broadrange

of agro-ecological zones and land uses.

1. Soil Bunds

Suitable mostly in semi-arid and arid parts of the country but also in medium rainfall areas with

well drained soils. The sub basin suitable for soil bund is about 75641.74 ha and covers 5.93%.

The bund reduces and stops the velocity of runoff and consequently reduces soil erosion. Several

areas also show-introduced bunds adapted or adopted from past conservation activities. Local

experience is very relevant to assess performance of past activities and suggest modifications as

required. Improved designs integrated with local ones to add strength to bunds (grass, stones, etc).

It applied on cultivated lands with slopes above 3% and below 15% gradient and grazing lands

with gentle slopes at wider intervals (up to 5%) and applied within sloping homestead areas

combined with cash crops.

2. Stone Bunds

It is suitable in semi-arid and arid parts of the country but also in medium rainfall areas with deep

and well-drained soils. The area suitable for stone bund is about 97610.49 ha, covers 7.65% and

stone-faced soil bund 298102.4ha, and covers 23.37%. The stone bund reduces and stops the

velocity of runoff and consequently reduces soil erosion and the steady decline in fertility and

crop yields. Several areas also show-introduced bunds adapted or adopted from past conservation

activities. Local experience is very relevant to assess performance of past activities and suggest

modifications as required. Improved designs integrated with local ones to add strength to bunds

(plants, etc). It is applicable in a broad range of land uses in all agro-climatic areas, particularly in

cultivated lands with some level of stoniness and common in treatment of degraded hillsides.

Stone bunds also possible in large gully networks combined with vegetative stabilization and tree

planting.



Figure 41: Cross section of a bund

3. Cut off drain

A cut-off drain is a graded channel constructed to intercept and divert the surface runoff from

higher ground/slopes and protect downstream cultivated land or village. This safely divert the

run-off to a waterway, river, gully, etc. After assessing existence of enough out let facility, cut-off

drain is effective to avoid the excess runoff from cultivated lands.

t is suitable at a foot of a steep hillside under which cultivated fields are exposed.

Constructed above gully head to divert off run off from active gullies to treated/stable

ones.

4. Water way

A waterway is a natural or artificial drainage channel constructed along the steepest slope or in a

valley to receive/accommodate runoff from cut-off drains and graded terraces/bunds. The

waterway carries the run-off to rivers, reservoirs or gullies safely without creating erosion.

- A vegetative waterway constructed in areas without stones. The main advantage is that

waterways constructed for both very small and large size catchments, thus accommodating

individual or communal needs for drainage and evacuation/use of excess run-off.

-Paved waterways are suitable in steeper terrains and areas with large amount of stones

5. Micro-basins

Micro basins are small circular &stone-faced structures for tree planting. Are suitable for medium

and slightly low rainfall areas, stony areas and shallow soils .Based upon experience they are not

very effective in low rainfall areas (where trenches, eyebrows, etc. are preferred). It is applicable

in steep and degraded hillsides (max slope 50%) and for community closures. Micro basins often

combined with other measures such as hillside terraces, stone bunds, trenches, etc. Micro-basins

proposed to accommodate eroded soils and runoff water to create conducive microenvironment

for any type of plantation activities. The sub basin area suitable for micro basin is about 44278.65



and covers 3.47%.The shape of micro basins can be full or half moon type. For flat areas, full

moon type recommended while half-moon is for steep slopes. It is applicable in steep and

degraded hillsides and for community closures. Combined with hillside terraces, trenches and

other measures. Constructed using sods, in areas without stones, stabilized with

plants.Constructed using sods, in areas without stones, and stabilized with plants.

B

S

Figure 42: Patterns of micro basins

6. Trenches

Trenches are large and deep pits constructed along the contours with the main purpose of

collecting & storing rainfall water to support the growth of trees, shrubs, cash crops and grass or

various combination of those species in moisture stressed areas (350-900 mm rainfall).Trenches

can have flexible design, to accommodate the requirements of different species. Trenches collect

and store considerable amount of runoff water, thus vegetation grows faster and vigorous.

Trenches protect cultivated fields located downstream from flood and erosion. The area suitable

for trench in the sub basin about57833.83 ha and covers 4.53 %. Part of the water captured by the

trenches reaches the underground aquifer. Therefore, water tables recharged and supply springs

and wells with good quality water and for a long period. It is highly suitable in many areas in the

highlands to improve closures and plantations. Also relevant in pastoral areas to improve grazing

reserves, aerial pasture, etc. Easily understood /adopted after demonstration. Trench is applicable

in steep and degraded hillsides and for community closures. It combined with other measures

such as hillside terraces, stone bunds, and trenches based upon soil, slope and stoniness and

applied inside large gully areas for tree planting.

