Morphometric and hydrological study of Alaknanda and Bhagirathi basins

Abstract

The river Ganges has its practical origin from the confluence point of its two tributaries the Alaknanda and Bhagirathi at a place known as Devprayag. These two rivers have their own very large catchments or drainage basin. Both of them have their own drainage characteristics in terms of physical area and ecological habitats. The variability of discharge from both the catchments determines the flow regime in the river Ganga. The international nature of river Ganga and its huge basin makes its study complicated and its hydrological data difficult to obtain. For the sake of studying the flood behavior downstream in period of emergency like that in 2013 Uttarakhand tragedy, an indirect approach is to obtain the flow regime through morphometry. The various novel and traditional approaches gives us a unique opportunity to predict the flow regime in 30 year to more than 100 year return period flood conditions. In this study the DEM of ASTER and SRTM have been utilized to analyze morphometry using D-8 method. The drainage basin shape, area, perimeter, density, river network, river length, vertical distances, slope, hypsometric curves and longitudinal profiles are calculated for both the basins using both ASTER DEM of 30m and SRTM DEM of 90m resolution. Further using empirical equations an attempt is made to calculate discharge at outlet point for both the basins. This is correlated statistically with different morphometric parameters to know which factors are best representing the basin flow regime of the basins.