1.1 HYDRO POWER SCENARIO IN INDIA

Energy is one of the basic inputs to accelerated economic development. Hydropower is perhaps the oldest and yet most readily exploitable source of energy, with bulk of its potential yet to be harnessed in many countries, including India. Hydroelectric power has become an increasingly important energy source for India’s economic development owing to the availability of water resources in large quantities that can be tapped for power generation. The Central Electricity Authority (CEA) has assessed the hydro potential in the country to the tune of 84,000 MW, at a plant load factor of 60%. Mobilization of resources for achieving self-sufficiency in the power sector assumes high priority in almost all states in the country. In India the power generating capacity of entire country in the year 1971 was as low as 16,000 MW, which has since increased to 95,183 MW in 1996 (Srivastava 1997; MoP 1998). Despite the tremendous progress that has been made in the hydro power sector, most regions in our country still face acute power shortage. The per capita electricity consumption in India, which is close to 270 units, is still among of the lowest rates estimated for the developing countries of the world. In the developed countries, the level of per capita power consumption ranges between 8000 units to 25,000 units per year. In its pursuit to increase the power generating capacity, India, has adopted the blend of thermal, hydel and nuclear sources. For the 8th plan (1992-97), the CEA had estimated a need based capacity addition of 48,000 MW which was reviewed and brought down to 30,538 MW to confine the increase in capacity that could remain dependent on available resources. At present the country suffers an average shortage of 8% and peaking shortage of 19%. Even with the planned capacity addition of over 30,000 MW in the 8th plan, the shortages in power capacity would not be overcome. In view of this backdrop, the hydro-based power projects become a necessity for harnessing the energy from a renewal resource like water. In India there are over 1,554 large, medium and small dams (Anon., 1982). Another 200 Hydroelectric Projects are under construction or are being planned (Sharma, 1985).

1.2 HYDROPOWER GENERATION AND ENVIRONMENTAL IMPLICATIONS

After the Stockholm U.N. Conference in 1972, an increasing concern has been expressed over the adverse environmental impacts of water projects in general and creation of man-made reservoirs by building dams in particular (Hafez & Shenouda 1978). Despite the positive gains offered by hydropower projects, one can not deny the fact that the creation of dams and reservoirs have significant environmental repercussion on physical, chemical and biological aspects of the environment. Any change in natural topography and water regime of a river will affect its ecological and biological diversity. A major conflict arises between developmental progress and biodiversity conservation when projects are sited in the wilderness tracts because such projects interfere with various wildlife conservation objectives and impact upon prevailing patterns of land allocation and resources for people (Anon, 1993). With the implementation of such projects, the wild habitats come under greater biotic pressures thus compounding the threats to conservation of flora and fauna. Such impacts on wildlife and forest have been clearly manifested in Mananthody Hydroelectric Project in Wynad (Balakrishnan and Abraham, 1988). Significant impacts on wildlife were also predicted in the event of implementation of proposed Bodhghat Project and the projects proposed downstream of Bodhghat in Bastar (Panwar et al., 1990). The Bodhghat Project, which would have posed a major impact due to destruction of the habitat of the only population of wild buffalo in Central India, was eventually abandoned. The Silent valley Project, yet another ambitious project was strongly opposed and eventually abandoned in the face of threats it posed to the conservation of biodiversity of the virgin rain forests. The submergence of vast tracts of forests by the hydel projects can perhaps be singled out as the greatest cause of threat to biodiversity of any natural environment. This has been well illustrated by Idukki and Periyar projects (Mohanty and Mathew, 1987; Nair and Balasubramanyam, 1985). The proposed Narmada valley Project which involves construction of thirty major and 135 medium dams would submerge vast stretches of forest in Satpura and Vindhyan ranges. This can be seen as a direct threat to conservation of wildlife habitats in Central Indian forests (Rajvanshi et al, 1994). Fragmentation of natural habitats is yet another consequence of most developmental activities. The Ramganga reservoir and Chilla Hydro Power Channel in the outer Himalayas and Siwaliks in Uttar Pradesh have fragmented the home range of north-western elephant population (Johnsingh et. al., 1990).

Decimation of forests in the catchment area are also expected to lead to high rates of siltation in the reservoirs created by dams, which ultimately reduce the projected life of the project.

1.3 HYDRO POWER DEVELOPMENT SCENARIO IN SIKKIM

Before Sikkim became the 22nd state of India in 1975, the power requirement in this state was very limited. However, with the increase in the power demand it became necessary for Govt. of Sikkim to tap its vast and unexplored water resources.

Sikkim has innumerable streams and rivers flowing down the glaciers, which provide abundant potential of Hydroelectric power projects. It is estimated that Sikkim has a potential to produce 8000 MW seasonally and about 3000 MW power during winter months. So far the state has been able to tap only 33.10 MW till the end of 1996-97 through projects which are largely the run of the river schemes.

