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.
