Abating water storage and associated hydrological processes in Indian Himalayan river basins

Abstract

In recent decades, the hydrological balance/budget over Himalayan river basins has imperatively become crucial for decision-making in flood risk, water resource management, identifying water-sensitive areas etc. In the present study, assessment of the abating total water storage (TWS) in the three river basins viz. Indus (IRB), Ganga (GRB) and Brahmaputra (BRB) is carried out. TWS contributory factors, viz. precipitation, evaporation, runoff, snow water equivalent (SWE), soil moisture, groundwater etc., are arguably assessed. TWS anomaly and other variables are considered, and corresponding statistical seasonal (winter, premonsoon, monsoon and postmonsoon) trends are calculated using the Mann–Kendall test and the Theil-Sen estimator. Dominant monsoon precipitation over GRB and BRB and winter precipitation over IRB contribute to the replenishment of TWS with almost a month lag. Still, there are decreasing TWS trends. Most of the basins are drying, though slower during monsoon. Maximum decrease in TWS is observed in postmonsoon over IRB, while GRB and BRB show it in premonsoon. The highest intraseasonal variability is shown by precipitation, followed by runoff. Evaporation shows less variability and is less dependent. Present work will be of utmost importance for the policy or planning for governance at the state level for societal benefit.