Effect of Vegetation on the Accumulation and Melting of Snow at the TW Daniels Experimental Forest

Snow melt is an important component of Western US water resources, accounting for about 50-80% of the annual runoff. Prediction of runoff from snowmelt in heterogeneous watersheds requires the quantification of physical processes accounting for the effects of forest canopy on snow accumulation, melt and sublimation. The forest canopy intercepts snowfall that resulting in smaller snow accumulations in forest area than in open area. The forest canopy also modifies the energy exchange between snow surface and the atmosphere, and alters the sublimation and melting of sub-canopy snow relative to open area. This dissertation has examined ways to improve snowmelt modeling capability to better account for canopy effects and has presented enhancements to an energy balance model that include i) an improved representation of the transmission of radiation through the canopy, ii) an improved representation of the atmospheric transport of heat and water vapor between the snow on the ground, in the canopy and the atmosphere above, and iii) an improved representation of the processes of canopy snow interception and unloading. These enhancements were evaluated against 4 years of field data (2006-2010) collected at the TW Daniels Experimental Forest (TWDEF) located 30 miles N-E of Logan. Observations included continuous automated climate and snow depth measurements supported by periodic field measurements of snow water equivalent and temperature in four different vegetation classes (grass, shrubs, coniferous forest, deciduous forest). The enhanced canopy components were included into the Utah Energy Balance Snowmelt model and provide improved capability to predict the surface water input and runoff from snowmelt in heterogeneous watersheds using a parsimonious approach that can be used with practically available information