7. Bench terraces

A bench terrace is a conservation structure where a slope converted into a series of steps, with a

horizontal cultivated area on step riser between two steps. In Ethiopia, either constructed directly



on a slope or gradually developed from bunds and fanya juu. They are level along the contour in

dry to moist agro climatic zones. In moist to wet areas, they graded to drain excess runoff to

waterways or river. The area suitable for bench terrace in the sub basin is about 41151.68 and

covers 3.23%.

Specifications: Slope up to 50%, soil very deep, vertical interval is two and half times the depth

of re-workable soil depth.

Table 35: The gradient, soil depth and width of a cultivated area (in meters) on a bench terrace.

Slope gradient %

Soil depth in (cm)

25 50 75 100 125 150

20 2.81 5.63 8.44 11.25 14.06 16.88

30 1.77 3.54 5.31 7.07 8.85 10.63

40 1.25 2.50 3.25 5.00 6.25 7.50

50 0.94 1.88 2.81 3.75 4.69 6.63

Note: Bench terraces employed when too steep slope land is to be cultivated. Therefore, bench

terraces are not preferable in shallow soils. During digging infertile subsoil brought up to the

surface unless special measures taken.

- An enormous amount of labor is required for the construction, so that valuable crop should

be grown.

-They constructed on the contour or with slight gradient; the difficulty is to discharge any surface

runoff down the steep slope without causing erosion

8. Gully Control and Rehabilitation

Stabilization of gullies involves the use of appropriate structural and vegetative measures in the

head, floor and sides of the gully. The combination of the two measures (biophysical approach) is

the best solution for effective gully control and productive use of the gully area. In the sub basin

990.7ha gully assessed from cultivated, grazing and other types land use.For this physical and

biological treatment must done. The establishment of biological measures will follow the

construction of gully physical structures. Stabilized watershed slopes are the best assurance for

the continued functioning of gully control structure.Some of the most common physical and

biological gully control measures.

In gully control, temporary physical structural measures such as gully reshaping, brushwood, sand

bag, loose stone, and gabion check-dams used to dissipate the energy of runoff and to keep the

stability of the gully. Check-dams constructed across the gully bed to stop channel/bed erosion.

By reducing the original gradient of the gully channel, check-dams diminish the velocity of water

flow of runoff and the erosive power of runoff. Run-off during peak flow conveyed safely by

check-dams.



a. Gully reshaping and filling

Gully wall reshaping is cutting off steep slopes of active gully flanks in to gentle slope (Minimum

at 45% slope), up to two-third of the total depth of the gully and constructing small trenches along

contours for re-vegetating slanted part of the gully walls and beds. If the gully is wide and has

meandering nature with huge accumulation of runoff flowing down, cut off soils and soil

materials can be washed away by runoff water and requires constructing of retaining walls, to

protect displaced (not yet stabilized) soils and soil materials and newly created sidewalls of the

reshaped gully. Gullies with very little water flow stabilized by filling and shaping, that is, if the

surface water diverted, and livestock kept out. Steep gully heads and gully banks shaped to a

gentler slope (about a one-to-one slope). Filling of gullies is applicable only for small

discontinuous gullies, in their early stages of development. The filled gully area can be planted

even be used for cultivation. Rills and incipient branch gullies filled in by spade shovel or plow

(on cultivated lands)

b. Brushwood check-dams

Brushwood check-dams made of posts and brushes placed across the gully (Figure 5). The main

objective of brushwood check-dams is to hold fine material carried by flowing water in the gully.

Brushwood check dams can also stabilize small gully heads, no deeper than one meter.

Brushwood check-dams are temporary structures and not used to treat ongoing problems such as

concentrated run-off from roads or cultivated fields. They employed in connection with land use

changes such as reforestation or improved range management until vegetative and slope treatment

measures become effective.

