Updating the hydrology of the Baro-Akobo-Sobat basinnbdf.nilebasin.org/sites/default/files/Jonker et al BAS NBDF 2017_2_.… · • Integrated Water Resources Management & Development

Updating the hydrology of the Baro-Akobo-Sobat basin

V Jonker (Aurecon), M Botha (Aurecon), S Crerar (BRL), A Mersha (ENTRO),

JE Muso (ENTRO), F Negash, (ENTRO), N Sicard (BRL)

Background

• In 2015 ENTRO commissioned the Baro-Akobo-SobatMultipurpose Water Resources Development Study Project

• Purpose: To promote socio-economic development, regional cooperation and peace through sub-basin wide cooperation in integrated water resources development and management

• Project team: BRL (lead), Aurecon & Yerer• Project currently being completed

Project objectives

• To develop an Integrated Water Resources Management and Development Plan for the Baro-Akobo-Sobat Basin

• Based on a Strategic Social and Environmental Assessment (SSEA) - allows early/upstream identification/integration of environmental and social considerations into development of IWRMDP

• Main deliverables:• Strategic Social and Environmental Assessment • Integrated Water Resources Management & Development Plan• Water resources model• Spatial database• Short term projects - Feasibility studies (x3)• Medium and long-term projects – TORs Feasibility studies (x3)

The Baro-Akobo-Sobat Basin

• Shared river basin• Very little development• Vulnerability to floods / droughts• Environmentally sensitive areas

• Wetlands / marshes• Forest ecosystems• Antelope Migration

• Water dependent livelihoods• Crop cultivation• Pastoral farming

• Potential• Hydropower• Irrigation• Tourism

• Lack of information• Complex hydrology• Conflicts – natural resources

Physiography: Topography, Rivers, Sub-basins

Climate: Rainfall

399 masl

610 masl

1740 masl

421 masl

Climate: Evaporation

Climate: Temperature

Droughts

Climate: Droughts

Surface water modelling

Data compilation and preparation

Calibrate/Validate RR model

Simulate long-term flow sequences

Configure/Validate Systems model

Scenario Simulations

Model output to define Baseline and

inform Scenario evaluation

Objectives Quantify available water in space

and time

Assess hydrological and related social, environmental and economic impacts and benefits of interventions

Refinements Subcatchment delineation

Drainage network

Review / Improve hydromet data

Rainfall-Runoff modelling

Floodplain dynamics

Simulation period

Rainfall data Data sources

• NBI database of patched monthly rainfall values across Nile Basin (1904 – 2011)

• Daily gridded rainfall - Swedish Meteorological and Hydrological Institute (1951 - 2005)

• Monthly gridded rainfall - Climatic Research Unit Univ. East Anglia (1901 - 2014)

