A new model is being developed to describe the water and energy balance of small mountainous catchments that are subject to snow accumulation and snow melt. Catchment topography parameters are determined from a digital elevation model. Distributed water storage capacity is calculated by combining depth-to-bedrock data with soil porosity data. At the surface, the complete energy balance is calculated using standard meteorological input. The snowpack, if present, is represented by two main state variables: water equivalence and energy content (similar to the Utah Energy Balance Snow Accumulation and Melt Model). Lateral subsurface flow above the bedrock is calculated using the Boussinesq equation. Saturation-excess surface runoff is moved to neighboring cells assuming instantaneous redistribution. The model is tested in the Boise-Front Experimental Watershed, Boise, Idaho.