Hydrology And Environmental Perspective Of Bagmati River Basin

Hydrology and Environmental Perspective of Bagmati River basin By Madhav Narayan Shrestha, Ph.D Email: [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)

Basin-1 Basin-2 Basin-3 Basin-4 Basin-5

574.50 306.62 782.40 1036.48 1000.00

Drainage Length (km)

No. of Raingauges

1909.434 18 1473.258 3 3402.050 1 4126.244 0 1032.242 4 Total Area = 3,700 sq km

Drainage Density

Gauge Density

3.324 4.805 4.348 3.981 1.032

1 in 31.92 1 in 102.21 1 in782.40 1 in 250.00

Table 2 Drainage hierarchy length S.N. 1 2 3 4

Drainage Hierarchy First Order Second Order Third Order Fourth Order

Drainage Length (km) 863.692 291.234 260.678 113.557

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 withdraws Types of Industry

No

Water Withdrawn Source

Total

Av. Rate (l/d)

Quantity(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

Many

Municipal + Pvt. Supply

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

Slaughter House

(Source: FNCCI directory (2003-2005)

200,000 (LS)

Remarks

Not Regd.

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 River Location

pH

Conductivity.

TDS

NH3

NO3

NO2

DO

COD

BOD5

μmos/cm

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

770

420

Bagmati at Teku

7.2 3

1460

825

84.52

0.38

1.83

0

Bagmati at Khokana

7.4 8

874

468

45.64

0.32

0.67

1.90

Bagmati at d/s Kulekhani

7.8 8

662

345

23.18

05.03

1.29

6.90

37.5

16.50

Bagmati at U/S of the Kokhajor

7.2 6

246

154

4.73

0.11

0.17

6.30

82.50

34.00

Bagmati at D/S of the Chandi

8.3 6

446

254

0.07

ND (<0.02

ND (<0.05 )

6.30

8

1.40

Bagmati at Indo Nepal Border near Gaur

7.8 9

234

172

0.14

ND (<0.02 )

0.07

6

26

7

390

195

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 Bhara Karneshwor Mahadav ghat Kagbani ghat Gokarneshwor ghat Gauri ghat Aarya ghat Sankhamul ghat Teku Dovan ghat Sundari ghat Dhobi ghat Jalvinayak ghat

-

Location Nayapati VDC-1, KMC Border of Gagalfidi and Sundarijal VDC Gokarna VDC Guheshwori Area KMC Gausala KMC Sankhamul LSMC Teku KMC Kirtipur KMC Lalitpur Chovar VDC-14, Kirtipur

Table 5 Environmental impacts of Ghats on Bagmati River Positive Impacts Increase employment opportunity Improve economic activities Local market development Tax & royalties Preserves Culture

b. Temples Name of temples Sundari Mai Bhara Karneshwor Mahadav Gokarneshwor Mahadev Utrabahini Bhairab Guheshwori Pashupatinath

Negative Impacts Downstream water pollution/ Ground water pollution Effects on micro-climate Sedimentation /Siltation Air/Soil pollution Deforestation (Fuel wood) Land Acquisition/ displacement Effect on aquatic life Child labour Issues

-

Location Sundarijal VDC Nayapati VDC-1, Gokarna VDC-1 Gokorna VDC-7 Guheshwori Area, KMC Gausala, KMC

Rudreshwor Mahadav Banglamukhi Juddeshwor Mahadav Radhakrishna Mandir Hanuman Mandir Baikateshwor Mahadav Pachali Bhairav Rammandir Radhakrishna mandir (Chintamani Dham)Kuleshwor Mahadav Hanuman mandir Radha Soamisatsang Beas Nepal Sulakshin Kirtibihar Jalvinayak mandir Dakshinkali Mai -

Babaharmahal, KMC LSMC Thapathali Thapathali, KMC Tripureshwor,KMC Pachali-12, KMC Pachali-12, KMC. Kupandole, LSMC Teku Dovan, KMC Mahadevsthan, KMC Balkhu, KMC Sundari Ghat Sundharighat, Chovar Chovar -14, Kirtipur Dakshinkali

Table 6. Environmental impacts of temples on Bagmati River Impacts Positive Impacts Increase employment opportunity Improve economic activities Local market development Tax & royalties Preserves Culture Human resource development

Negative Impacts Downstream water pollution Soil pollution Deforestation (Fuel wood) Effect on aquatic life Land Acquisition/ displacement

c. Major Bridges i) Bridges along the Ring Road: Bagmati – Gausala Dhobikhola Chabahil Bishnumati New Bus Park Balkhu khola Khashibazar Balkhu khola Balkhu Bagmati Balkhu Manohara Balkumari ii) Bridges inside and outside the Ring Road Kalimati-Teku over Bishnumati Swoyambhu Bishnumati Teku-Kupondole Godawari (Godawari) Godawarikhola (Lubhu) Pakanajol-Balaju Naikap pool Dhobikhola

Thachal Bishnumati Thapathali-Kupondole Naradevi-Dallu Gawar (Imadol) Dhobichaur-Shova Bhegawati Mahadev Khola Dillibazar-Old Baneshwor Sinhamangal-Bagmati

Kalopool (Dhobi khola) Babaharmahal (Dhobi khola) Nakkhu pool Manoharapool (Araniko Highway)

Ratopool (Dhobi khola) Manamatta pool Sankhu pool Bagmati pool (Araniko Highway)

iii) New Bridges in current Construction Sundarijal VDC Buddnagar Tripureshwor Chovar

-

Gagalphedi VDC Jwagal, Lalitpur gusingal Kupoondol lalitpur

iv) Suspension Bridges Name Sundari Chovar Khokana Pachali Naikhndi Ghat Tahchal Jholungepool

Left Bank Lalitpur Saibu Bbungmati Pachali Chhampi Tankeshor Balkumari

Right Bank Kirtipur Panga Balkumari Chalnakhel Pachali Pharping Tahachal Koteshor

Table7. Environmental impacts of bridges on Bagmati River Impacts Positive Impacts Increase Accessibility Improve economic activities Affects social movement of people Support national development

Hospitals Tilganga Eye Hospital Om Hospital Medicare Hospital HAMS Hospital Paropakar Prasuti Hospital Star Hospital NORVIC Hospital

Negative Impacts Water logging/ Inundation Sedimentation River bed deepening Obstruction on movement of aquatic animals

d.

-

KMC Chabahil Chabahil Buddhanagar Thapathali Sanepa, LSMC Thapathali

Table 8. Environmental impacts of hospitals on Bagmati River Positive Impacts Increase employment opportunity Improve economic activities Local market development

Impacts Negative Impacts Air/water/soil pollution Noise pollution Ground water pollution / ground water table reduction

Tax & royalties Control diseases Improve health condition Social mobility

Mixing of toxic waste on municipal waste spreads toxicity Increased insects & vectors Spreads epidemic diseases Land acquisition Possibility of infections Gender Issues