Hydrology and Environmental Perspective of Bagmati River Basin

Hydrology and Environmental Perspective of Bagmati River basin

ByMadhav Narayan Shrestha, Ph.DEmail: [email protected]

1. Introduction: Bagmati river Basin

The Bagmati river basin is a medium sized river basin with a catchment area of 3700 km 2 at the Nepal India Border. It extends between 20042' to 27050' north latitude and 85002' to 85058' east longitude. It originates from the Shivapuri hills in the Mahabharata range of mountains and flows down south into the Terai plains before crossing the Indo Nepal border. Along its course the river passes through eight districts, namely, Kathmandu Lalitpur, Bhaktapur, Kavrepalanchowk, Makwanpur, Sindhuli, Rautahat and Sarlahi. The major tributaries of Bagmati River are Manohara, Bishnumati, Kulekhani, Kokhajor, Marin, Chandi, Jhanjh and Manusmara. The Kathmandu valley comprises of 15% of the of the basin area in Nepal. The basin as a whole can be divided into three parts; the upper Bagmati basin comprising of the Kathmandu valley plus the upper Nakhkhu khola and Dakshinkali area, the Middle Bagmati basin comprising of the remainder of the basin in the hills including the Kulekhani khola; and the lower Bagmati basin comprising of the basin in the Terai, plus some tributaries which originate in the Shiwaliks The major tributaries of the Bagmati River are Nakkhu, Kulekhani, Kokhajor, Marin and Chandi River as shown in Fig.1. These tributaries are highly polluted. The municipal wastes and industrial effluents are directly discharged into the river that has made the water unusable for human and ecological needs along most of the course. In addition, the Kathmandu valley is facing a severe shortage of water due to the rapid urbanization leading to unsustainable water demand and generation of high volume of municipal and industrial effluents. The annual groundwater use for domestic and industrial purposes in the Valley is almost two times the annual rechargeable groundwater available.

The climatic condition of the Bagmati watershed is quite variable because of the intricate topography. Temperature generally decreases with elevation. It is low in winter. Rainfall occurs due to the southeast monsoon which lasts between the months of June through September. The humid monsoon air stream blowing from the Bay of Bengal is forced to rise as it meets the Himalaya. As a result, heavy rainfall occurs on some sections of the southern Himalayan slopes. Rainfall is also high along the Chure range. Regions close to the Indian border receive about 1500 mm rain in a year, while at the foot hills of Chure the annual rain fall reaches 2000 mm. On the northern side of the Chure the rainfall diminishes again. In the lee-ward side of the ranges, rainfall is reduced due to rain shadow effects. Orographic effect is pronounced and governs the pattern of rainfall.

Figure 1. Map of Bagmati river basin(Source: Preparation of Water – Induced Hazard Maps of Bagmati River Basin, 2005, DWIDP / SILT / ERMC / TECHDA)

The land use and land cover statistics derived from the 1992 topographical sheet exhibits that almost 50% of the Bagmati watershed is occupied by forests. Next to the forests are cultivated lands, which cover about 37% of the total area. The agricultural activities are confined mainly in the Terai, and in the river valleys and the gentle slopes of the hilly region. Built up areas occupy an insignificant portion, less than 1%, of the total area. Metropolitan city of Kathmandu, sub metropolitan city of Lalitpur, and municipal cities of Bhaktapur, Madhyapur Thimi, and Kirtpur are the major built up areas in the watershed. There are thirty four meteorological stations within the vicinity of the catchment of Bagmati River. There are five significant sub basins. Description of sub basin is presented in Table 1. The basin area up to Pandhero Dovan (gauging station 589) is 2700 sq km and that of up to Indo-Nepal Border is 3700 sq km. Drainage hierarchy of the basin is presented in Table.2.

Table 1.Descriptions on various features of river network of Bagmati Basin Sub-basin Area (sq km) Drainage

Length (km)No. of

RaingaugesDrainage Density

Gauge Density

Basin-1 574.50 1909.434 18 3.324 1 in 31.92Basin-2 306.62 1473.258 3 4.805 1 in 102.21Basin-3 782.40 3402.050 1 4.348 1 in782.40Basin-4 1036.48 4126.244 0 3.981 -Basin-5 1000.00 1032.242 4 1.032 1 in 250.00

Total Area = 3,700 sq km

Table 2 Drainage hierarchy lengthS.N. Drainage Hierarchy Drainage Length (km)1 First Order 863.6922 Second Order 291.2343 Third Order 260.6784 Fourth Order 113.557

2. Water Withdraw for Industries

Water withdrawn from Bagmati River basin for industries is presented in Table3.

