CS(AR)-2/2006-07 : Streamflow modelling of Bhagirathi river : Hydrograph separation using isotopic and geochemical techniques

Abstract

The three important river systems originating from the Himalayan region are: the Indus, the Ganges and the Brahamaputra. Excluding Brahamaputra and Indus, which flow parallel to northern range of Greater Himalayas, towards west and east respectively, all other remaining rivers including few tributaries of Brahamaputra and Indus cut across the Himalayas and flow from north to south. The River Ganga, one of the major rivers of Himalayas originates from the Gangotri Glacier. Importance of the River Ganga in the Indian context is better understood from the fact that it continues to play a major role in the socio-economic development of the entire northern part of the country. The dependency of Uttaranchal, Uttar Pradesh, and other lower riparian states on the water resources of Ganga River for the sustenance and growth of agricultural and hydroelectric power sector is ever growing. River Ganga receives significant contribution from snow and glacier melt through Bhagirathi and Alaknanda rivers, main tributaries of river Ganga, originates in Higher Himalayas. During the lean flow period in summer, the snow and glacier melt remains important for drinking and irrigation purpose and for the sustenance of hydroelectric projects. It is therefore required to carry out the scientific studies to estimate the contribution of snow and glacier melt, subsurface and surface - runoff component of Ganga River in upper reaches (i.e., Bhagiathi River and Alaknanda).

BRNS, DAE, Govt. of India, Mumbai funded the present project to NIH for hydrograph separation in order to understand the contribution of different component in Bhagirathi river using isotopic and geochemical techniques and flow modeling. Isotopic signatures of different component such as precipitation, snow/ glacier melt, subsurface flow, surface runoff were developed by collecting representative water sample of each category. NIH collected the hydrological and meteorological data from CWC and other field agencies. Along with the isotopic models, SNOWMOD and ANN modelling were applied to cross check the results of isotopic investigations.

The project activities were planned under the guidance of Dr. Bhishm Kumar Scientist F and Head, Hydrological Investigations Division and executed by Dr S. P.Rai, Scientist El Hydrological Investigations Division at NIH. Dr. Noble Jacob Isotope Hydrology Section, Isotope Applications Division, Bhabha Atomic Research Center, Trombay, Mumbai played the role of Principal Coordinator of the project. Dr Sanjay Jain Scientist E II, Surface Water Hydrology Division carried out stream flow modeling using SNOWMOD model and Shri Senthil Kumar Scientist El Surface Water Hydrology Division developed ANN model. The other scientists of the Institute who have been actively involved during the project include Shri S. K. Verma, Scientist C and Shri Pankaj Garg Scientist B and extended their help in sample collection. The laboratory analysis stable isotopes were carried out by Shri Jamil Ahmad SRA, Shri Vipin Agrawal, SRA and Vishal Gupta, RA. In addition to this, Sh. Y. S. Rawat, Project Officer appointed under the project, also assisted in the field work and preparation of the report. I hope that the results of the project would be very much useful for the sustainable development and management of the water resources projects in the Himalayan region in general and for the Bhagirathi/Ganga River Basin in particular. However, there is a need to carry out the long-term studies which will enhance the knowledge about the melting pattern of the Himalayan glaciers and provide the capabilities of the hydrological models for simulating the runoff within the desirable accuracy.