There are two types of brushwood check-dams: these are single row and double row brush wood

check-dams. The type chosen for a particular site depends on the amount and kind of brush

available and on the rate and volume of runoff.

i. Single row brushwood checkdams

These check-dams used where the flow of runoff is less than 0.5m3/sec. The structure is

temporary and its durability will depend on the quality of posts used. If possible, live posts of

willow, popular and other should be used (8 – 10 cm in diameter). Thicker branches used as

vertical posts driven into the soil to about 50 cm– 100 cm (1/3 to half of the post length) depth

and spaced about 30 to 50 cm apart. The posts will have a length of 1 – 2 m. The space between

the posts will depend upon the height of the check-dam. The higher the dam, the closer will be the

distance between the posts.



ii. Double row brushwood check-dam

This type of brushwood check-dam is suited where the flow of runoff is less than 1 m3/sec. The

construction of the dam starts with an excavation inthe floor and into the sides of the gully to a

depth of 0.3 – 0.5 m. Two rows of posts, 5 -10 cm in diameter and 1 - 2 m in length placed into

the holes, across the floor of the gully to a depth of 0.5 – 0.6 m. The spacing between the posts is

0.5 m. The height of the posts in the center should not exceed the height of the spillway otherwise

the flow will be blocked and water may be forced to move to the gully sides

c. Loose stone check-dam

Loose stone check-dam is a structure made of relatively small rocks and placed across the gully

or small stream, which reduces the velocity of runoff and prevents the deepening and widening of

the gully. The Sediment accumulated behind a check-dam used for plantation of crops or

trees/shrubs, grasses and thus provide additional income tothe farmer. This commonly used to

check gullies on highly eroded grazing and cultivated lands and hillsides.A loose stone check-

dam should full fill the following minimum standards.

The Bottom key and foundation is 0.5 m deep, side key 0.5 – 1 m per side ,height: 1 – 1.5 m

excluding the foundation, mostly 1 m is suffice to avoid failures ,base width: 1 m – 3. 5 m. The

spillway (trapezoidal/parabolic): 0.25 – 0.5 m permissible depth and 0.25 m free board; and width

0.5 – 1.2 m, apron length should be at least 1.5 times of the effective height of the check-dam and

as wide as the gully bed and the apron placed in an excavation of about 0.3 – 0.5 m to ensure

stability and prevent wash away. A sill of about 15 cm constructed on the lower end of the apron.

d. Gabion check-dam

Gabions are rectangular boxes of varying sizes and are mostly made of galvanized steel wire

woven into mesh. The boxes tied together with wire and then field with either stone or soil

material and placed as building blocks. Large and smallstones filled with in the gabion to protect

from heavy runoff washed away and correctly installed.

The main advantages of gabions are tough and long lasting that the wire has been well

galvanized. Furthermore, they are somewhat flexible and installed where the surface is uneven.

They used to stabilize gully sides, gully heads, roadside embankments, riverbanks and even

landslips. This should integrate with biological measures to restore and play a great role for

rehabilitation of the gully.

Gabion check-dams undermined or bypassed round the side due to incorrect installation or

unstable soils. Common problems are failure to embed the gabions to a sufficient depth in the



floor of the gully and failure to insert to a sufficient distance in to the gully banks. Once in placed

and properly anchored, gabion check-dam can resist even strong flood sand last for a long time.

Gabion check-dams built usually not high than1.5 m spillway height in the first year. After

sediments deposited behind the structure, it is possible to raise the spillway height by adding

additional gabion boxes. Nowadays, different sized gabions are available commercially in the

country.

Table 36: Different sizes of gabions (Length x Width x Height) and wire requirement for each

No Gabion Size

(m)

2.5 mm wire

(kg)

3.5mm wire

(kg)

Tying wire

(kg)

Share of each size during

construction (%)

1 2x1x1 12.0 2.3 0.6 60

2 2x1x0.5 8.5 1.7 0.5 20

3 1x1x1 7.0 1.5 0.4 15

4 1x1x0.5 3.4 0.9 0.3 5

(Source: Lakew & Belayneh, 2012)

Design and construction specification of a gabion check-dam. The foundation depth (key trench)

should not be less than 50 cm. The foundation width is 1m and the structure plugged one meter to

each side of the gully wall /abutment/ right up to the height of the dam. Construct apron from

downstream side of the structure with a foundation of 30cm from a dry stone, with a width of 1.5

times the reservoir level. For the spillway, the general design criteria given for loose stone check-

dam is applicable here. It should be adequate to allow the peak flows, without overtopping the

dam. An apron of stone/similar gabion box about 1.5 m times the height of the spillway is

necessary. General considerations for the apron are the same as for the loose stone check dam.

6.2.2 Biological Soil and Water Conservation Measures

Biological soil conservation has economic and ecological linkages in the way of providing

adequate groundcover and narrowing the gap between population pressure and carrying capacity

of the land. The ground cover or vegetation cover maximized by improved soil conditions and

effective management of rainfall and run-off. If the physical, chemical and biological properties

of the soil are improved pastureland and forest productivity and the environment also changed.

