Land water storage variation over Southern India from space gravimetry

Abstract

Gravity Recovery and Climatic Experiment (GRACE) satellite is mapping earth’s gravity field with unprecedented accuracy of few micro-Gals every month. This provides vast prospects of studying hydrological, climatic and tectonic processes that redistribute mass, producing temporal gravity changes. Hydrological changes contribute strongest signal in the GRACE gravity field on a seasonal, annual and inter-annual scale. This paper presents, GRACE captured seasonal and annual hydrological signals over India and compare them with in-situ measurements. The spatio-temporal variations of water storage over southern Indian region for 2002-2008, show positive and negative trends both due to the changes in precipitation. Some parts of southern India covering Kerala and Tamilnadu consistently show a negative trend of water storage that partly coincides with over exploited areas reported by CGWB based on long period ground data and thus need a management programme for sustainable water development for these region. Our analyses demonstrate the usefulness of utilizing satellite gravity observations for studying variation of water storage over a region of areal extent similar to individual states or basins.