Assessment of Reservoir Sedimentation Using Indian Satellite Image Data

Abstract

Periodic surveys of the reservoirs are essential to evaluate the decrease in storage capacity due to inflow and trapping of sediment. Conventional hydrographic surveys are time-consuming, labor-intensive and expensive. Satellite remote sensing techniques provide time and cost-effective approach for the periodical capacity surveys. Water-spread area estimated from the 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 survey yields the loss in storage due to sediment deposition. In this study, the Somasila reservoir, located on the Pennar river that flows through the Nellore district of Andhra Pradesh, has been chosen for evaluating the capacity loss using Indian Remote Sensed Satellite image data. Digital satellite data pertaining to the water year 2002 were acquired for seven different water levels of the reservoir, which ranges from minimum draw down level (MDDL) to full reservoir level (FRL), and the revised water-spread areas were extracted. Using trapezoidal formula, the revised volume between the water level 83.17 m and 94.39 m was computed. Analysis of the results showed that the loss in capacity is 23.96 M cum 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 is 1.597 M cum per year.