The effective control of soil erosion and improvement of agricultural productivity through

biological soil conservation techniques determines the linkage of strong economic and ecology in

biological soil conservation. Currently there are little efforts of plantation of different plant

species as biological soil conservation measures within the sub basin by community participation.

Therefore, multipurpose trees integrated, as biological conservation measures mustpropose. The

biological conservation measures should be thedrought resistance species, forageand fruit

trees.Even though the importance of these species is not widely understood by the community

great extension should be transferred and done in the sub basin about their importance and



functional. Therefore, as a component of biological interventions, in order to get seedlings and

seeds of the species nursery establishment is the main thing in the sub basin. In the sub basin,

nursery sites notwell establishedso that it mustestablish in the sub basin in order to stabilize

physical conservation structures with biological measures. The nursery should be good

management and adequate budget for runningcost.

Every project component proposed in the sub basin has direct linkages with other sectors. The

plantation of different species for soil bund stabilization is linked with animal husbandry and used

for animal feed through cut and carries system; it is also linked with the agricultural study as it

contributes to soil fertility improvement and increased access to water resources for more

production. The physical structures to undertaken on the uplands reduce the sediment deposition

and flooding on the down streams of the watershed, which is a severe problem and increase

ground water recharge in the low land areas. Fruit trees have a significant role as a soil and water

conservation interventions in income generating and intensification of land besides conserving the

soil.

I. Grass strip

It is a strip of grass laid out on cultivated land along the contour. Usually, grass strips are about 1

meter wide and spaced at 1-2meter vertical interval .they are mainly used to replace physical

structures on soil with good infiltration on gentle slopes. The sub basin suitable for grass strip is

about 245978.6ha and covers 19.28%. This structure is practice easily with in gentle slopes and

almost flat areas.Cattle excluded from these measures all the yearlong to provide for sufficient

length of the grasses to slow runoff and retain soil sediment. Grass strips planted along the

contour or cut off drain. Grass should be perennial and resistance, compete with and suppress

weeds, provide good ground cover, protect the soil from erosion and conserve the soil moisture.

Planting carried out at the onset of rainfall, when the soil is not too wet and dry. Early planting

gives the vegetation an opportunity of getting more rain and better establishment.

Table 37: Spacing for grass strip down a slope (RELMA and MOA, 2005)

No Slope (%) Spacing (m)

1 <3 >33

2 3-5 20-33

3 5-8 13-20

4 8-11 10-13

5 11-15 7-10

II. Planting on physical structures

Planting of crops, grasses, shrubs or trees in different combinations for stabilization of physical



structure. It should combine with other purposes for the maximization of the use of the woody

plants grown. This is suitable in all land uses

Technology description: close spacing, use seedlings instead of direct seeding, nitrogen fixing

trees for forage purposes, single row planting preferred, side pruning of trees after 1-2 years and

root pruning may be necessary to avoid competition with crops

III. Crop Rotation and Inter-Cropping

Crop rotation with intervals of cereals and legumes applied to improve soil fertility, which

enhance biomass production and maximize land cover. These are very important for halting

splash erosion and controlling soil moving with surface runoff. Crop types for both crop rotation

and inter-cropping carefully selected to maximize soil and water conservation as well as

economic value. This applied in crop cultivation of both altitudes and in all slope ranges.

Cover crops and green manure:Cover crops grown as soil conservation measures during the off-

seasons. The plants, in most cases, grown on the surplus moisture after the previous crop

harvested. Such crops grown, ploughed, and mixed with the soil in their young age as green

manure. Crops used for this purpose must be legumes like chickpeas, lintels and Sesbania tree

species. This also used mainly in medium altitude farmlands.

IV. Hedgerows

This activity already partially practiced in the sub basin along some field boundaries and

homesteads. However, it should expanded with the plant species and planting designs

improvement in order to meet soil conservation functions; livestock feed and fodder production

and fuel and construction wood production. In relation to these, hedgerows designed, as much as

possible, on contour lines along and between field crops and homestead. Plant, shrub and grass

species planted should be with multipurpose quality and fast growing. The species must have high

palatable biomass for livestock feed and forage; enriching ability of soil nutrients; high yield of

food, fuel and construction wood; quality for soil and water conservation but not aggressively

compete or suppress the field crops; and social acceptance in the area. Under growing of grass

and bushy shrub, species with these hedgerows would be very important to control the movement

of soil particles. In addition, a meter wide grass along the hedgerows would supplement grazing

to animals given special attention like lactating cows, calves and draught animals and more

control of soil movement.

