An analysis of spatio-temporal variability of terrestrial water storage in India

Terrestrial water storage (TWS) accounts for the largest temporal variation in Earth’s gravity field on contemporary time scale. The time-variable gravity observations for from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have been extensively used to estimate TWS variations and supplement the sparse in-situ hydrological observations. We use multivariate statistical tools over gridded time series of monthly TWS for an assessment of dominant regional variability and to identify seasonal, inter-annual and linear trends of TWS over India. The analyses recognize seasonal variability of TWS corresponding to rainfall over India and detect two contrasting (positive and negative) regional trends, which are compared with hydro-climatic variables for attributing underlying potential causes. These analyses suggest the probable causes of TWS variations over the different regions of India, like role of reservoirs in central and southern India for increase of TWS and groundwater pumping in northern India for TWS decline.