217-Assessment of Reservoir Sedimentation in Maharashtra.

Abstract

In Maharashtra, huge water storage potential is created so far by constructing several dams of major, medium and minor category. Some of these have been seriously affected by siltation, pollution, growth of water weeds reducing the water storage potential of these reservoirs. In many cases the rate of sedimentation in reservoirs is observed to be much higher than the rate considered while designing. Increasing population and growth in industrial sector as well as rapid urbanization is putting extra burden on existing water storages. It has there fore become necessary for the planner to know silt load accumulated in the reservoirs to use the present useful contents judiciously and optimally. In this direction a review of the silt load in many reservoirs is taken in the State by conducting sediment assessment surveys of these reservoirs. Maharashtra Engineering Research Institute, Nashik, a Research & Development wing of the State Water Resources Department, has so far conducted sediment assessment surveys of about 45-50 reservoirs, The surveys for major and medium sized water bodies were conducted using satellite remote sensing technique and DGPS based bathymetric survey and for small water bodies, conventional hydrographic surveys were conducted. These reservoirs are located in different geographical parts of the state representing different hydrological and catchment characteristics. The observed silt load in many reservoirs is found to be higher than the designed one. In general it was also observed that the silt rate is more in case of reservoirs having smaller catchment area. But at the same time, the annual percent loss in storage on an average is less than 0.3% which is not alarming one. In case of reservoirs in non ghat area of deccan plateau, the average rate of siltation is observed to be more than the design rate but is near about the rate now prevailing in the state and the annual percent loss in storage capacity is in between 0.3% to 0.5%.