Wildfires impact watersheds in varied ways, with complex relationships between burn and watershed characteristics influencing downstream aquatic biogeochemistry. In particular, wildfire alterations to the terrestrial landscape influence water delivery to stream networks which can have hard-to-predict impacts on organic matter (OM) chemistry and related biogeochemical processes in streams. Here we present an ongoing case study exploring wildfire impacts on hydrologic connectivity across a small watershed that was entirely burned, and the resulting impacts on aquatic biogeochemistry. In November 2024, four months after fire ignition, we established five sites across the Oak Creek watershed in the Yakima River Basin in Washington, USA. Each site is equipped with YSI EXO2 sondes to measure temporally resolved proxies for groundwater inputs (specific conductivity) and fluorescent dissolved OM (fDOM) along with basic water quality (including dissolved oxygen) and depth. We also collect end-member samples from precipitation, the hyporheic zone, soil leachates, and deep groundwater across the watershed to assess end-member contributions to the streams. Previous work has suggested that groundwater contributions may mediate the relationship between OM chemistry and burn severity in streams draining burned watersheds. Therefore, we explored the relationship between stream OM chemistry and subsurface contributions to streams across the watershed. We found spatiotemporal differences in the contributions of groundwater across our sites, based on specific conductance and hydrologic tracer simulations. This corresponded to shifts in OM signatures over the study period and predicted hillslope contributions of OM to the river corridor. We find that spatial and temporal variability in wildfire impacts on OM quality in streams post-fire is dependent on sub-watershed variations in hydrologic connectivity.