EIA for the proposed extension of the Karnafuli hydroelectric power plant

Abstract

The Kaptai Lake is a storage reservoir and a fresh water wetland having maximum standing water area of 750 km2 at highest water level of 33.222 m (109ft) MSL. The main use of the lake water is hydropower generation, flood control, fisheries and navigation. Secondary use of the lake water is to develop wildlife, reserve-forest, recreation and reduction of saline effect in coastal area. The basic purpose of the proposed extension of the Karnafuli hydroelectric power plant project (6th and 7th units) is to optimize the reservoir operation. Mitigation of flash flood at downstream of the dam during spill period and raise the total rated capacity from its existing 230 MW to 330 MW are additional objectives. Increase of rated capacity is planned by installing the new power generating units (50 MW x 2). However, it is expected to be achieved by minimizing spillage water through spillways and by raising the Reservoir Rule Curves Low Water Level from 76 feet (23. I60m) MSL to 97 feet (29.565m). Methodology adopted for accomplishing ElA is the Environmental Evaluation System (EES), used in the Asia Pacific Region and for this 54 environmental parameters are selected. Out of the 54 selective environmental parameters, there are 24 non-effected parameters. There arc 3 negatively effected parameters, which are: temperature stratification, loss of agricultural land, crop production. There are 27 positively effected parameters, which include: forest, wildlife, species diversity (both terrestrial and aquatic), rare and endangered species (both terrestrial and aquatic), fisheries (reservoir and downstream), aquatic weed, benthos, eutrophication, soil erosion, flow variation, DO, BOD5, pH, salinity intrusion, water table, nutrition, employment opportunity, flood control, industrial activity, power supply, aquaculture, navigation, water quality, recreation. ElA by using the Environmental Evaluation System (EES) methodology show overall positive values of environmental impact units (ElUs). Improvement of ecological category is 225 EIUs, and that of physico-chemical category is 145 EIUs and humaninterest category is 395 EIUs. Conducting meeting with the public and inhabitants of the area, local government, tribal people, etc. should develop public awareness of the positive and negative aspects of the overall project. Their feedback should be incorporated into the project program and planning. This should be conducted regularly at every stage of the project to reduce/mitigate the adverse view of the local and affected people. Thus, within the brief extent of the work conducted in this study it may be said that the proposed extension project of Karnafuli Hydropower Plant may provide an overall positive impact on the environment if installed and maintained properly with the appropriate mitigation measures for the negative impacts.