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

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. In the present study, a comparison of sedimentation status was made in Rajaval and Kharo reservoirs situated in Bhavnagar district of Gujarat. 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 (1985-2007) 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