Analysis of sediment and discharge ratings of Ganga River, India

Abstract

Design, operation and management of dams and reservoirs is governed by the discharge and sediment load and of a river. Despite being among the largest river basins in the world, sediment–discharge ratings of the Ganga River has received little attention from the researchers probably due to lack of data availability. The present paper aims at analysing the sediment and discharge rating characteristics at 15 gauging stations of the Ganga River. Significant scatter exists in the sediment–discharge relationship during monsoon season and as such a single rating curve was not found adequate to define the sediment–discharge relationship. To address the scatter in sediment–discharge relationship, a novel monthly index number was introduced in sediment–discharge rating curve equation. The rating equation parameters were estimated using a generalized reduced gradient (GRG) solver available in MATLAB. Qualitative as well as quantitative comparison of single rating curves with monthly sediment rating curves reveal that monthly sediment rating curves were in better agreement with the observed data as compared to the single rating curve. Significant spatiotemporal variation in sediment and discharge and inverse correlation between sediment rating parameters exist in the Ganga River. It was also observed that the scatter in stage–discharge relationship was less as compared to the sediment–discharge relationship. No consistent relationship could be found between rating curve parameters and the magnitude of discharge or season. The concept of index number can be applied to other rivers where significant monthly or seasonal scatter in sediment–discharge relationship exist. © 2021, Saudi Society for Geosciences.