Project induced impacts on fisheries resource and their mitigation approach in the Kali Gandaki "A" hydroelectric project, Nepal. (by Upadhaya, K.K. and B.C. Shrestha)

Ministry of Agriculture, Department of Agriculture, Fisheries Development Directorate
Kali Gandaki Environmental Management Unit

ABSTRACT

The Kali Gandaki "A" Hydroelectric Project is under construction in Western Nepal. The project will have significant impacts on the fisheries resources of the River Kali Gandaki. Environmental Impact Assessments (EIA) recommended mitigation and protection measures to include trapping and hauling fish up and downstream, screened intakes, riparian release facility and a fish hatchery. The mitigation programme has encountered several challenges related to extreme river conditions, lack of biological information, and difficult logistics. In addition, Nepal has little experience in developing and implementing environmental mitigation for hydroelectric projects. The lessons learned will have positive implications for mitigation of other hydropower projects in Nepal and Asia.

1. BACKGROUND

Nepal has extreme topography that shapes its natural resources. The altitude varies from 8848 m to 500 m north to south and the associated climate diversity supports rich flora and fauna. Nepal has high Himalayan mountains in the north; to the south are mid-hills, foothills and the lowland Terai with broad valleys, fertile plains and tropical jungles. Approximately 6 000 rivers and streams fed with snowmelt and rainwater traverse the mountain ranges, valleys and plains to feed into the Bay of Bengal, India.

Despite the abundant water resources Nepal experiences lack of electricity, which affects its economy. Out of its 25 million people only 10% have access to electricity. Looking at this great demand, His Majesty's Government of Nepal (HMG/N), Ministry of Water Resources (MWR) and Nepal Electricity Authority (NEA), with the help of international funding agencies, is supporting the development of several hydropower projects. Kali Gandaki "A" Hydroelectric Project (KG"A"HEP) is the biggest undertaking in Nepal capable of supplying 144 MW. The Project has been under construction from 1997 and was expected to be completed by 2001.

An Environmental Impact Assessment (EIA) was conducted as part of feasibility studies as required by Nepalese regulations. EIA has included physical, biological, socio-economic and cultural considerations. One of the major concerns was impact on fisheries resources of the Kali Gandaki River, which supports a diverse fish community which is heavily fished.

This paper briefly describes the project, its impacts and mitigation efforts. The mitigation programme is in its 4th year and has made significant progress. However, limitations are apparent, largely driven by biological, hydrological, cultural and management factors. We speculate on the nature of these challenges and how these might be avoided in future such projects in Nepal and other developing countries.

2. BRIEF DESCRIPTION OF THE PROJECT (Fig.1)

The KGA project is located 500 m below the confluence of the Kali Gandaki and the Andhikhola at Mirmi. The river flows west, turns south and east to form a 50 km loop and reaches the powerhouse site at Beltari. Both Mirmi and Beltari villages are in the Sri Krishna Gandaki Village Development Comity of Syangja District. A 44 m high by 110 m long concrete diversion dam will create a reservoir of 65 ha stretching 5.3 km, with an average depth of 12 m and operating level between 518-524 m. From the desanding basin at the head works site, water low in sediments will be routed into a 5.9 km tunnel and enter a power plant equipped with a surge tank, pressure shaft, three power units, transformer, draft tube gate and a tailrace where it will be released back into the river. Power will be distributed to Nepal's national power grid using transmission lines that tap into substations at Pokhara and Butwal. Annual generation is estimated at 840 GWh. Figure 1 shows the location.

Morrison Knudsen International (MKI), USA, provides the engineering design for the project and Impregillo S.p.A. (IGL), Italy, is doing the civil construction. The KGA project is owned and operated by the NEA.

3. RIVER CONDITIONS AND FISHERIES RESOURCES

3.1 River conditions

The Kali Gandaki River originates from Tibetan Plateau, north of Nepal. The river runs between elevations 5 500 m and 1 250 m forming deep gorges. Four tributary streams join it as the river loses elevation and enters the KGA project area. Above the dam it is joined by the Andhikhola; between the dam and powerhouse Badigarh and Ridikhola join it. Below the powerhouse, it joins with the Trisuli and forms the Narayani River before it flows into the Gangetic plains of India and finally into the Bay of Bengal.

Various sections of the river have different gradients. The upper section is snow-fed, steep and with swift current flowing over rocks; the middle is rain-fed, has flatter profile; and the lower section has warm water, low gradient and the river is productive. At the dam site the suspended sediment load reaches up to 50 g/L during high flows. During dry season the river is clear. Water current velocity ranges from 1.5-2.5 m/sec, but reaches 10 m/sec during monsoon. The riverbed is covered by boulders, rocks and gravel.

3.2 Fisheries resources

The Kali Gandaki River has a number of fish species adapted to the extreme gradient. The fish support subsistence, commercial and sports fisheries. The annual catch from the river is estimated at between 80 to 150 tons. The principal species are snow trouts, mahseer, carp, catfish, eel, murrel, loach and barbs. Mahseer (sahar), snowtrout (asla), catfish and eel are sport fish.

