Simulation of terrain and forest shelter effects on patterns of snow deposition, snowmelt and runoff over a semi-arid mountain catchment

Authors: Marks, Daniel; Winstral, Adam; Seyfried, Mark

Submitted to: Hydrological Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/20/2002
Publication Date: 8/20/2002
Citation: Marks, D.G., Winstral, A.H., and Seyfried, M.S. 2002. Simulation of terrain and forest shelter effects on patterns of snow deposition, snowmelt and runoff over a semi-arid mountain catchment. Hydrological Processes 16:3605-3626.

Interpretive Summary: In mountainous regions, topographic structure and vegetation control patterns of snow deposition, climate conditions, and snowmelt. A snow model was coupled to a wind field and snow redistribution model to simulate the development and melting of the seasonal snowcover over a small mountainous catchment in southwestern Idaho, USA. The catchment was divided into four shelter classes based on terrain and vegetation that were used to assess how the mass and energy balance of the snowcover varies over the basin as a function of terrain and forest characteristics. The wind-exposed areas developed thinner snowcovers and are essentially bare of snow prior to the onset of spring meltout in wind-sheltered areas. The meltout of the wind-sheltered drift and canopy-enclosed regions occurred in conjunction with the springtime increase in solar radiation generating the bulk of springtime runoff. Melt contributions from the drifts may continue into the late spring and early summer providing the only source of water in semi-arid loctions.

Technical Abstract: In mountainous regions, topographic structure and vegetation control patterns of snow deposition, climate conditions, and snowmelt. A topographically distributed snow accumulation and melt model (ISNOBAL) was coupled to a wind field and snow redistribution model to simulate the development and ablation of the seasonal snowcover over a small mountainous catchment, the Reynolds Mountain East basin (0.38 km2) in southwestern Idaho, USA. The model was driven by hourly terrain and canopy corrected data grids derived from meteorological data from two stations located within the catchment for four water years (1986, 1987, 1989 and 1997). In the preceding paper, Winstral and Marks (this issue) detail how terrain and vegetation data were used to distribute station data to simulate snow redistribution and create hourly images of the snowcover energy and mass balance. The catchment was divided into four shelter classes based on terrain and vegetation that were used for an analysis of how the mass and energy balance of the snowcover varies over the basin as a function of terrain and forest characteristics for each of the selected years. As shown by the simulations and verified by detailed point measurements and the late season areal photographs of snow covered area (SCA), in all years the wind-exposed areas developed thinner snowcovers and were essentially bare of snow prior to the onset of spring meltout in wind-sheltered areas. The meltout of the wind-sheltered drift and canopy-enclosed regions occurred in conjunction with the springtime increase in solar radiation generating the bulk of springtime runoff. Melt contributions from the drifts may continue into the late spring and early summer. This research uses a unique set of point and spatial verification data to show that a snow accumulation and ablation model, adjusted for wind redistribution effects, reliably simulated the topographic and vegetation influences on snow distribution, the energy balance, and the hydrology of snow and wind-dominated mountainous regions. Key words: snowcover energy balance, snowmelt, runoff, water resources