ASSESSMENT OF RESERVOIR SEDIMENTATION USING REMOTE SENSING DATA

Abstract

Periodic evaluation of sediment deposition pattern and the assessment of available live storage capacity in a reservoir are an integral component of the optimum water resources management. The conventional techniques of sedimentation quantification in a reservoir, like the hydrographic surveys and inflow-outflow methods, are cumbersome, costly and time consuming. Further, prediction of sediment deposition profiles using empirical and numerical methods requires large amount of data and the results are still not accurate. Remote sensing, through its spatial, spectral and temporal attributes, can provide synoptic, repetitive and timely information regarding the revised water spread area in a reservoir. By using the digital analysis techniques and the geographic information system in conjunction, the temporal change in water spread area is analysed to evaluate the sediment deposition pattern in a reservoir. In the present study, the data of IRS-1B LISS-III sensor is used and the analysis is performed on the ERDAS/IMAGINE 8.6 system for assessment of reservoir sedimentation in Ramganga catchment. The investigation of basins for planning soil conservation requires a selective approach to identify smaller hydrological units, which would be suitable for more efficient and targeted conservation management programmes. One criterion, generally used to determine the vulnerability of catchments to erosion, is the sediment yield of a basin. In India, sediment yield data are generally not collected for smaller sub-catchments and it becomes difficult to identify the most vulnerable areas for erosion that can be treated on a. priority basis. An index-based approach, based on the surface factors mainly responsible for soil erosion, is suggested in this study. These factors include slope, landuse, brightness and greeneness. etc. The catchment is divided into 9 sub-watersheds, and iii topography related parameters are estimated separately for each sub-watershed. Satellite data are used to evaluate the water index, while a GIS system is used to evaluate the topography and morphology-related indices. The integrated effect of all the parameters is evaluated to find different areas vulnerable to soil erosion. One sub-watersheds is identified as being most susceptible to soil erosion. Based on the integrated index, a priority rating of the watersheds for soil conservation planning is recommended.