Feasibility studies recorded 57 species within the project area. These fish have adapted to the extreme flow and turbidity. Migration patterns include long distance (to and from Terai or Bay of Bengal); medium distance, and residents (moving from the mainstream to immediate tributaries). Upstream migration starts at the beginning of monsoon which triggers spawning behaviour, and downstream migration starts when water levels in the tributaries subside. The catadromous eel is also abundant in the Kali Gandaki River.

Fig. 1 - Location of the kali Gandaki 'A' Hydroelectric Project area and major project features

4. PROJECT IMPACTS AND MITIGATION MEASURES

The Environmental Impact Assessment (EIA) was the framework used to identify project impacts and mitigation measures for the fisheries resources and these are represented in Table 1.

4.1 Barrier effect

The diversion dam will physically block the upstream and downstream migration of fish resulting in reduction in spawning success due to loss of habitat and ultimately reduction of fish stocks. Evidence of these effects has been observed in the rivers Andhikhola, Marsyangdi, Trishuli and other hydropower or irrigation dams of the country.

Table 1

Summary of the Kali Gandaki 'A' Hydroelectric Project impacts on fisheries and ethnic groups

A fish trapping and hauling programme would facilitate upstream passage and could be coordinated with hatchery operation. Fyke nets, hoop nets and fish wheel traps were considered for testing along with local dipnets, cast nets, sakhar and bamboo traps. Current efforts focus on establishing an effective manner in which to do live trapping. However, the testing of these traps showed low catch per unit effort, with total catches ranging from a few kilograms to several hundred kilograms of targeted species. The testing has been difficult due to large fluctuations in water level (1 to 9 m), high sediment load rendering fish capture techniques that rely on visual observation unusable, disturbances due to project construction activities (regular gravel and boulder takeout, muck disposal in the river), etc. In addition, due to lack of proper gears and equipment, inconsistent staffing and inexperience, the programme has had to run on a limited scale. The diversion dam is the most suitable place for establishing a permanent trapping station as migrating fish become stranded and congregate there.

4.2 Entrainment

Entrainment rate could not be quantified due to lack of biological information on downstream migration pattern. Entrainment of out-migrants is a major concern because the river will be 90% diverted during the dry season. To avert entrainment, a trash rack and louver system will be incorporated into the dam. Out-migrants will be diverted away from the intake and into a downstream riparian release facility.

4.3 Dewatering

During the dry season the 50 km reach between the diversion dam and the powerhouse (Kali Gandaki Loop) may be dewatered to a point where there is a substantial loss of aquatic habitat, no migration, and reduced access to spawning or nursing grounds. The uppermost 13 km is particularly vulnerable as there are no tributaries to contribute flows.

A 4 m³/sec minimum riparian release is suggested to be viable in terms of the amount of habitat saved and cost.

4.4 Fish hatchery

A fish hatchery is being constructed to mitigate the combination of impacts caused by the project. This is a multiple species (both cold and warm water) fish hatchery with a main hatchery building, hatching and holding facility, indoor and outdoor nursing/rearing facility, a laboratory and raceways. The hatchery will use water from the tailrace to supply a terraced system of ponds and raceways.

Targeted species are mahseer or sahar (Tor spp), asla or snowtrout (Schizothorax spp), katle (Neolissocheilus spp), jalkapoor (Clupeisoma spp), gonch or bagarid catfish (Bagarius spp), rajbam or fresh water eel (Anguilla spp) and others. Annual goals are 30 million eggs, 10 million hatchlings or fry and 2 million fingerlings to be produced and released into the Kali Ganga River system.

The reservoir will create opportunities for aquaculture in net cages and enclosures, sport fishing and boat transportation. However, the previously available five-day rafting trips (from Baglung to Ramdi) will be limited to three days (Baglung to Setibeni or Mirmi).

4.5 Bote ethnic group

Approximately, 150 Bote families reside near the KGA project area including Andhimuhan, upstream and downstream of the Kali Ganga River. They make their living by fishing, boat handling and as labourers. When completed the project may displace or reduce fishing opportunities. As mitigation, the project has provided employment during construction, housing and school facility for these poor communities.

Mitigation in the KGA project is implemented through an adaptive strategy that evaluates existing measures and develops alternatives, as information becomes available, involving continued monitoring, development and testing of new strategies. A large component of this adaptive management will be new and ongoing research to understand native fish populations.

4.6 Concerns

Lack of biological information: There is little information on fish abundance, migration and spawning behavior in the Kali Gandaki River.

Interim mitigation: The construction company is responsible for implementing mitigation measures directed by engineers but lacks qualified personnel for interim mitigation. The construction of the project is a higher priority for the IGL engineers and the employer whereby little response is given to mitigation efforts. Environmental mitigation for hydroelectric projects is very new to Nepal. There is little awareness of environmental issues that influence the success of mitigation efforts.

5. CONCLUSIONS

The fisheries mitigation programme is new and in its infancy. Challenges to be faced are lack of biological information and awareness, difficult trapping conditions, logistics and management inconsistencies. It is hoped to overcome obstacles as construction is completed, techniques are refined and more biological information becomes available. On-site research is needed to understand how the fish population responds to a new hydroelectric project. Mitigation efforts should consider what biological information exists prior to construction, especially in countries that emphasize economic development over environmental concerns.