Environmental impacts of proposed Baddegedara impounding reservoir

Abstract

This research study, "Environment Impacts of Proposed Baddegedara Impounding Reservoir" was conducted in relation with the feasibility study for water supply and sewerage for Koggala Export Processing Zone and the surrounding license Zone.The project area consist of Talpe, Habaraduwa, Koggala EPZ and Coastal belt. Ahangama, Dikkubura and Imanduwa. People living in the area excluding Koggala EPZ have to depend on individual water sources. The majority of the population depend on ground water drawn from shallow dug wells. The main complaint of people living along the coast in the project area regarding the water quality of their dug wells in salinity. Most of these wells are shallow and not covered or protected. Water obtained from these wells is therefore at high risk to be polluted with organic matter.Study was conducted by having field surveys. When selecting a source for the project area whenever possible first choise was given to ground water which requires the least treatment. But the test drilling programme shows that it is impossible to get total water requirement by ground water itself. Therefore we have to go for a surface water source close to the project area.Proposed impounding reservoir at Baddegedera is located nearest to the project area. Reservoir catchment is the upper most reign of a tributary of Polwatta ganga which meets the main river about 2 Km upstream of Kananka. This catchment is located near to the catchment of Hiyare impounding reservoir which is presently supplying part of water to the Galle Municipality. Environment Impacts were assessed by using a matrix called Environment interaction matrix. In this method a list of all potential impacts of the project were prepared and each individual impact was assessed. The matrix was analyzed by using the Battle's environment evaluation system. In this method the weights of the parameters were assigned depending on the relative importance of the parameters. Value function for the variation of environmental quality index with the change in each of the environmental parameter had to be determined. The environmental quality (e.q.) index with project and the e.q. index without project were evaluated for each environment parameter. Then the environment impact unit was obtained by getting the product of the relative weight of the parameter and the e.q. index. In this method positive net change of product means beneficial impacts whereas negative product means adverse impacts. The topography of the area does not lend itself to the fashioning of a deep lake. According to past studies done by various people the ideal wildlife lake is shallow with gently slopping shore. This type of situation could be expected from the proposed impoundment. These natural qualities of the habitat could be further augmented by various management techniques such as the restriction of the area of impoundment and catchment.