EVALUATION OF THE EFFECTIVENESS OF TEMPERATURE-INDEX AND ENERGY BALANCE SNOW MODELS FOR HYDROLOGIC SIMULATION OF A MOUNTAIN CATCHMENT

In the western North America, snow plays an important role in regional hydrology by storing water during winter for later release during melt. This natural storage reservoir has become the central component of western water management. It acts as a buffer against winter flooding, and supplies critical water in a timely manner for hydropower generation and for domestic and agricultural water use during the dry spring and summer growing season. We apply the Pennsylvania State Integrated Hydrology Model (PIHM) over a well-instrumented headwater mountain catchment within the Reynolds Creek Experimental Watershed (RCEW) in the Owhyee Mountains of Idaho. Simulations were conducted for a series of wet and dry years from 1984 to 2008, using both a temperature-index and an energy balance approach to modeling the snowcover. We use these to compare how reliably each method predicts snow distribution and melt, patterns of soil moisture, and timing and magnitude of streamflow under a range of hydroclimatic conditions. The specific focus is rain-on-snow (ROS) events, which many times lead to mid-winter flooding, and are more likely to occur under warmer climate conditions. Because the energetics of ROS are determined by sensible and latent heat flux at the snow surface, the impact of a specific event depends on wind, antecedent conditions, and the state and distribution of the snow cover. This work will lead to improved modeling strategies that will be effective in a changing climate.