Major Ion Chemistry and Sensitivity to Acid Precipitation of Sierra Nevada Lakes

Most alpine and subalpine lakes of the Sierra Nevada (California) are very dilute, weakly buffered calcium bicarbonate waters. Seventy‐three lakes selected to lie in basins representative of Sierran bedrocks were sampled in the summers of 1981 and 1982 and have a median alkalinity of 50 μeq 1 −1 (range 5–1137) and a p H of 7 (range 5.7–9.4). The alkalinity of Sierran lakes cannot be predicted from altitude, basin area, or lake area. The concentrations of sulfate, calcium, or alkalinity in lake waters are positively correlated with the percent areal coverage of volcanic or calcareous rocks in the basins. The lakes are not acidified but are extremely sensitive to increases in acidity of atmospheric precipitation.