Mountainous catchments in the western U.S. are increasingly experiencing variable snowpack and precipitation patterns, yet the implications of this increasing hydroclimatic variability for solute fluxes from watersheds remain poorly understood. These dynamics are especially relevant in the Dog Valley watershed (62 km²), situated in the northeastern Sierra Nevada mountains, which encompasses an elevation gradient from alpine headwaters to semi-arid foothills. To investigate how solute fluxes across a stream network covary with the expansion and contraction of surface water across the network, we conducted synoptic sampling from July to November 2024 across eighteen sites categorized by nested sub-catchment sizes: Small Catchments (up to 1 km²; 5 sites), Medium Catchments (1–3 km²; 7 sites), and Large Catchments (greater than 3 km²; 6 sites). We also deployed high-frequency dissolved oxygen (DO) and temperature sensors at six locations chosen to capture a range of hydrologic conditions that may influence temporal variability in redox conditions and therefore nutrient transformations.
Preliminary results revealed a strong relationship between sub-catchment size and the extent to which a sub-catchment acts as a source or dilutor of solutes. Larger sub-catchments consistently diluted solutes, with mean leverage values ranging from -11 to -106, while smaller sub-catchments exhibit lower leverage magnitudes and are more likely to act as solute sources, with mean leverage values between 10.2 and -9.03.
Dissolved oxygen regimes exhibited significant variability, ranging from nearly anoxic to supersaturated conditions across sites. Small catchments showed substantial fluctuations, with DO ranges spanning from 0.5–4.3 mg/L to 8.3–15.9 mg/L. These variations, observed both within and across sub-catchments, underscore the critical influence of redox processes and hydrologic connectivity.
Overall these results highlight the complexity of solute transport processes in mountain-to-dryland catchments and provide insight into how shifting precipitation regimes and flow variability influence watershed solute dynamics.