V. Agroforestry Practice

Agroforestry defined as all practices that involves a close association of trees and shrubs with

crops,animals and /or pastures. Agroforestry may involve a combination of practices in the same

place at the same time (intercropping or related practices) or practices in the same place but at



different time (rotational practice)

VI. Dispersed trees in the farm

Trees may be grown on farmers‟ fields while crop grown in the under storey. The trees may be

dispersed widely, either spaced systematically in grid or scattered at random. The practice of

raising trees dispersed on crop land may be used based on the protection and management of

selected trees on the site. Spacing is determined by the size and requirement of the trees and in

order to fit trees in to the crop land in a way of that minimizes interference with crop cultivation

and that makes the best use of any positive effects of the trees on crops.

VII. Boundary and border planting

Demarcation of areas between different land owners or land uses, different from live fences in

objective and border plants are usually allowed to grow taller while living fences are trimmed

regularly

VIII. Protection and Stabilization of water way and gullies

Permanent vegetation particularly trees and shrubs can play major role in stabilizing artificial

waterways and gullies as well as natural stream banks. Woody vegetation helps decrease water

velocity along the channel edges and protects exposed soil, gravel or rocks from the erosive

forces of flowing water. In smaller channels and even in extremely steep ones such as gullies,

trees shrubs and grasses can reduce flow velocity across the entire channel.

IX. Soil and water conservation measures for grasslands

Grass land is a land use type where the dominant species are grasses and included cultivated land

that was or will have to be the abandoned from cultivation and change into grass land. The system

should practice controlled grazing, rational grazing and cut carry to protect from land

degradation.

Controlled grazing: controlling the number and types of livestock that graze a pasture

prevent over grazing and avoids waste feeding.

Rational grazing is a form of controlled grazing and involves dividing pasture land into

several paddocks and allowing livestock to graze each in turn.

Cut and carry involves keeping animals in a shed or paddock and bringing fodder to them

rather than allowing them to graze outside. It is also called zero grazing or stall-feeding.

X. Area Closure

Area closure is suitable for degraded areas in most agro-climatic parts of the sub basin. It

commonly practiced inEthiopia with different levels of performance. Best-closed areas found

when directly managed by the communityand groups of interested farmers. Based on the analysis



the sub basin suitable for area closure is about 354201.9ha and covers 27.76%. Area closure

increases the productivity of degraded and moisture stressed areas and combined with different

soil and moisture conservation measures.Area closure restores sufficient productivity for the

growth of multipurpose trees,grass and specific cash crops. Area closure protects downstream

fertile fields from flood and erosion and contributes torecharge aquifers. When properly managed

area closure can provide significant income to poorest households.

Therefore, the first duty of the natural resource managers and the political leaders especially and all

the citizens as a whole should be responsible in all conservation interventions and could create

awareness one to the other. Natural resources conservation and management is not left for only for

the conservationist, it the duty of all citizens. Hence, all sectorial offices should cooperate and

givesupport for the facilitation of natural resources management. The area closure will benefit the

surrounding community in providing adequate fuel wood and construction materials. It directly

linked with job creation for the rural youth and as well as solving the problem of landlessness in the

rural areas.



:

7. CONCLUSION AND RECOMMENDATION

7.1 Conclusion

Land degradation (water erosion) is serious problem in the sub basin due to strong

linked with livelihoods of the community like over grazing and deforestation due

to population pressure; resulted high amount of soil is erosion and expansion of

desertification.

Water erosion and flood are the other serious problem in the sub basin.

Watershed based land use planning work is not well established (developed) in the

sub basin.

Lake Tana seriously affected with sediment load and the amount of water content

and depth of the Lake decrease year to year.

Areas >30% slopes are ploughed by the local people and this increase amount of

soil degradation towards Lake Tana.

Physical soil and water conservation structures with in the sub basin constructed in

large amount but the quality is still under problem.

7.2 Recommendation

To solve the problems of soil degradation in the sub basin great extension and new

technology application should practice.

To solve the problem of watershed based land use planning in the sub basin at all

levels (from kebele to regional) watershed principles, ways of management and its

importance should be cleared and trained.

As the other problems,water erosion is a serious problem in the sub basin so that

physical and biological soil and water conservation structures fully practice in the

sub basin and further farmer extension should done for the severity and effects of

water erosion.

