IMPACTS OF HYDROPOWER PROJECTS ON RIVER WATER QUALITY

Abstract

Water is essential for sustenance of all forms of life on earth. It is not evenly distributed all over the world and even its availability at the same location is not uniform throughout the year. Optimal management of river water resources is essential to meet the growing demand. So dams and reservoirs are constructed for storing surplus river waters available during wet:.periods and utilizing the same during lean periods. These dams and reservoirs are playing• dual role of harnessing the river waters for accelerating socio-economic growth and mitigating the miseries of a large population of the world suffering from the vagaries of floods and droughts. Energy requirements must be met for Industrial and for socio-economic prosperity of a country. Hydropower is one of the potential sources for meeting the growing energy needs of the country. A judicial mix of hydropower in the energy portfolio can also contribute to energy security, reduction of greenhouse gas -emissions, meeting the peak demand and also increased flexibility in grid operation. Besides, projects may also be conceived as multi-purpose ones contributing not only to power but also to irrigation, flood control, navigation, etc. All hydroelectric structures affect a river's ecology mainly by inducing a change in its hydrologic characteristics and by disrupting the ecological continuity of sediment transport and fish migration through the building of dams, dikes and weirs. The extent to which a rive'r's physical, chemical and biological characteristics are modified depends largely on the type of HPP. It. is required to perform Environmental Impact Assessment procedures before building or reconstruction of hydro power plants exceeding the power of more than 1 MW. The change of surface water quality is one of the main indicators used for the assessment of impacts on the environment. This dissertation investigates the cumulative impact of commissioned and under development hydro power projects on the water quality of the Alaknanda River and its tributaries. Field visits, were conducted for collection of water quality samples and hydro dynamic data at two project sites on Alaknanda River. The data for remaining projects is taken from the : study on "Assessment of Cumulative Impact of Hydropower projects in Alaknanda and Bhagirathi Basins up to Devprayag" conducted by AHEC, IIT Roorkee. iii QUAL2K modeling software is employed for prediction and assessment of change in surface water quality. Assessment of length of river- stretch required for the water to get rejuvenated is carried out for commissioned project. The models are simulated by considering many parameters pertaining to Metrological, Topographical, Hydraulic, Hydrological and Water Quality Parameters. The results are analyzed by considering high and low environmental flows. When six . standard water Quality parameters are considered the impact of the proposed and commissioned projects is found to be insignificant. Water quality was found to be of class—A.