A Physically Based Daily Simulation of the Glacier-Dominated Hydrology of the Copper River Basin, Alaska

The large, highly glacierized Copper River basin is an important water resource for the south-central region of Alaska. Thus, information is needed on the reaction of its hydrologic timing and streamflow volumes to historical changes in climate, in order to assess the possible impact of future changes. However, the basin is remote, and therefore, it has proved difficult to collect field data in a frequent temporal and spatial manner. An extension of the distributed-parameter, physical-process code Precipitation Runoff Modeling System, PRMSglacier, has been specifically developed to simulate daily hydrology without requiring extensive input data. In this study, PRMSglacier was used to characterize the hydrology of the Copper River basin from 1959 to 2015. The basin was split into subbasins for specific regional climatic calibrations and finer resolution characterization. The model was calibrated and performed well against data of glacier mass balance, glacier area change, snow cover, gaged streamflow, evapotranspiration, and solar radiation. Ice melt contributed 26% of the total basin streamflow, with differences temporally from climate oscillations. Furthermore, differences were seen geographically in subbasins depending on the state of the glaciers in each subbasin. Decreasing trends in ice melt volume were mostly seen on smaller steeper glaciers responding to a critical level of glacier recession, while increasing trends in ice melt volume were mostly seen on larger valley glaciers responding to increasing temperature. The areas with substantially decreasing ice melt had decreasing streamflow, possibly indicating health concerns for the ecosystems therein.