Table 3. Inventory of industries and quantity of water withdrawsTypes of Industry No Water Withdrawn Total

Quantity(l/d)

Remarks

Source Av. Rate (l/d)

Hotels→ 5 star + 4 star together 18 GW + Municipal 1,000,000 18,000,000

Hotels→ 3 star and below 205 GW + Municipal 500,000 102,500,000

Hospitals (Govt. + Pvt.) 37 GW + Municipal 300,000 11,100,000

Textiles, Carpets, etc. 85 GW + Municipal + Pvt. Supply

15,000 1,275,000

Dyeing Industries 10 GW 20,000 200,000

Beverages/ Soft Drinks 8 GW + Municipal 1,000,000 8,000,000

Breweries 3 GW + Municipal 500,000 1,500,000

Bricks/ Tiles/ Cement, etc. 27 GW 50,000 1,350,000

Hume pipe Industries 6 GW 50,000 300,000

Sugar Mill 3 GW 500,000 1,500,000

Food Processing 12 GW 100,000 1,200,000

Soap + Detergent + Chemicals 10 GW + Municipal 20,000 200,000

Laundry + Dry Cleaning 7 GW 100,000 700,000

Poultry + Animal Feed 30 Municipal 10,000 300,000

Meat +Meat Products 3 Municipal + Pvt. Supply

20,000 60,000

Slaughter House Many Municipal + Pvt. Supply

200,000 (LS) Not Regd.

Vehicle Servicing + Car Wash 25 (App.) GW + Municipal 10,000 250,000

Leather + Tanning Industries 4 GW 20,000 80,000

Pharmaceuticals 7 Municipal 10,000 70,000

Plastics and Wires 9 GW + Municipal 10,000 90,000

Iron and Steel 3 GW + Municipal 10,000 30,000

Others 6 GW + Municipal 10,000 60,000

(Source: FNCCI directory (2003-2005)

3. Analysis of Quality and Extent of Bagmati River Water

The water quality of Bagmati River is found of better quality as it moves down to Indian Boarder. The water quality of the tributaries of the Bagmati River outside the Kathmandu valley is found to be good and could be used for a variety of purposes. Water quality parameters observed on June 2007 along Bagmati River is presented in Table 4.

Table 4. Water quality parameters along the Bagmati RiverLocation pH Conductivity.

μmos/cm

TDS

mg/l

NH3

mg/l

NO3

mg/l

NO2

mg/l

DO

mg/l

COD

mg/l

BOD5

mg/l

Bagmati at Teku 7.23 1460 825 84.52 0.38 1.83 0 770 420

Bagmati at Khokana

7.48 874 468 45.64 0.32 0.67 1.90 390 195

Bagmati at d/s Kulekhani

7.88 662 345 23.18 05.03 1.29 6.90 37.5 16.50

Bagmati at U/S of the Kokhajor

7.26 246 154 4.73 0.11 0.17 6.30 82.50 34.00

Bagmati at D/S of the Chandi

8.36 446 254 0.07 ND (<0.02

ND (<0.05

)

6.30 8 1.40

Bagmati at Indo Nepal Border near Gaur

7.89 234 172 0.14 ND (<0.02

)

0.07 6 26 7

Dissolved Oxygen (DO) content in the river water was critical and was found to be extremely low within the Kathmandu Valley river stretch. As the river passes through the city core area the DO content declined to zero and no fresh water aquatic lives are expected to survive in such an environment. This condition is improved after mixing of the Kulekhani Khola with the Bagmati River. As the river traverses the DO content was found to increase and it no longer remained critical for aquatic lives. The pH of the Bagmati River water was found to be in the range of 7.23.-8.36. This indicates that the pH of the Bagmati River water is not critical and the water is not objectionable for variety of purposes including irrigation. Other water quality assessment parameters that include conductivity, total suspended solids, turbidity, ammonia nitrogen, nitrate nitrogen and nitrite nitrogen are found to be high in Bagmati River water within the Kathmandu Valley compared to river water outside the Valley. Ammonia (NH3) observation was found improving as it moves down.

4. Industrial Effluents and their Impacts in the Bagmati River

It is found that except few, no industry used to do treatment of its effluent before discharging it to the nearby watercourse and then ultimately to the Bagmati River. Only the industries inside the Hetaunda Industrial Estates used to do primary and secondary treatments of their wastes or effluents before discharging it to the nearly river namely Kara Khola which ultimately used to

Bagmati River. Other industries do only primary treatment. Physico-chemical and bacteriological test analysis shows that the quality of effluent from industries are far from safe and need necessary treatment before discharging it to the water course. The BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) of industrial effluent were found extremely high and at the same time the DO (Dissolved Oxygen) was comparatively very low.

