SPATIO-TEMPORAL ANALYSIS OF SEDIMENTATION IN INDIRA SAGAR RESERVOIR: A CASE STUDY

Abstract

Dams and reservoirs are among the world‘s most important and largest infrastructures created across the world. They are an important source of reliable water storage which can be released at different time intervals as per the need and requirement. They serve varied purposes like hydropower generation, irrigation, domestic and industrial demands. However, due to the various reasons like ageing of dams, lack of proper upkeep and maintenance, absence or faulty sediment management strategies, catchment degradation through deforestation, selection of dam site without considering the sediment transport/ deposition and river morphology etc., the problem of sedimentation in reservoirs is increasing at a pacing rate. This negatively impacts the reliability of water supply for the various purposes for which the dam is constructed. This sediment may also reduce the efficiency of hydropower plant through clogging and cause corrosion of turbines. Hence, it is important that the amount of sedimentation occurring in reservoirs be monitored regularly and accordingly, the sediment management practices be adopted. Planning of suitable measures requires identification of source of erosion and its quantification, so that sustainable targeted interventions may be planned and timely action taken. In this study, it has been attempted to estimate the change in the water spread area of Indira Sagar Reservoir using tools like Google Earth Engine and Remote Sensing. Soil erosion map of the area upstream of the Indira Sagar Reservoir is made using the RUSLE model. Sentinel 2A data was used to delimit the spread of water in reservoir for the years 2016, 2020 and 2021. Water pixels were identified and area extracted using Normalized Difference Water Index (NDWI), which is further utilized to determine the difference in reservoir storage capacity. A loss of 2.94% has been estimated in the capacity of reservoir within a span of 5 years (2016-2021). Most of the area in the upstream of the study region is found to be slight to moderately eroded. This study may prove very helpful to the water planners for sustainable planning and development of water resources projects.