Assessment of sedimentation and useful life of Tehri reservoir using integrated approaches of hydrodynamic modelling, satellite remote sensing and empirical curves.

The higher rate of sedimentation in reservoirs is one of the main concerns in sustainable reservoir management, which impairs the functional capacity of reservoirs that may lead to various environmental risks. Estimation of sedimentation rate and useful life of a reservoir using appropriate methods is imperative for sustainable management. This paper deals with the computation of sedimentation rate and useful life of Tehri reservoir of Bhagirathi river, in India, using hydrographic survey analysis, Hydrologic Engineering Center's River Analysis System (HEC-RAS) modelling, satellite remote sensing (SRS) technique, and trap efficiency based empirical curve methods. The rate of sedimentation was found as 5.33 million cubic metres (MCM)/year based on hydrographic survey analysis from the data obtained for the years 2005, 2008 and 2013. Likewise, the mean annual rate of sedimentation was estimated to be 5.07 MCM/year and 5.75 MCM/year based on the HEC-RAS model and SRS techniques respectively. Brune's method and Churchill's method of trap efficiency were found to be inconsistent with the hydrographic survey results. The reservoir can be classified as Type III reservoir with respect to the sediment vertical distribution analysis. Changes in bathymetry obtained in the simulation studies showed that the Bhagirathi river's 28-30 km reach would be most vulnerable to sedimentation problems. The estimated useful life of Tehri reservoir was found to be in the range of 160-180 years. The SRS technique and hydrodynamic model provided a better fit with the observed data. [ABSTRACT FROM AUTHOR]