Assessment of revised capacities and trend analysis of sedimentation in reservoirs of southern Gujrat (INDIA)

Abstract

The information on rate and extent of reservoir sedimentation is essential for taking up appropriate measures in controlling the sediment inflow, to obtain updated assessment of useful life of the reservoir and to decide on the optimum reservoir operation schedule based on realistic assessment of available storage. The trend analysis of sedimentation in Shetrunji, Rajaval and Kharo reservoirs of South Gujarat (India) have been made by computing the revised capacities using digital image analysis techniques of remote sensing data and other silt surveys. Seven Linear Image Self Scanning (LISS III) digital data of Indian Remote Sensing (IRS) satellite IRS-1D/P6 have been used and normalized difference water index (NDWI), image rationing and slicing methods have been applied to classify the water and non-water pixels from the images using Integrated Land and Water Information System 3.0 (ILWIS 3.0), a GIS software. Results of the study indicates that the average rate of siltation in these reservoirs have increased from 0.06 M. cum/100 sq km/year up to year 2000 to 0.11 M. cum/100 sq km/ year from 2000 to 2007. The average rate during the whole period of siltation in these reservoirs may be computed as 0.073 M. cum/100 sq km/year. The analysis of sedimentation pattern in these reservoirs indicate that siltation in upper part of these reservoirs has increased significantly during 2000 to 2007. Under present condition, the Joglekar’s equation should be used to calculate the rate of sedimentation in reservoirs of South Gujarat. The substantial increase in the rate of siltation emphasized the urgent need of modification in reservoir operation plan and development of catchment area treatment plans in upstream of these reservoirs.