Drivers of Solute Concentration Across the Continental United States

State factors and landscape characteristics are a driving influence for multiple ecosystem processes and consequently control dissolved nutrient concentrations in streams and rivers. Understanding the controls on solute concentrations has major implications for environmental sustainability including water quality, forest productivity, greenhouse gas production, and predictive models of solute export to downstream ecosystems. To better understand how solute concentrations respond to gradients in lithology, soil type, topography, vegetation, and climate, we compiled multiple continental-scale data sets (e.g. CAMELS, USGS NWIS) to integrate stream water chemistry data with broad gradients of landscape and climatic characteristics. The data set includes greater than 2200 chemistry measurements among 671 streams and rivers spanning the continental United States. Each site is paired with 50 landscape, geologic, climatic, and soil characteristics. We use Structural Equation Modeling to evaluate how climate and landscape characteristics interact to affect concentrations of total nitrogen, nitrate, and dissolved organic carbon across this diverse network of watersheds. Results indicate that at the continental scale, climate exerts the strongest influence on solute concentrations regardless of landscape characteristics. Large-scale data sets spanning time and space present the opportunity to develop a more complete understanding of how climate, terrestrial processes, and watershed characteristics interact to control emergent watershed biogeochemical properties including surface water chemistry.