47-Sediment rate evaluation of Somasila Reservoir Andhra Pradesh using remote sensing technique

Abstract

Periodic surveys of reservoirs are essential to evaluate the decrease in storage capacity due to inflow and trapping of sediment. Conventional hydrographic surveys are time consuming, labour intensive and expensive. Satellite remote sensing techniques provide time and cost effective approach for the periodical capacity surveys. Waterspread area, estimated from satellite data at different storage levels in a hydrologic year provides an important input for the estimation of the revised capacity of a reservoir. Comparison of previous and revised capacity yields the loss in storage due to sediment deposition. In this study Somasila reservoir located on Pennar River that flows through Nellore district of Andhra Pradesh, South India has been chosen for evaluating the capacity loss using Indian Remote Sensed Satellite, LISS-III image data. Digital satellite data pertaining to 2002 was acquired for seven different elevations and the revised water spread areas were extracted. Using trapezoidal formula, the revised volume between the elevations 83.17 m and 94.39 m was computed. The results show that the loss in capacity is 23.96 million cubic metre during the period 1987 to 2002. If uniform rate of sedimentation is assumed, in 15 years of operation of the reservoir, then the sedimentation rate would be 1.597 M Cum per year.