Revised Capacities and Sediment Pattern Assessment in Rajaval and Kharo Reservoirs of Gujarat (India)

Abstract

In this paper, an attempt has been made to compare the revised capacities of Rajaval and Kharo reservoirs of southern Gujarat (India). The image analysis technique of remote sensing data was used to estimate the revised capacity of these reservoirs. Seven Linear Image Self Scanning (LISS III) digital data of IRS 1D/P6 were used in the analysis. The Normalized Difference Water Index (NDWI), band ratio and slicing were used 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. From the analysis, it was observed that 5.043 million cu m of gross storage of Rajaval reservoir has been lost in 25 years (1982-2007) and the average rate of siltation in this reservoir is 0.202 million cu m/year. In the case of Kharo reservoir, 4.332 million cu m of gross storage has been lost in 22 years (1982-2007) and the average rate of siltation is 0.197 million cu m/year. The data of silt surveys in the year 2000 was also used and the pattern of siltation in both reservoirs was analyzed for evaluation periods, namely, impoundment to 2000 (Evaluation Period-I) and 2000-07 (Evaluation Period-II). From the analysis, it was observed that the sedimentation rate increased significantly during 2000-07 in both the reservoirs but Rajaval reservoir needs immediate attention for soil conservation measures because rate of siltation in this reservoir has doubled during this period. The spatial distribution of sediment in both reservoirs indicated more deposition in upper part due to flat topography in that region.