Comparison of Snow Deposition, the Snow Cover Energy Balance, and Snowmelt at Two Sites in a Semiarid Mountain Basin

Abstract

Significant differences in snow deposition, development of the seasonal snow cover, and the timing of melt can occur over small spatial distances because of differences in topographically controlled wind exposure and canopy cover. To capture important intrabasin hydrological processes related to heterogeneous snow cover and energy inputs, models must explicitly account for these differences. The ?SNOBAL? point snow cover energy and mass balance model is used to evaluate differences in snow cover energy and mass balance at two sites in a small headwater drainage of the Reynolds Creek Experimental Watershed (RCEW) in the Owyhee Mountains of southwestern Idaho. Though these sites are separated by only 350 m, they are located in distinctly different snow cover regimes. The ?ridge? site (elevation 2097 m) is located on a broad shelf on the southern ridge of RCEW, and the ?grove? site (elevation 2061 m) is sheltered by topography and forest canopy in a grove of aspen and fir trees just in the lee of the ridge on which the ridge site is located. Precipitation and climate data from these sites were used to drive SNOBAL for three water years: the 1984 water year, the largest discharge year on record; the 1992 water year, the smallest discharge year on record; and the very windy 1999 water year. Simulated energy balance during meltout at the ridge site was dominated by sensible heat flux; at the grove site the primary energy input during meltout was net allwave radiation. Comparison of total annual snowmelt with measured stream discharge from this headwater drainage showed that neither site adequately represented the basin input of water in any of the model years. This analysis details the disparity in energy and mass fluxes during the snow accumulation and ablation cycle between two proximal sites, illustrating the importance of understanding and spatially accounting for variable energy inputs and snow deposition patterns.