Climate warming at northern latitudes is degrading permafrost and affecting precipitation patterns, thereby altering groundwater-surface water interaction. Northern communities and ecosystems that rely on predictable seasonal hydrologic patterns are directly affected by apparent increasing variability. Ni’iinlii Njik (Fishing Branch River) is a spring-fed river in northern Yukon underlain by continuous permafrost and karstic limestone that experiences seasonal dewatering cycles with irregular timing and extent. An extreme dewatering event in 2022 raised concerns among the Vuntut Gwitchin First Nation (VGFN) that the changing dewatering extent is contributing to an already declining chum salmon population. Annual dewatering is not unusual for rivers underlain by permafrost, but the increase in dewatering time and spatial extent at Ni’iinlii Njik contradicts the widely documented trend of higher baseflows in response to climate change. To understand dewatering patterns and trajectory, recent (2023-2025) water chemistry data from tributary springs, groundwater, and the main stem of the river will be compared with data from 2006-2008 and 2015-2017 to identify changes over nearly two decades. Statistical analysis of tracer data, namely δ18O, δ2H, Cl, and SO4, collected during the low-flow (April-May), peak-flow (June), and fall recession (October), will be used to assess whether the hydrologic variability is driven by precipitation, groundwater/permafrost dynamics, or a combination of both. Findings will improve our understanding of permafrost in karstic bedrock, permafrost-groundwater-surface water interactions, and hydrogeological effects on northern ecosystems. This research will also inform VGFN fishery managers who are working to mitigate climate change impacts on the chum salmon population.