The snowmelt-dominated Cascade Mountains provide critical water supply for agriculture, ecosystems, and municipalities. The McKenzie River basin, located in the Central Western Cascades of Oregon, exhibits characteristics typical of many river systems in the western United States. In this watershed farmers, fish, hydropower, and municipal users compete for a limited supply ? especially in summer when in-stream flows reach a minimum. Future climate projections anticipate warmer but wetter winters and longer, drier summers but watershed-scale impacts of these regional projections are not well understood. While snowpack has been measured at the local scale for decades, accurate basin-wide measurements of snowpack do not exist. Recent studies address the effects of climate on the hydrology of the upper reaches of the basin but do not incorporate a basin-wide prediction of snowpack, particularly transient snow at mid-elevations. This presentation will cover a physically based and spatially distributed approach to modeling snow water equivalent at a basin scale. In addition, I will present preliminary results from a binary regression tree approach used to identify the physiographic variables that govern the spatial variability of snow water equivalent in the McKenzie River basin.