Solute export dynamics from watersheds provide critical insights into the hydrological and ecological conditions of terrestrial and aquatic ecosystems. However, how information signals from nested subcatchments integrate across stream networks to monitoring locations remains an open question. To investigate how solute exports evolve over stream networks, we used high-frequency sensor data collected at 15-minute intervals over one season to examine concentration-discharge (C-Q) relationships for nitrate (NO₃⁻) and dissolved organic carbon (DOC) at two sites at the top and bottom of a headwater stream network. The stream network is in the upper Santa Fe watershed in the American Southwest, which has steep elevational gradients in water availability and delivers critical water supplies to downstream populations.
Our results of C-Q patterns in 30-day rolling windows reveal significantly less discharge variability at the headwater site compared to the outlet. Despite this, DOC and NO₃⁻ dynamics showed similar temporal patterns at both sites, suggesting mechanisms that buffer solute export variability in the upper watershed. DOC consistently exhibited flushing behavior across both sites (positive slopes), indicating a stable carbon source likely regulated by vegetation or shallow subsurface flows. Conversely, NO₃⁻ dynamics displayed pronounced seasonal and spatial differences. At the headwater site, flushing occurred during monsoon-driven connectivity to nitrogen sources, while dilution dominated in the fall and winter possibly due to biological uptake. At the outlet, NO₃⁻ showed more frequent dilution patterns with occasional flushing during snowmelt and post-monsoon events, pointing to heterogeneity in upstream processes. These findings highlight the complex interplay between hydrology, biological demand, and spatial heterogeneity in shaping nutrient export, providing valuable perspectives for understanding solute transport in headwater systems.