Reservoir Capacity and Sedimentation Assessment by Integrating Echo Sounding and Remote Sensing Techniques

Periodical assessment of reservoir capacity and sedimentation is inevitable to safeguard and sustain the reservoir life. Under the changing climate, it is predicted that high-intensity rainfalls in the catchment areas will elevate the sediment and nutrient influx into the reservoir. In this study, the use of integrated methods in estimating the reservoir capacity of a multi-purpose Krishnagiri reservoir, in Ponnaiyar basin, India is demonstrated. Single beam dual frequency eco-sounder and temporal satellite imageries were used to estimate the reservoir capacity. A bathymetry survey was conducted when the reservoir was at 480.20 m against the 483.11 m Full Reservoir Level (FRL). Sentinel 2 images are captured and analysed for the water spread areas between 480.20 and FRL. The total reservoir capacity (34.81 MCM) is estimated as the sum of the volume obtained by the bathymetry survey (11.11 MCM) and the volume obtained by remote sensing techniques (23.7 MCM). It is found that 100,000 m³ of soft sediments are deposited in the mid portion and along the dam structure. Around 49% of storage capacity has decreased since the commissioning of the dam. There is environmental degradation at the catchment scale which needs to be addressed immediately by adopting suitable soil and water conservation measures to sustain the life of the reservoir.