Analysis of Surface Sediment at Tropical Freshwater Lake Using SONAR System with Field Validation

Freshwater management is increasingly becoming more and more critical to human well-being and sustainable socio-economic development. Due to siltation, reservoir storage capacity is decreasing, especially in tropical areas where the monsoon season is concentrated in the first 3 months of the year requiring continuous desiltation efforts. The desiltation efforts require precise knowledge of the sediment type and the siltation pattern. An acoustic means for sediment classification have a distinct advantage over the popular remote sensing techniques due to inherent accuracy and all weather availability. The analysis of surface sediment and deep layer sediment is essential for the selection of appropriate dredging instruments. Therefore, the objective of the current work is to perform the sediment analysis of the Khadakwasla Lake using acoustic approach which serves as guidance for decision-makers for de-siltation planning. Hence, in the present study, the surface sediment characterisation in Khadakwasla Lake situated at Pune, Maharashtra, India has been performed and it is validated with energy and central frequency shift models. An experiment uses in this study is Edge-Tech SB216S sub-bottom profiler for data collection. The surface sediment reflection coefficients obtained from the energy model are in the range from 0.06 to 0.18, indicating the presence of clay, clay silt and silty clay. The center frequency shift attribute used in the relaxation time model proved to be more reliable for deep layer sediment morphology. The results showed that the center frequency shift is up to 25 Hz, indicating that the survey region is crowded with clay, fine to coarse silt. This study is first of its kind in Maharashtra, India which will help desiltation efforts in tropical lakes.