Estimation of Terrestrial Water Storage change in the Bhagirathi Ganga and Vishnu Ganga basins using satellite gravimetry

Terrestrial Water Storage (TWS) in the Bhagirathi Ganga and Vishnu Ganga basins is an important hydrologic component for the Ganga River. Improved estimation of TWS in the Bhagirathi Ganga and Vishnu Ganga basins is crucial for water resources management for India. Despite its importance, storage and change of TWS in the study area has not been well studied at a larger scale. In this investigation, TWS and its change (TWSC) is estimated in the Bhagirathi Ganga and Vishnu Ganga basins during the period of 2004 to 2010. TWS is calculated from two methods: The first method employs the GRACE remote sensing satellite while the second employs estimation by use of climate data of study area provided by NOAA. TWSC is estimated from the TWS by subtraction of two consecutive monthly values. In addition, Total water storage change is also estimated from a water balance approach using a combination of precipitation, runoff and transevaporation. The spatial average values of GRACE and NOAA from 1°×1° spatial resolutions was extracted using a watershed mask derived from the DEM of the Bhagirathi Ganga and Vishnu Ganga basins. The TWS result from the GRACE and NOAA show decreasing trend in TWS of 0.54 cm/year and 0.2 cm/year, respectively due to decrease in precipitation, high evaporation of the study area. The results indicate the great potential of GRACE and water balance approach using NOAA data for providing hydrological information to water resource management in Uttarakhand.