Expression of geochemical controls on water quality in Loch Vale, Rocky Mountain National Park

Abstract

Silicate mineral weathering over global scales provides negative feedback to increasing atmospheric CO2 levels through geologic time. There is conclusive evidence of changes in hydrology due to changes in climate from increasing atmospheric CO2; however, only a weak correlation between climate and chemical weathering has been identified in field observations, possibly due to non-linear behavior of geochemical processes or the complex interactions between geochemistry and hydrology in natural systems. For this study, we analyzed concentration-discharge (C-Q) relationships from an 18-year record in a snow-dominated high-alpine watershed to determine geochemical and hydrological processes that control solute concentrations seasonally. In winter months, when discharge from the watershed is low, the system is conceptualized as a batch reactor to estimate rates of chemical weathering from changes in solute concentrations in a stream. We evaluate temporal trends in these data to provide insight into changes in chemical weathering within a catchment over a decadal timescale during modern climate change. This study shows the importance of seasonality in a high alpine watershed, and looks for trends in weathering rates in a transport-limited system on a decadal timescale.