The flood comes from upper catchment of the sub basin if it is possible treated by

different types soil and water conservation structures and the excess amount of

flood should be protected by constructing gabion check dam near the riverside in

order to protect from increasing of riversides width and over topping.

Physical and biological soil and water conservation structures in the sub basin



should be well established with standards, actual norms and maintained

properly.Finally, as an introduction of zero grazing scaling up must practice.

It is from this viewpoint that the government is taking different actions to reverse

the problems. During this study the severity of the problems are identified which

indicates site-specific interventions. For this purpose the involvement and

consultation of the community for the implementation and sustainability of the

interventions is very decisive. The other important point considered is building the

capacity of the government staffs who are supposed to implement the projects at

all level. The Woredaagricultural office is the immediate responsible for

implementation of the project and thus strengthening of the office in all aspect is

very crucial. The Woreda staffs also should get adequate training on the subject

matter before the commencement of the project in their respective working area.



8. REFERENCES

1. Acres and Shawel, 1995.Watershed management plan of Koga irrigation project feasibility

Study Report.

2. Black, 2001. Conservation of Water and Related land Resource 3rdedition pp .403.

3. Foster, G.R., 1982. Modelling the erosion processes. In: C.T. Haan (Editor), Hydrologic

Modelling of Small Watersheds. ASAE Monograph, pp. 297-380.

4. IFAD/EPLAUA, 2007.Baseline Information of Community-Based Integrated Natural

Resources Management Project in Lake Tana Sub-Basin.

5. Lu, X. and Higgitt, D.L. 2001. Sediment delivery to the Three Gorges. 2: local response.

Geomorphology, 41: 157-169.

6. McDonald and Partners in collaboration with Institute of Hydrology. 1991. Hydrometry

Project Somalia. Final Report, Phase 3.

7. McDonald and Partners. McDonald and Partners in collaboration with Institute of Hydrology.

1991. Hydrometry Project – Somalia. Final Report, Phase 3

8. MoARD, 2005. Community Based Participatory Watershed Development. Volume 1 and 2

.Addis Ababa, Ethiopia.

9. MORGAN, R.P.C. 1995.Soil Erosion and Conservation.Edinburgh: Addison-Wesley

Longman.pp. 198

10. MORGAN, R.P.C. 1994. Soil Erosion and Conservation. Silsoe College, Cranfield

University. MORGAN, R.P.C. 1974.Estimating regional variation in soil erosion

hazard in Peninsular, Malaysia. Malayan Nature Journal 28: 94-106.

11. Norman W. Hudson, 1987.Soil and water conservation in semi-arid areas. Food and

Agriculture Organization of the United Nations Rome.

12. NYSSEN, J.1997. Soil erosion in Tigray Highlands (Ethiopia).IIsOIL loss estimation.Geo-Eco-

Trop.,21(1) pp 27-49

13. Poesen, J., Nachtergaele, J., Verstraeten, G. and Valentin, C., 2003. Gully erosion and

environmental change: Importance and research needs. Catena, 50: 91-113

14. Saavedra, C. 2005. Estimating spatial patterns of soil erosion and deposition in the Andean

region using geo-information techniques. A case study in Cochabamba, Bolivia. PhD Thesis,

ITC, Enschede

15. TCS, 2013. Baseline Survey of Community-Based Integrated Natural Resources Management

Project in Lake Tana Sub-Basin



16. Thornes, J.B. 1990. Vegetation and Erosion: Processes and Environments. Wiley, ChicHester,

London, UKWischmeier, W.H., Smith, D. D., 1978. Predicting Rainfall Erosion Losses.

Agricultural Handbook 537. USDA, Washington, DC, USA.

17. WWDSE/TAHAL, 2008.Watershed Management final feasibility Study Report Design of Rib

Dam in Lake Tana Sub-Basin Project.



