COMPARATIVE STUDY OF THE RESERVOIRS

Abstract

“Reservoir sedimentation affects the availability of water storage and thus impairs sustainable water resources management. A reservoir is, of course, merely an artificial lake, and all reservoirs are gradually dying from loss of their capacity caused by deposition of sediment, most of which is transported by inflowing streams. Thus it is seen that though most of the dams are constructed to last almost indefinitely, they will become largely useless from silting long before the dams themselves reach a stage of significant deterioration. Reservoir storage diminishes gradually, without causing instant disaster. Damages become appreciable in a more or less distant future: energy production may drop, irrigation falter, overshadowed by more urgent social issues. The pr0blem 0f sedimentati0n 0f reserv0irs and its effect 0n the useful life 0f reserv0irs is c0mplex. The phen0men0n 0f sedimentati0n and the c0ncept 0f life 0f a reserv0ir and its estimati0n have been studied in depth 0ver many years.”

“The m0st 0bvi0us effect 0f reserv0ir sedimentati0n is the depleti0n 0f water st0rage capacity in the reserv0ir. The decrease 0f st0rage capacity prevents the reserv0ir fr0m supplying the services f0r which it was designed, thus disturbing the ec0n0mic life 0f the regi0n 0r c0mmunity which it serves.”

“This project deals with the analysis of the data that was obtained after the sedimentation studies carried out by CWC for the Salaulim Reservoir on the Salaulim River in Goa State,the Ranapratap sagar Reservoir on Chambal river in Rajasthan state and the Bhima(Ujjani) Reservoir on Bhima river in Maharastra state.” “Reservoir sedimentation assessments have, over the years, been carried out by Hydrographic surveys. However, it evolved into a specialized technique with the development of Differential Global Positioning Techniques (DGPS) in recent years. This technique, which is now increasingly being adopted for the siltation studies of reservoirs in India, enables collection of enough data to map the entire reservoir bottom and then using the standard topographic and mapping programmes evaluate the changes in the reservoir sedimentation.The Hydrographic and topographic surveys of the above discussed Reservoirs were carried out by CWC, in accordance with the prescribed Terms of Reference, using High Technology equipment, namely integrated

Hydrographic Survey System comprising recording type echo-sounder and computer software for interfacing and recording the position and depth data in real time.In this project,we will briefly discuss the methodology of field investigation adopted by CWC to study the reservoir behaviour.” “The trap efficiency is one of the most important properties of a pond or reservoir.The reservoir trap efficiency is defined as the ratio of deposited sediment to the total sediment inflow for a given period within the reservoir economic life time. Trap efficiency is influenced by many factors,of which primarily factors are: the sediment fall velocity ,the flow rate through the reservoir and the reservoir operation rules.In this project,using the Elevation capacity table (furnished by CWC) at different elevations for the reservoirs taken in a study we will obtain a trap efficieny of each reservoir.”