Land water storage variation over Southern India from space gravimetry

The gravity recovery and climate experiment (GRACE) satellite mission is mapping the earth's gravity field with unprecedented accuracy of a few mu Gal (10(-8) m/s(2)) every month. This provides a new means of studying hydrological, climatic and tectonic processes that redistribute mass, producing temporal gravity changes. Hydrological changes contribute the strongest signal in the GRACE gravity field on seasonal, annual and inter-annual timescales. This communication presents seasonal and annual hydrological signals over India observed by GRACE and compares them with in situ measurements. The spatio-temporal variations of water storage over southern India for 2002-2008 show positive and negative trends, which appear to be related with changes in precipitation patterns. It has also been observed that the negative trend over a large part of south India changed to positive trend after 2005. These observations suggest dominant inter-annual trend of water storage in the southern Indian region. Such observations have also been noticed in the average record of similar to 950 water wells from Andhra Pradesh. We compared GRACE-derived time series with land-based measurements from Andhra Pradesh and found that the GRACE record corroborates with ground data, implying its application in the monitoring of water storage in the region.