Observed changes in surface water availability in the Indian sub-continental River basins

Abstract:

We examined long-term (1901-2012) changes in the hydroclimatic variables in the 18 Indian sub-continental basins. Between 1950 and 2012, a significant decline in the monsoon season (June to September) precipitation, evapotranspiration (ET), and total runoff was observed in many sub-continental river basins that are key to water availability in the one of the most populated regions (e.g. Central India) in the world. On the other hand, significant increases in precipitation, ET, and total runoff were noticed in majority of the basins during the period of 1901-1949, which highlight a diametric nature in changes in the surface water availability. The central Indian region where the changes in surface water availability were more prominent experienced an increase (decline) of 19 (-8) % in total runoff and 8 (-6) % in ET during the pre (post) 1950 periods. While the Ganges, Brahmaputra, Mahanadi, Narmada, and Godavari river basins experienced declines in the monsoon season precipitation, ET, and total runoff, a significant increase in air temperature was noticed in 15 out of 18 sub-continental basins during the period of 1950-2012. Sea surface temperature (SST) in the Indian Ocean increased more than 1.0ºC during the period of 1950-2012, which is strongly associated with the declining trends in surface water availability in the sub-continental river basins. Moreover, SST variability in the Indian Ocean is associated with the diametric changes during the pre and post-1950 in water availability in the central India.