The effect of basin physiography on the spatial distribution of snow water equivalent and snow density near peak accumulation by Karl Bruno Wetlaufer.
Wetlaufer, Karl Bruno
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This study quantifies the effect of the physiography (elevation, potential incoming solar radiation, land cover, etc.) of a large (207 km 2) and complex mountainous basin on the spatial distribution of snow water equivalence (SWE) and snow density during peak SWE accumulation. SWE and snow density were sampled in areas of the basin that were physiographically representative (based on unique combinations of elevation, incoming solar radiation, and land cover) to the basin as a whole. Sampling took place over a variety of spatial scales (10m-400m) in a semi-random and structured manner acquiring over 1,000 direct measurements of SWE and snow density. Three modeling approaches were used in the analysis of the SWE data; regression tree, conditional inference tree, and mixed effects multiple regression. The three modeling approaches were similar in their estimates of total basin SWE (approximately within 1% of their averages) but provided very different patterns of how SWE is spatially distributed throughout the basin. All three methods showed elevation and potential incoming solar radiation to have the most significant influence on the spatial distribution of SWE, with land cover also being significant in the mixed effects and conditional inference tree models. Snow density was observed to vary widely throughout the basin with a standard deviation of 61 kg/m 3 around a mean of 349 kg/m 3. The spatial distribution of density was modeled using regression tree and multiple linear regression analysis. Both models estimated similar basin average snow density using elevation and radiation as explanatory variables, but displayed considerably different spatial distributions and ranges of value. This study demonstrates the importance of elevation and radiation for modeling the spatial distribution of SWE and snow density in a large and physiographically diverse basin and expresses the differences that exist between various methods of modeling these phenomena.