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Streamflow derived from montane environments is important for downstream communities but is vulnerable due to decreasing snowpack from climate change. Earlier peak flows induced by warming conditions will cause lower summer flows leading to an increased reliance on groundwater. Although snowpacks are the dominant source of streamflow in southwestern montane environments, monsoon rains can also provide significant precipitation inputs to these regions during the summer and fall months and may provide a buffer to streamflow in low snowpack years. Groundwater – surface water relationships are further complicated given the complex controls geology exerts on spatial and temporal patterns of groundwater discharge. Local scale features can play an important role in the locations and volume of groundwater discharge and degree of groundwater-surface water interactions. Using high spatial and temporal resolution radon and stream chemistry sampling, we attempt to unravel the control of bedrock fractures on groundwater contributions and groundwater-surface water interactions in the Coal Creek watershed, a montane headwater stream impacted by summer monsoons. Stream water samples were collected between June and September 2021 and analyzed for anions, cations, water isotopies, and radon. In general, radon concentrations increase with movement downstream and during dry periods indicating higher groundwater contributions during these periods. Geogenic constituent concentrations increase throughout the summer, however despite these increasing concentrations, there is a decrease in radon concentrations throughout the summer. This perhaps indicates of a snowmelt-driven pulse of groundwater accompanying elevated stream discharge at the beginning of the summer. Overall, it appears that radon tracks how precipitation influences groundwater-surface water interactions in fracture zones.