Assessing groundwater recharge in arid and semiarid regions using integrated modeling and remote sensing

Accurate evaluation of groundwater recharge in arid and semi-arid environments is crucial to make reasonable decisions in water resources management. Groundwater recharge is a complex function of factors including precipitation, irrigation, soil type, vegetation, geology, and hydrogeological conditions. Significant efforts have been made to develop methods for measuring or calculating recharge rates, such as direct measurement, water budget, Darcyan model, and tracer. However, estimating recharge at a regional scale remained challenging as above-mentioned factors vary spatially and temporally. In this study, we assessing disturbed groundwater recharge for the Indus River Basin using integrated groundwater surface-water modeling and remote sensing data. Our study domain is located in arid and semiarid region, it has the world's largest irrigation system. Groundwater provides ~ 35% of the basin's overall water supply, of which ~ 94% is for irrigated agriculture. The very limited precipitation of ~365mm annually and irrigation return composed main sources of ground water recharge. We estimated the return flow from runoff and irrigation accounting influences of land cover land use and their change. We compared the simulations of physical modeling accounting for subsurface heterogeneity. We projected the scenarios of different crop patterns and irrigation schemes. The groundwater recharge estimates from our approach are compared to the current estimates from water balance approach. Results show that we need to improve our understanding of present conditions and be aware of the impact of human interventions to groundwater flow system. Our research results present the feasibility and value of combined modeling and remote sensing approach to support sustainable water resource management for heavily stressed aquifers.