Relationships between Snow Cover and Winter Losses of Dissolved Substances from a Mountain Watershed

Abstract

The yield of dissolved materials from a mountain watershed at 2900 m elevation near the Continental Divide in Colorado [USA] was computed for 3 yr with very different snowpack conditions. The analysis focuses on the loss of materials during the low-flow season, which extends from fall prior to snow cover through winter. Snowpack was normal the 1st yr, low the 2nd yr and higher than normal the 3rd yr. Under a substantial snow cover, the ground surface typically remains unfrozen; bare areas freeze all the way to bedrock. The variation in snowpack implies considerable variation in soil frost. Substances the yields of which differed significantly between years always showed a strong tendency for yield to be negatively related to the amount of snow cover. In the comparison between years, statistical corrections were made for discharge, so the differences between years must be largely explained by factors related to snow cover, of which soil frost is the most obvious. The response of biologically active substances such as phosphate and K is generally higher than the response of other substances which are not in such great biological demand; apparently, soil frost increases the yield of substances from the watershed by interfering with biological sequestering mechanisms which would ordinarily trap these substances in the terrestrial system.