<p>In 2020, numerous large wildfires, including the largest in Colorado history, burned watersheds that supply agricultural, industrial, and domestic drinking water to both sides of the Continental Divide. Increases in the size and frequency of severe wildfires such as these burning in headwater forests have implications for downstream water supply and aquatic ecosystems across western North America. Here, we evaluate stream water chemistry in 16 tributaries spanning a range of wildfire extent and severity during the first four years after the Cameron Peak Fire. As expected, stream water responses corresponded to the extent of severe wildfire, though temporal patterns differed among solutes reflecting distinct modes of transport from burned landscapes to streams. Wildfire ash and charred organic matter were alkaline and enriched in numerous water-soluble nutrients. Direct deposition of wildfire ash and smoke elevated stream K, PO₄-P and NH₄-N concentrations prior to significant post-fire precipitation. We observed repeated, short-lived spikes in stream PO₄-P, NH₄-N and turbidity following summer rainstorms, especially the first and second years after the fire. There was a large increase in dissolved organic carbon concentrations following the first intense post-fire rainstorms that more than doubled pre-fire levels and decreased gradually for nearly a year. In contrast, the stream nitrate response lagged until spring snowmelt runoff the second year after the fire, and the solute was less responsive to summer rainstorms. The chemical responses observed in headwater tributaries propagated downstream, where they may influence aquatic ecosystems and water supply to agricultural, residential and other uses. As a whole, these solute-specific patterns improve the understanding of water quality responses to projected increases in extreme wildfires in headwater forests and help prioritize areas that may benefit from post-fire restoration.</p> Graphical Abstract <p></p>