Title: Investigating how climate change impacts stream hydrologic and geochemical fluxes

Abstract: Quantifying the various ways that climate and land use can alter stream biogeochemistry is critical to managing water resources, yet challenging due to the complexity of critical zone processes, as well as limitations in the spatial and temporal resolution of chemistry data. For example, historic discharge and chemistry trends may not reflect future conditions when the processes that control water storage, transmission, and biogeochemical reactions are fundamentally altered by climate and land use change. Here, we seek to identify hydrologic and biogeochemical processes that are most sensitive to change by comparing watershed discharge and chemistry across variable spatial and temporal scales—from long-term (20+ year) trends from watersheds across the United States using the CAMELS-Chem dataset, to monthly patterns in two mountain watersheds in Colorado. We demonstrate that stream biogeochemistry can shift nonlinearly under two conditions: (1) when hydrologic connection to vertically and laterally distributed solute stores is disrupted, and (2) where perturbation alters biogeochemical reactions. Specifically, we infer changing biogeochemical reactions through the exposure of new reaction fronts, temperature impacts on solubility, and anthropogenic impacts such as acid rain and road salt. Overall, we highlight the complexity of stream biogeochemistry, the importance of long-term data records, and a need to consider the nonstationarity of processes that control how streams accumulate biogeochemical signatures when predicting how climate and land-use impact water quality.

Bio: Sara Warix is an Assistant Professor of Geology and Geophysics at the University of Utah. She received the Editor's Choice Award from Hydrological Processes in February 2024.