9. APPENDICES

Appendix I. RUSLE Estimation Parameter

Table 38: FAO soil unit & their corresponding K values

FAO soil unit K- value FAO soil unit K- value FAO soil unit K- value FAO soil unit K- value

Eutric Fluvisol 0.15 Luvic Phaeozem 0.1 Ranker 0.1 Eutric planosol 0.2

Calcaric Fluvisol 0.1 Gleyic Phyaeozem 0.1 Haplic Phaeozem 0.1 Dystric Planosol 0.2

Dystric Fluvisol 0.1 Eutric Cambisols 0.15 Calcaric Phaeozem 0.1 Mollic Planosol 0.15

Eutric Gleysol 0.15 Dystric Cambisols 0.15 Humic Planosol 0.15 Cacic Xerosol 0.2

Calcaric Gleysol 0.1 Humic Cambisols 0.1 Solodic Planosol 0.2 Gypsic Xerosol 0.2

Dystric Gleysol 0.15 Gleyic Cambisols 0.15 Ochric Andosol 0.15 Luvic Xerosol 0.2

Mollic Gleysol 0.1 Calcaric Cambisols 0.15 Molic Andosol 0.1 Orthic Acrisol 0.15

Humic Gleysol 0.1 Chromic Cambisols 0.15 Humic Andosol 0.1 FerricAcrisol 0.15

Plinthic Gleysol 0.15 Vertic Cambisols 0.2 Vertic Andosol 0.15 HumicAcrisol 0.1

Eutric Regosol 0.15 Ferallic Cambisols 0.15 Pellic Vertisol 0.2 Plinthic Acrisol 0.2

Calcaric Regosol 0.1 Orthic Luvisol 0.15 Chromic Vertisol 0.2 Gleyic Acrisol 0.15

Dystric Regosol 0.15 Chromic Luvisol 0.15 Orthic solonchak 0.15 Eutric Nitosol 0.15

Lithosol 0.1 Calcic Luvisol 0.15 Molic solonchak 0.1 Dystric Nitosol 0.15

Cambic Arinosol 0.1 Vertic Luvisol 0.2 Takyric solonchak 0.2 Humic Nitosol 0.1

Luvic Arinosol 0.1 Ferralic Luvisol 0.15 Gleyic solonchak 0.15 Orthic Ferralosol 0.15

Feralic Arinosol 0.1 Albic Luvisol 0.2 Orthic solonetz 0.2 Xanthic Ferralosol 0.15

Albic Arinosol 0.1 Plinthic Luvisol 0.2 Mollic solonetz 0.15 Rhodic Ferralosol 0.15

Rendzina 0.1 Gleyic Luvisol 0.15 Gleyic solonetz 0.2 Humic Ferralosol 0.1

Source:Reconnaissance Physical Land Evaluation in Ethiopia. (FAO, 1989)

Table 39: Major soil unit, soil color and K- Values

No Major soil Soil color SCRP estimates of K-value

1 Eutric Fluvisols Mostly brown but variable 0.2

2 Eutric Vertisols Dark grey or Black 0.15

3 Eutric Cambisol Brown or Dark brown 0.2

4 Eutric Leptosols Brown to yellowish brown 0.2

5 Haplic Alisols Reddish brown 0.25

6 Haplic Luvisols Brown /Reddish brown 0.2

7 Haplic Nitosols Reddish brown 0.25

8 Chromic Luvisol Brown /Reddish brown 0.2

9 Lithic Leptosols Brown to yellowish brown 0.2

10 Eutric Regosols Brown 0.2



Table 40: K value based on the soil texture and organic matter content

SN Soil Type Textural class

K value

Average <2(%) >2(%)

1 Cambic Arenosols Sand 0.02 0.03 0.01

2 Eutric Cambisols Sandy loam, clay, clay loam 0.13 0.14 0.12

3 Eutric Leptosols Clay loam 0.3 0.33 0.28

4 Rendacize Leptosols Sandy loam, Loam, clay loam 0.3 0.33 0.28

5 Vertic Cambisols Clay 0.22 0.24 0.21

6 Rock surface (Regosols) Coarse Sandy 0.07 - 0.07

(Source: Adapted from Robert and Hilborn, 2000)

Table 41: Soil Erodibility Factor (K) (Schwab et al., 1981)

Textural Class

OM (%)

Textural Class

OM (%)

