CS(AR)-24/98-99 : Capacity evaluation of Bhakra reservoir using digital analysis of satellite data

Abstract

Soil erosion. its transportation and subsequent deposition in reservoirs is a universal problem. For the operation of any reservoir, it is required to find out the reservoir sedimentation rate going on in the reservoir. During the last five decades India has constructed several major medium river valley projects involving construction of dams and creation of reservoirs for flood controls. irrigation and hydropower etc.

Present conventional techniques of sediment quantification in a reservoir, like the hydrographic surveys and inflow-outflow methods, are cumbersome, costly and time consuming. With the introduction of remote sensing techniques, it has become very convenient to quantify sedimentation in a reservoir. With the deposition of sediments in the reservoir, the water spread area at an elevation keeps on decreasing. By comparing the decrease in the water spread area with time, the sediment distribution and deposition pattern in a reservoir can be determined indirectly. This information can be used to quantify the rate of reservoir sedimentation.

For the evaluation of sedimentation rate, Bhakra reservoir in Satluj basin has been selected for the present study. The remote sensing data of IRS-1B satellite and LESS-II sensor was acquired for different dates and the water spread areas were extracted. The post-monsoon period of the year 1988-89 and 1996-97 were chosen for the analysis. The original elevation- area-capacity curves and the reservoir levels on the eight dates of pass of satellite were obtained from BBMB, Nangal. Using the trapezoidal formula, the capacity in between the maximum (513.904 m) and minimum (472.232 in) observed levels was obtained for the year 1988-89 and maximum (510.463 m) and minimum (450.436 m) for the year 1996-97. The loss of capacity 491.315 M m3 upto the year 1989-90 and 807.354 M m3 upto the year 1996-97, was attributed to the sediment deposition in the zone of study of the reservoir. The results of this study have been compared with the results of hydrographic survey which was carried out in he year 1988-89.