Streams, sewage, and shallow groundwater: stream-aquifer interactions in the Kathmandu Valley, Nepal

Abstract The Kathmandu Valley in Nepal is facing a water quantity and quality crisis due to rapid urbanization haphazard wastewater planning management. Annually, groundwater extractions the exceed capture, resulting table declines. Streams are often important sources of recharge (or destination discharges from) aquifers. However, stream-aquifer interactions poorly understood. To improve this understanding, we performed topographic surveys levels, measured quality, streams adjacent hand-dug wells (shallow aquifer). In pre-monsoon, 12% (2018) 44% (2019) had levels higher than streams, indicating mostly loss stream aquifer. post-monsoon, 69% 70% that monsoon rainfall contributes shallow aquifer which, at least temporarily, causes transition from losing gaining. Concentrations all parameters (electrical conductivity, ammonia, alkalinity, hardness) were pre-monsoon compared post-monsoon both wells. There was no recurring trend level difference longitudinally upstream downstream. depleted While clearly observed seasonal refilling aquifer, role deep storage processes deserve future research attention.