Strong influence of groundwater pumping on streamflow depletion across North India

Abstract

The world’s largest freshwater resource - groundwater is essential for irrigation and food security. However, unsustainable groundwater pumping, exceeding recharge from precipitation, has led to significant groundwater depletion, particularly in intensively irrigated regions like north India, with cascading impacts on streamflow. Groundwater storage losses reduce groundwater discharge to streams, reverse flow directions, or cease discharge entirely, thereby reducing streamflow. Despite its critical implications on water security, ecosystem health, and agricultural sustainability, the relative influence of groundwater pumping and climate variability in driving streamflow variability remains poorly understood. Most previous studies often relied on coarse-resolution models that overlook groundwater-surface water interactions and lateral groundwater flow. To address these limitations, we applied the physically based, integrated land surface-groundwater model ParFlow-CLM at a 5 km resolution from 1970 to 2022 across the Ganga and the Indus basins. This physically based model simulates three-dimensional groundwater flow using the Richards equation and couples it with land surface processes, enabling robust analysis of groundwater-streamflow interactions. We find that streamflow variability in north India is primarily driven by groundwater abstraction for irrigation, modulated by precipitation variability. Excessive pumping has shifted streams from gaining groundwater to losing it, approaching critical environmental flow thresholds. The study underscores that prolonged groundwater pumping has significantly reduced baseflow contributions, which has critical implications for water management in India.