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USGS · 70018841

Composition of precipitation, bulk deposition, and runoff at a granitic bedrock catchment in the Loch Vale watershed, Colorado, USA

David W. Clow·M. Alisa Mast
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Abstract

The chemical composition of precipitation, bulk deposition, and runoff from a 30-m2 granitic bedrock catchment in the Loch Vale Watershed in Rocky Mountain National Park was monitored over a 6-week period in the summer of 1994 to determine the importance of dry deposition in the alpine zone. Concentrations of acid anions and base cations were 1.1 to 4 times higher in bulk deposition than in precipitation. Concentrations of the same solutes were 3 to 10 times higher in runoff from the bedrock catchment than in bulk deposition, and during individual runoff events, the concentrations of most ions were highest in the initial runoff. Evaporation from the rock surface accounted for only a 15% increase in solute concentrations indicating that most of the dissolved load in bedrock runoff is derived from the dissolution of dry deposition that accumulates on the bedrock between storm events. These results indicate that dry deposition may be an important source of solutes to this alpine ecosystem.

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Biogeochemistry of seasonally snow-covered catchments. Proc. symposium, Boulder, 1995Article

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David W. Clow, M. Alisa Mast. 1995. Composition of precipitation, bulk deposition, and runoff at a granitic bedrock catchment in the Loch Vale watershed, Colorado, USA. https://pubs.usgs.gov/publication/70018841

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USGS1995

Chemical and isotopic evolution of a layered eastern U.S. snowpack and its relation to stream-water composition

The chemical, isotopic, and morphologic evolution of a layered snowpack was investigated during the winter of 1993-94 at Sleepers River Research Watershed in Danville, Vermont. The snowpack was monitored at two small basins: a forested basin at 525 m elevation, and an agricultural basin at 292 m elevation. At each site, the snowpack morphology was characterized and individual layers were sampled seven times during the season. Nitrate and 8d18O profiles in the snowpack remained relatively stable until peak accumulation in mid-March, except near the snow surface, where rain-on-snow events caused water and nitrate movement down to impeding ice layers. Subsequently, water and nitrate moved more readily through the ripening snowpack. As the snowpack evolved, combined processes of preferential ion elution, isotopic fractionation, and infiltration of isotopically heavy rainfall caused the pack to become depleted in solutes and isotopically enriched. The release of nitrate and isotopically depleted water was reflected in patterns of nitrate concentrations and ??18O of meltwater and stream water. Results supported data from the previous year which suggested that streamflow in the forested basin during snowmelt was dominated by groundwater discharge.

Biogeochemistry of seasonally snow-covered catchme↗