Relationships between surface water area and hydrologic fluxes in a cold region terminal lake basin

Study region

Northern Great Plains (NGP), North Dakota, USA

Study focus

Recent climate shifts have caused a prolonged wet period in the NGP since 1993, significantly expanding surface water area and hydrological connectivity. However, the spatiotemporal links between the water connectivity and hydrologic fluxes remain poorly understood in terminal basins like the Devils Lake Basin (DLB), and accurately estimating open water evaporation (OWE) in this cold region is challenging due to winter ice cover. In this study, we developed a modified framework for estimating OWE in cold regions and investigated the spatiotemporal dynamics of water connectivity and hydrological fluxes.

New hydrologic Insights

The modified framework produced an average annual net evaporation of 785 mm (2000–2015), closely matched with the USGS estimation (825 mm). A clear hysteresis loop between OWE and both permanent and summer water areas reflected wetting (1996–2011) and drying (2013–2018) phases, highlighting a nonlinear response to shifting climate conditions. Strong nonlinear correlations were found between water connectivity and streamflow across the DLB (R² = 0.49–0.79). While Random Forest model captured this nonlinearity in training (NSE = 0.37–0.68), predictive performance declined during testing (NSE = 0.15–0.46), underscoring the region’s climatic and geomorphic complexity. Multiple Linear Regression revealed spatial heterogeneity in streamflow drivers: water connectivity in western subbasins, precipitation in the north-central, and temperature in the east. These findings highlight the need to consider nonlinearity and spatial variability in cold-region water modeling under climate change.