Assessment of sedimentation in Bhakra Reservoir in the western Himalayan region using remotely sensed data

Sediment particles originating from erosion processes in the catchment are propagated along with the river flow. When the flow of a river is stored in a reservoir, the sediment settles in the reservoir and reduces its capacity. Reduction in the storage capacity of a reservoir beyond a limit hampers the purpose for which it was designed. Thus assessment of sediment deposition becomes very important for the management and operation of such reservoirs. Some conventional methods, such as hydrographie survey and inflow-outflow approaches, are used for estimation of sediment deposition in a reservoir, but these methods are cumbersome, time consuming and expensive. There is a need for developing simple methods, which require less time and are cost effective. In this study, a remote-sensing approach has been attempted for assessment of sedimentation in Bhakra Reservoir, located on the Satluj River in the foothills of the Himalayas. Multi date remote sensing data (1RS-1B, L1SS II) provided the information on the water-spread area of the reservoir, which was used for computing the sedimentation rate. The revised capacity of the reservoir between maximum and minimum levels was computed using the trapezoidal formula. The loss in reservoir capacity due to deposition of sediments for a period of 32 years (1965-1997) was determined to be 807.35 Mm', which gives an average sedimentation rate of 25.23 Mm' year". The average rat£ of sedimentation using hydrographie survey data for the same period was 20.84 Mm' year". A comparison of the results shows that the rate of sedimentation assessed using the remote sensing based approach was close to the results obtained from the hydrographie survey.