Rainfall data - chronogramme

Hydrological Data83 gauging stations existed in the Baro-Akobo-

Sobat Basin historically

Data sources

• Nile Basin Encyclopedia

• Ethiopian Master Plan Reports

• Nile Basin Research programme

• Nile Basin Initiative

• ENTRO databases

• Ethiopian Ministry of Water, Irrigation and Electricity

• Previous studies

FLOW STATION NAME SOURCE

Alwero at Abobo EMP

Baro at Burebeiy NBRP

Baro at Gambela NBI

Baro at Gambela NBRP

Baro at Gambella EMP

Baro at Itang NBI

Baro at Kella NP

Baro at Masha NP

BirBir at Yubdo NBI

Geba at Suppi NBI

Pibor at Pibor Post NBE

Pibor at Pibor Post NBI

Pibor upstream of Khor Gila mouth NBE

Pibor upstream of Khor Gila mouth NBI

Sobat at its mouth into White Nile (at Hillet Doleib) NBE

Sobat at Nasser NBE

Sor at Metu EMP

Sor at Metu EMWE

Abu Tong cut at its mouth into White Nile NBE-NBI

Adura at its head downstream of Baro-Adura bifurcation NBE-NBI

Adura downstream of Khor Makwai mouth NBE-NBI

Agwei at its mouth into Pibor NBE-NBI

Akobo at its mouth into Pibor NBE-NBI

Assua at its mouth into Bahr el Jebel NBE-NBI

Baro at its mouth into Sobat NBE-NBI

Baro downstream of Baro-Adura bifurcation NBE-NBI

Baro downstream of Baro-Adura junction NBE-NBI

Baro downstream of Khor Jakau mouth NBE-NBI

Baro downstream of Khor Machar head NBE-NBI

Baro downstream of Khor Makeir head NBE-NBI

Baro upstream of Baro-Adura bifurcation NBE-NBI

Baro upstream of Baro-Adura junction NBE-NBI

Baro upstream of Khor Jakau mouth NBE-NBI

Baro upstream of Khor Makwai head NBE-NBI

Khor 18 kms upstream of Machar head at head NBE-NBI

Khor 18.5 kms upstream of Machar head at head NBE-NBI

Khor 3.5 kms upstream of Machar head at head NBE-NBI

Khor 4.3 kms downstream of Machar head at head NBE-NBI

Khor 4.8 kms upstreamof Machar head at head NBE-NBI

Khor 6.5 kms upstream of Khor Jakau mouth at its head NBE-NBI

Khor Atar at its tail into White Nile NBE-NBI

Khor Barakwich at its mouth into Baro, 7 kms downstream of Machar head NBE-NBI

Khor Fullus at its mouth into Sobat NBE-NBI

Khor Geni at its mouth into Pibor NBE-NBI

Khor Gila at its mouth into Pibor NBE-NBI

Khor Jakau at its mouth into Baro NBE-NBI

Khor Lolle at its mouth into White Nile NBE-NBI

Khor Macap at its mouth into Pibor NBE-NBI

Khor Machar at its head (offtake from Baro) NBE-NBI

Khor Makeir at its head NBE-NBI

Khor Makwai at its mouth into Adura NBE-NBI

Khor Mokwai at its mouth into Pibor NBE-NBI

Khor Nyanding at its mouth into Sobat NBE-NBI

Khor Twalor at its mouth into Sobat NBE-NBI

Khor Wakau at its mouth into Sobat NBE-NBI

Pibor at its mouth into Sobat NBE-NBI

Pibor downstream of Akobo mouth NBE-NBI

Pibor downstream of Khor Gila mouth NBE-NBI

Pibor downstream of Khor Makwai mouth NBE-NBI

Pibor upstream of Akobo mouth NBE-NBI

Pibor upstream of Khor Makwai mouth NBE-NBI

Sobat at 2 kms downstream of Nyandig mouth NBE-NBI

Sobat at its head NBE-NBI

Sobat downstream of Khor Twalar mouth NBE-NBI

Sobat upstream of Khor Twalar mouth NBE-NBI

White Nile At Kosti NBE-NBI

White Nile at Malakal NBE-NBI

White Nile at Melut NBE-NBI

White Nile at Mogren (Khartoum) NBE-NBI

White Nile at Renk NBE-NBI

White Nile downstream of Jebel Aulia Dam NBE-NBI

White Nile downstream of Lake No NBE-NBI

White Nile upstream of Maya Berboi head NBE-NBI

White Nile upstream of Maya Sinyora Gauge NBE-NBI

LEGEND

All Months Data Available

6 Months Data Available

1 Months Data Available

No Data Available

1980-89 1990-99 2000-09 2010-2015

To be

used

for c

alibr

ation

Auxil

iary S

tation

s

CALENDER YEAR

1903-09 1910-19 1920-29 1930-39 1940-49 1950-59 1960-69 1970-79

Flow data - chronogramme

NAM Model calibration

Observed Simulated Difference

Mean Annual Runoff

(million m3/a)

13 091 13 434 +2.6%

Standard Deviation of

Monthly Flows (m3/s)

386 374 -3.0%

R2 0.92

Baro River @ Gambella

Observed Simulated Difference

Mean Annual Runoff

(million m3/a)

577 599 3.8%

Standard Deviation of

Monthly Flows (m3/s)

14 16 15.3%

R2 0.85

Alwero River @ Abobo

Model configuration and conceptualisation

African Wetlands GIEMS D15GIEMS D3

TTI

Flood progression - ADD

Flood progression: Aug to Dec 2007

Model validation -Floodplain

seasonality and extent

Wetland Max area (km2)

Min area (km2)

Avg. area (km2)

Machar Marshes

7800 400 3000

Sobat 4400 0 540

Gambellaplains

6800 0 2400

Gwom / Agwei

8000 0 4200

Badigeru/Veveno/ Lotilla

3600 0 400

Kangen 320 0 100

Floodplain/Wetlands:

Maximum modelled inundation surface areas

Machar Marshes

Kangen

Gwom/

AgweiVeveno/

Lotilla/

Badigeru

Sobat

Gambella

Plains

Model Validation - observed flows

Sobat River @ Hillet DoleibBaro River u/s Pibor confluence

Surface Water Baseline:Simulated stream flow (1905 - 2014)

Water Balance (Baseline)Total runoff generated: 26 BCM/aOutflow to White Nile: 13 BCM/a

Groundwater Yield

Sediment yield

• High Sediment Loads -Major issue

• Causes• Erosion, Steep slopes, High

intensity rainfall, Poor farming practices, Deforestation, Trampling (cattle)

Final scenario evaluation

Scenario 1: “Precautionary Principle” - no encroachment into environmentally sensitive areas. Irrigation dam storage volumes reduced. All potential hydropower dams except Tams Dam and Birbir Dam.

Scenario 2: An extension of the Precautionary Principle case, similar to Scenario 1, except that Tams Dam and Birbir Dam are included.

Scenario 4a: Full-development case, with Tams Dam operated to maximise hydropower production.

Scenario 4b: Full-development case, with Tams Dam operated to optimise irrigation and flood control.

Scenario 3a: Compromise case, similar to Scenario 2, but with environmental water releases imposed on all dams.

Scenario 3b: Compromise case, similar to Scenario 4a, but with environmental water releases imposed on all dams.

Defining the development space:Multidimensional analysis

0

1000

2000

3000

4000

5000

6000

7000

1 2 3 4 5 6 7 8 9 10 11 12

Are

a (k

m² )

Month

Seasonality of maximum wetland area - Machar

Scenario 0

Scenario 1

Scenario 2A

Scenario 2B

Scenario 3

Scenario 4

Typical water resources model based outputs

Wetlands / Floodplains

Water balance

Typical water resources model based outputs

0.00

0.05

0.10

0.15

0.20

0.25

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Ave

rage

Mo

nth

ly F

low

(BC

M)

Month

4a

Deficit

Used Water

Large scale irrigation

Flood risk

Water availability

Financial / Economic

Projects included in scenario analysis

Scenario evaluation: metrics

BAS IWRMDP

Thank you!