The Water Budget of the Kuparuk River Basin, Alaska*

Abstract A water budget study that considers precipitation, river runoff, evapotranspiration, and soil moisture for the Kuparuk River basin on the North Slope of Alaska is presented. Numerical simulations of hydrologic processes using the NASA Catchment-based Land Surface Model are conducted for the period 1991–2001 and provide the partitioning of the observed precipitation input (292 mm yr−1) onto the basin into river discharge (169 mm yr−1), evapotranspiration (127 mm yr−1), and an increase in soil moisture (1 mm yr−1). Discharge attains its annual peak during snowmelt and disposes 58% of the annual precipitation. Evapotranspiration contributes another 43% to the water budget and is mainly associated with warm summertime conditions and a snow-free surface. Combined, surface-snow and blowing-snow sublimation contribute only 5% of the total annual evaporative fluxes. Soil moisture recharge is associated with snowmelt during spring and rainfall during late summer and early fall, whereas soil drying accompanies high evapotranspiration rates during summer. An analysis of interannual variability in the water budget shows that warm, dry years favor a relatively more intense response of river discharge and evapotranspiration to the precipitation input, whereas cool, wet years tend to augment soil moisture.