Lake basins drive variation in catchment‐scale runoff response over a decade of increasing rainfall in Arctic Alaska

Abstract

AbstractLakes basins cover wide extents of many Arctic Coastal Plain (ACP) landscapes and thus are integral components of hydrological processes. Observed variation in runoff responses between two adjacent catchments being monitored pre‐ and post‐development in the National Petroleum Reserve in Alaska (NPR‐A) suggested the need to better understand how lake basins, both current lakes and drained lake basins (DLBs), modify flow regimes. A progressive increase in summer rainfall over this monitoring period, 2009–2019, also provided an opportunity to assess how watershed characteristics interacted with hydrologic intensification. Stream gauging records from eight other nearby catchments ranging from 16 to 270 km2 with varying extents of lakes (14%–47%) and DLBs (5%–57%) expanded our analysis of ACP hydrology. Wider DLB extent corresponded to higher and more rapid snowmelt peak flows and this relationship also became evident during rainstorms in summers with high antecedent surface storage. Mean annual runoff and summer low‐flows were best explained by extent of connected lakes. Over this period of increasing summer rainfall, all hydrograph responses became more closely related to the full extent of lake basins suggesting expanding connectivity. Our final year of complete hydrologic records in 2019 was punctuated by a 30‐mm late‐summer rainfall event, which generated flow peaks nearly exceeding snowmelt runoff at several gauges, specifically ones with high extent of DLBs. This rain‐event response underscored the increasing need to include both lakes and DLBs in models of ACP watershed hydrology. An improved understanding of catchment‐scale controls on variable hydrologic responses will be increasingly essential for mitigating hazards to new and existing development, predicting floods, drought, and water supply, and protecting aquatic ecosystem functioning and habitat as the Arctic hydrologic cycle intensifies and development expands.