Discharge Deficits in the Nepali Himalaya Linked to Greening and Warming

Taylor Smith , Bodo Bookhagen

Anthropogenic climate change and rapid infrastructure development have drastically altered the hydrology of many watersheds, influencing the speed at which water is absorbed, stored, and distributed. In this work, we use long-term daily discharge records in the Nepali Himalaya alongside rainfall and snowmelt data to explore whether there have been large-scale shifts in the conversion of upstream water into discharge throughout the region. We find that for the majority of watersheds studied over decadal time scales (~1960s-2015), both rainfall and snowmelt are taking longer to be converted into discharge. We link these changes to increasing water storage deficits, where relatively more surface water is being diverted to soil moisture, vegetation uptake, and deeper water storage reservoirs. We propose that large-scale climate change and vegetation greening have modified catchment-level precipitation-discharge relationships in the Nepali Himalaya.