Twenty‐Four Year Record Reveals Increasing Discharge in Tributaries to a Key Drinking Water Resource

ABSTRACT Climate change is altering precipitation patterns worldwide, yielding changes in streamflow and water availability. Increases in storm frequency and intensity, as well as prolonged droughts, may alter the timing and magnitude of flow and nutrient delivery to downstream systems, many of which serve as key drinking water resources. Thus, we must understand long‐term changes in streamflow to protect drinking water supplies. Here, we document changes in streamflow delivery to Beaver Lake Reservoir, the key drinking water source in rapidly urbanising Northwest Arkansas. We used publicly available data to analyse flow records in four key tributaries to Beaver Lake from 2000 to 2023. Total annual runoff increased significantly in three out of four tributaries to Beaver Lake ( R 2 = 0.15–0.23, p < 0.05) and was likely driven by increasing winter runoff ( R 2 = 0.15–0.20, p < 0.05). Flow duration analysis also indicated changes across flow categories were not consistent among the watersheds, which may present challenges in projecting future flow delivery to the reservoir. A case study from the West Fork of the White River revealed increases in flow did not yield increases in dissolved nutrient loads entering the reservoir from the watershed. Our results suggest that changing streamflow patterns may present a significant challenge in the predictability, timing, and quantity of water availability, and associated nutrient delivery, to Beaver Lake in Northwest Arkansas.