5. Environmental Impacts due to Existing Structures

Existing structures within 200m buffer width of the Bagmati River in the Kathmandu Valley are listed below and its environmental impact on the river is provided in Table 5,6,7,and 8.

a. Ghats Name of the Ghat Location

Bhara Karneshwor Mahadav ghat - Nayapati VDC-1, KMCKagbani ghat - Border of Gagalfidi and Sundarijal VDCGokarneshwor ghat - Gokarna VDCGauri ghat - Guheshwori Area KMCAarya ghat - Gausala KMCSankhamul ghat - Sankhamul LSMCTeku Dovan ghat - Teku KMCSundari ghat - Kirtipur KMCDhobi ghat - Lalitpur Jalvinayak ghat - Chovar VDC-14, Kirtipur

Table 5 Environmental impacts of Ghats on Bagmati River

Positive Impacts Negative Impacts

Increase employment opportunity Downstream water pollution/ Ground water pollution

Improve economic activities Effects on micro-climate

Local market development Sedimentation /Siltation

Tax & royalties Air/Soil pollution

Preserves Culture Deforestation (Fuel wood)

  Land Acquisition/ displacement

  Effect on aquatic life

  Child labour Issues

b. Temples Name of temples Location

Sundari Mai - Sundarijal VDCBhara Karneshwor Mahadav - Nayapati VDC-1,Gokarneshwor Mahadev - Gokarna VDC-1Utrabahini Bhairab - Gokorna VDC-7Guheshwori - Guheshwori Area, KMCPashupatinath - Gausala, KMC

Rudreshwor Mahadav - Babaharmahal, KMCBanglamukhi - LSMC Juddeshwor Mahadav - ThapathaliRadhakrishna Mandir - Thapathali, KMCHanuman Mandir - Tripureshwor,KMCBaikateshwor Mahadav - Pachali-12, KMCPachali Bhairav - Pachali-12, KMC.Rammandir - Kupandole, LSMCRadhakrishna mandir (Chintamani Dham)- Teku Dovan, KMCKuleshwor Mahadav - Mahadevsthan, KMCHanuman mandir - Balkhu, KMCRadha Soamisatsang Beas Nepal - Sundari GhatSulakshin Kirtibihar - Sundharighat, ChovarJalvinayak mandir - Chovar -14, KirtipurDakshinkali Mai - Dakshinkali

Table 6. Environmental impacts of temples on Bagmati RiverImpacts

Positive Impacts Negative Impacts

Increase employment opportunity Downstream water pollution

Improve economic activities Soil pollution

Local market development Deforestation (Fuel wood)

Tax & royalties Effect on aquatic life

Preserves Culture Land Acquisition/ displacement

Human resource development  

c. Major Bridges

i) Bridges along the Ring Road:Bagmati – GausalaDhobikhola - ChabahilBishnumati - New Bus ParkBalkhu khola - KhashibazarBalkhu khola - BalkhuBagmati - BalkhuManohara - Balkumari

ii) Bridges inside and outside the Ring RoadKalimati-Teku over Bishnumati Thachal BishnumatiSwoyambhu Bishnumati Thapathali-KupondoleTeku-Kupondole Naradevi-DalluGodawari (Godawari) Gawar (Imadol)Godawarikhola (Lubhu) Dhobichaur-Shova BhegawatiPakanajol-Balaju Mahadev KholaNaikap pool Dillibazar-Old Baneshwor Dhobikhola Sinhamangal-Bagmati

Kalopool (Dhobi khola) Ratopool (Dhobi khola)Babaharmahal (Dhobi khola) Manamatta poolNakkhu pool Sankhu poolManoharapool (Araniko Highway) Bagmati pool (Araniko Highway)

iii) New Bridges in current Construction

Sundarijal VDC - Gagalphedi VDCBuddnagar - Jwagal, LalitpurTripureshwor - gusingal KupoondolChovar - lalitpur

iv) Suspension Bridges

Name Left Bank Right BankSundari Lalitpur KirtipurChovar Saibu Panga BalkumariKhokana Bbungmati ChalnakhelPachali Pachali PachaliNaikhndi Ghat Chhampi PharpingTahchal Tankeshor TahachalJholungepool Balkumari Koteshor

Table7. Environmental impacts of bridges on Bagmati River

Impacts

Positive Impacts Negative Impacts

Increase Accessibility Water logging/ Inundation

Improve economic activities Sedimentation

Affects social movement of people River bed deepening

Support national developmentObstruction on movement of aquatic animals

d. HospitalsTilganga Eye Hospital - KMCOm Hospital - ChabahilMedicare Hospital - ChabahilHAMS Hospital - BuddhanagarParopakar Prasuti Hospital - ThapathaliStar Hospital - Sanepa, LSMCNORVIC Hospital - Thapathali

Table 8. Environmental impacts of hospitals on Bagmati River

Impacts

Positive Impacts Negative Impacts

Increase employment opportunity Air/water/soil pollution

Improve economic activities Noise pollution

Local market development Ground water pollution / ground water table reduction

Tax & royaltiesMixing of toxic waste on municipal waste spreads toxicity

Control diseases Increased insects & vectors

Improve health condition Spreads epidemic diseases

Social mobility Land acquisition

  Possibility of infections

  Gender Issues