Surface energy balance changes impact on hydrometeorological variables over Indus-Ganga-Brahmaputra

Abstract

Over the past decades, the estimation of changes in climate and energy mass balance of Earth’s surface has become crucial. The Himalayas, in the South Asian region, are highly vulnerable to precipitation and hydrological/hydrometeorological balance/change. It will significantly affect freshwater availability and the associated sectors of these habitats. The understanding of these changes in hydrological balance for water resource management; identifying the water-sensitive areas; etc. over three major Himalayan river basins, Indus-Ganga-Brahmaputra (IGB), are considered. The geomorphological features, seasonal variability, topographic and geographical differences, landuse/landcover heterogeneity, etc. are distinctly different among them. These in conjugate interaction with above atmosphere induce different feedback mechanisms and processes. Precipitation, turbulent fluxes, evaporation, potential evaporation etc., are considered to assess surface energy balance and different thermodynamical processes. Nonparametric Mann-Kendall method for trend analysis, while the Pettit test for change point detection is employed over data period of 1950–2020. Based on the change point year 1981, the difference in mean precipitation between the periods 1982–2020 and 1950–1981 shows a decreased during monsoon and post-monsoon over GRB and BRB. Interestingly, the change years of potential evaporation and evaporation are highly correlated with monsoon in BRB while the same is weak for GRB. It shows the impact of land use type of the two basins where BRB has more forest cover than of GRB. A lead-lag relationship between the Bowen ratio and different hydrometeorology variables is seen. Present results on changes are important and will be useful for planning and policy for societal benefit viz., better water resource management, potential impacts due to climate change, etc. This study helps policymakers in better understanding of the changing precipitation pattern which will help in formulation of new policies for agriculture and sustainable use of water resources.