Processes regulating the solute concentrations of snowmelt runoff in two subalpine catchments of the Sierra Nevada, California

Abstract

Geochemical processes regulating solute concentrations in snowmelt runoff were investigated for the snowmelt periods of 1992 and 1993 in two subalpine catchments in Sequoia National Park, California. The catchments, 0.5 and 0.2 ha, have 10 and 25% soil coverage, respectively; the remaining area is exposed granodiorite bedrock. Mineral weathering was the major source of solutes in runoff. Calcium export in excess of stoichiometric plagioclase weathering was attributed to dry deposition and the weathering of mafic minerals and disseminated calcite. Cation exchange was important in the regulation of K and increased base cation export in response to rain-on-snow events and LiBr tracer. Sulfate fluxes were attributed to snowpack elution and SO4 desorption after the beginning of melt. The selective retention of Li during tracer experiments suggests that acid-neutralizing capacity is linked to soil stocks along convoluted flow paths and is not necessarily compromised in areas of sparse soil cover.