0.5 2 0.5 2

Fine sand 0.16 0.14 Very fine sandy loam 0.47 0.41

Very fine sand 0.42 0.36 Silt loam 0.48 0.42

Loamy sand 0.12 0.10 Clay loam 0.28 0.25

Loamy very fine sand 0.44 0.38 Silt clay loam 0.37 0.32

Sandy loam 0.27 0.24 Silt clay 0.25 0.23

Table 42: Crop Factor and land use land cover

No Land cover /use class Source C_factor

1 Forest Hurni, 1985 0.01

2 Shrub land CGIP,1996 0.02

3 Grass Land CGIP,1996 0.01

4 Dense grass Hurni, 1985 0.01

5 Degraded grass Hurni, 1985 0.05

6 Crop land/ wooded crop land CGIP,1996 0.15

7 Crop land, Teff as a main crop Hurni, 1985 0.25

8 Crop land, cereals, pulses Hurni, 1985 0.15

9 Crop land: wheat, barely CGIP,1996 0.15

10 Crop land: sorghum, maize Hurni, 1985 0.10

11 Afro-alpine BCEOM,1998 0.01

12 Open scrub land CGIP,1996 0.06

13 Bush land BCEOM,1998 0.1

14 Bare land BCEOM,1998 0.6

Table 43: Land capability classes andSWC Options at different land cover

Land

class

unit

Major

limiting

factor

Cultivated land Grazing land Forest land

I Nil Intensive cultivation

+maintaining good

vegetation cover +water

ways +water harvesting

in moisture stress areas

Convert to

cultivated land

Grass land

Improvement

Converted to

cultivated

Converted to

agroforestry

II 3-8% Contour cropping

Strip cropping

Grass strip

Convert to

cultivated land

Grass land

Converted to

cultivated

Converted to



Alley cropping +

Water ways,

cutoff drains

Improvement agroforestry

III 8-15% Grass strip

Alley cropping

Combination of

grass strip and

bunds

Soil or stone

bunds

Fanay Juu+

waterways ,cutoff

drains

Moisture

conservation in

arid & semi-arid

areas

Convert to

cultivated land

Grass land

Improvement

Converted to

agro

silvipasture

+ cutoff drains

Converted to

cultivated

Converted to

agroforestry+

strip plantation

IV 15-30% Combination of

grass strip and

bunds

Alley cropping

Soil or stone

bunds

Fanay Juu

Bench terraces

Moisture

conservation in

arid & semi-arid

areas

Convert to

cultivated land

Grass land

improvement

Converted to

agro

silvipasture +

cutoff drains

and

waterways

Establish

silvipasture

Enrichment

planation

Fuel wood

planation+

micro basin

Vi 30-50% Establish

perennial crops

Converted to

grass land or

forest land

Bench terrace for

annual crops

+waterways

Grass land

improvement

Controlled

grazing

Converted to

agro

silvipasture +

cutoff drains

Established

silvipasture

Enrichment

plantation

Fuel wood

planation +

micro basins

VII >50% Convert to forest

land

Convert to

silvipasture land

Hillside terrace

for annual crops

Convert to

forest land

Convert to

silvipasture

land

Control

Fuel wood

planation

Tree planation

Tree planation

for catchment

protection



+cutoff drain grazing +cut

and carry

+pitting or

micro basin

VIII >50% Area closure

Convert to forest

land( catchment

protection )

Cut and carry

Area closure

Convert to

forest land(

catchment

protection

Protection of

natural forest

,if forest exist

Area closure

encourage

wildlife

V Swaps,

river beds

not applicable temporary

grazing

control

grazing

encourage

wildlife

Appendix II Secondary Data of Watershed Management

1. Location

1. 1 Zone Name...................................

1.2 Woreda Name..................................

1.3 Kebele............................................

2. Gully Assessment

No Size of gully

(depth m)

Amount by cover

Grazing land Cultivated Others Total

Length Width Length Width Length Width Length Width

1 < 1m

2 1-5m

3 >5m

3. SWC Achievement

SN Measures Unit

Achievements(E.C.)

Total

2001 2002 2003 2004 2005

1 Watershed Approach

1.1 Watershed delineation and study No

1.2 Watershed development No

2 Physical SWC Measures

2.1 Bund Km/ha

2.2 Soill Bund Km/ha

2.3 Stone Faced Soil Bund Km/ha

2.4 Stone bund Km/ha

2.5 Hillside Terrace Km/ha

3 Flood Control

3.1 Cut Of Drains Km/ m3

3.2 Water Ways Km/ m3

4 Water conservation structures

4.1 Micro basin No



4.2 Eyebrow basin No

4.3 Trench No

4.4 Percolation pit No

5 Gully control

5.1 Stone check dam km /m3

5.2 Gabion check dam km /m3

5.3 Brush Wood Check Dams Km /m3

5.4 Sand suck Check Dams Km/m3

6 Bio physical & Biological SWC

6.1 Plantation On Bunds Ha/km

6.2 Area Closure Ha

6.3 Gully Plantation Ha

6.4 Grass strip Ha

The Federal Democratic Republic of Ethiopia Amhara ... · Amhara region.Tana sub basin categorized under four major watersheds, namely Megech, Rib, Gumara and Gilgel Abay.The major

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