Removal of nitrogen from snowmelt water by the soil-vegetation system, Lake Tahoe basin, California

Most of the precipitation in the Lake Tahoe basin falls as snow between October and May. Fresh snow usually contains concentrations of inorganic and organic nitrogen that far exceed those found in highly oligotrophic Lake Tahoe. Algal productivity in the lake is most sensitive to additions of the nutrient ion, nitrate. Research by the Tahoe Research Group in the Ward Valley watershed near Tahoe City has revealed that over 80% of the nitrate-nitrogen in the snowpack is removed by the natural soil-vegetaton system prior to the entry of melt water into the stream and lake. Soil disturbance and vegetation removal can severely damage the effectiveness of the nitrogen removal process. Construction practices in this subalpine environment should be carefully controlled to minimize destruction of the natural protective cover on sensitive sites. We are attempting to identify such sites and to evaluate the impact of development on nitrate release to the aquatic sysem.