The river Teesta, which is one of the major rivers originating in the state has tremendous potential for promoting power generation as the river descends from an elevation of about 3600 m to about 300 m over a distance of 175 km.

1.3.1 Teesta river: A Major Source for Harnessing Energy in Sikkim

The river Teesta, fed by the snow and glaciers of Kanchenjungha and great Himalayas, originates in north Sikkim at an elevation of 8400 m above mean sea level. The river rises in mountainous terrain and is formed mainly by the union of two hill streams Lachen chu and Lachung chu at Chungthang in north Sikkim. It is a perennial river and flows through the territories of Sikkim, west Bengal and Bangladesh. The river flows through Sikkim for about 152 km and thereafter it enters west Bengal at Rangpo, about 16 km north east of Darjeeling.

River Teesta flows north south along the length of the state of Sikkim and forms the single major river in the state. The state of Sikkim has an average annual rainfall of 650mm to 2500mm making Teesta, a perennial river with substantial flow even in the lean season. Enormous fall of the order of 3600 m over a river length of 175 km along the course makes river Teesta an ideal source for hydropower generation.

The following schemes in the Teesta river in cascade development were planned:

Stage I. Utilizing a gross head of 730 m for firm power generation of 96 MW
Stage II. Utilizing a gross head of 1038 m for firm power generation of 224 MW
Stage III. Utilizing a gross head of 800 m for firm power generation of 180 MW and installed capacity of 1200 MW
Stage IV. Utilizing a gross head of 183 m for firm power generation of 64 MW
Stage V. Utilizing a gross head of 217 m for firm power generation of 100 MW and installed capacity of 510 MW.
Stage VI. Utilizing a gross head of 40 m for firm power generation of 25 MW

1.3.2 Present Project: Teesta Hydroelectric Stage - V

Teesta Hydroelectric Project, Stage - V for which this ecological assessment was undertaken has been planned for commissioning by the year 2007-2008. Under this stage of Teesta basin development, the waters of Teesta will be diverted through a tunnel of about 18 km length by constructing a suitable dam at Dikchu 2 km downstream of confluence of Dikchu with the Teesta. The dependable discharge available through the year has been assessed as 60 cumecs and the gross head available is 200 m. The Power house will be located near Singtam about 4 km upstream of the confluence of Rongnichu with Teesta and is expected to generate 100 MW of firm power with an installed capacity of 510 MW.

1.4 NEED FOR AN EIA

Implementation of river valley projects in the past have provided ample experiences of the neglect of environmental and social considerations during project siting, planning and implementation. This has resulted in the decimation of forest and loss of biodiversity. It has been estimated that nearly five lakh hectares of forest land have already been destroyed as a result of the construction of various river valley projects in India between 1950 and 1975 (Goldsmith and Hildyard, 1984). The conservation of biodiversity can not be achieved until degradational trends are arrested. Environmental impact assessment can provide the framework for incorporating environmental concerns in development planning. The effectiveness of such an approach however depends strongly on its application that is dictated by the legislative machinery.

The promulgation of Wildlife (Protection) Act (1972), Forest (Conservation) Act (1980), and the Environmental (Protection) Act (1986), the formulation of the National Forest Policy (1968) and the guidelines for River valley Projects and siting of Industry (MOE, 1984 & 1990), have now made statutory provisions and have laid a firm policy approach for strengthening environmental conservation in India. The increasing awareness of the environmental protection and statutory provisions have also lead to the establishment of mandatory provisions of the Environmental Impact Assessment (EIA) prior to seeking environmental clearance for any mega development project (EIA Notification, 1994).

As per the Environmental Impact Assessment Notification (1994), Ministry of Environment and Forests, Government of India, twenty nine categories of projects have been included under schedule I Projects. In accordance with the statutes of the above notification, no new developmental projects can be undertaken in any part of India unless environmental clearance has been accorded by the Central Government. The Proposed Teesta Stage - V Hydroelectric Project falls under the Schedule I Projects. This makes its environmental assessment mandatory prior to seeking the environmental clearance for implementation of this project.

1.5 SCOPE OF WORK

In accordance with the statutory requirements under the EIA notification, M/s National Hydroelectric Power Corporation Ltd. (NHPC), Faridabad, the proponents for the Teesta Hydroelectric Project, Stage - V would be required to prepare a comprehensive EIA report prior to applying for environmental clearance of this project. NHPC approached WII for conducting the ecological assessment of the above Project, vide their letter No. NH/PB/ENV.67/121 (Appendix – I).

The following are the terms of reference for work to be undertaken by WII under the consultancy offer of NHPC Ltd.

1. Assessment of the impacts of the project on biohabitats and the biodiversity (flora, fauna) of the region.
2. Preparation of the action plan for remedial measures where necessary, giving details of the year wise fund allocation and agencies that will be involved in implementing the environmental management plans.
3. Evaluation of the impacts of the proposed project on the butterfly species and preparation of the conservation plan for the butterfly species and their habitat.