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Relationships between Snow Cover and Winter Losses of Dissolved Substances from a Mountain Watershed
William M. Lewis, Jr. and Michael C. Grant
Arctic and Alpine Research
Vol. 12, No. 1 (Feb., 1980), pp. 11-17
Published by: INSTAAR, University of Colorado
Stable URL: http://www.jstor.org/stable/1550586
Page Count: 7
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The yield of dissolved materials from a mountain watershed at 2900 m elevation near the Continental Divide in Colorado 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 first year, low the second year, and higher than normal the third year. Under a substantial snow cover, the ground surface typically remains unfrozen, whereas bare areas freeze all the way to bedrock. The variation in snowpack thus implies considerable variation in soil frost. The yield of dissolved materials was significantly different between years for Ca++, Mg++, K+, PO4-P, NO3-N, Dissolved Organic Phosphorus, HCO3 - and H+. There were no significant differences between years (P > 0.05) for SO4 --, Na+, NO2-N, NH4-N, Dissolved Organic Carbon, and Dissolved Organic Nitrogen. 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 effect of low snowpack and the associated extensive soil frost on losses of nitrate from the system is much more extreme than for any of the other dissolved constituents. Exports of nitrate were approximately tripled in the year of minimum snowpack and maximum soil frost. The response of biologically active substances such as phosphate and potassium is generally higher than the response of other substances which are not in such great biological demand, suggesting that 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.