Mechanisms of Cold Region Hydrologic Change to Recent Wetting in a Northern Glaciated Landscape

Abstract

AbstractThe Northern Great Plains (NGP) experienced a transition from a long drought cycle to a deluge cycle in the late 1900s. Embedded within this long‐term transition were shorter‐term decadal‐scale dry and wet periods. A recent NGP drought (1999–2004) was followed in 2005 by a wet period that continues to present day. However, how surface hydrology in a northern glaciated landscape responds to increased precipitation is poorly understood and a physically based modeling framework is needed to clarify the underlying processes. This study utilizes a physically based hydrologic model to investigate the impacts of increased precipitation on the water budget by examining its partition into intermediate processes from 2004–2017 in the Mauvais Coulee Basin (MCB). The MCB model evaluations against snow observations (2016–2017) and outlet streamflow observations (2004–2017) imply strong model performance. Simulated snow exhibits high spatiotemporal variation due to variability in precipitation, snow redistribution from stubble fields to wooded areas, and snow accumulation in small depressions. Our modeling results identify two major phases (before and after 2011) exhibiting different hydrologic responses. The period before 2011 is dominated by streamflow and evapotranspiration (ET), while extreme ET dominance is observed after 2011. This switch is due to climatic conditions involving changes in the vapor density difference and depressional and subsurface storage by intermediate processes. A clear contrast in the prewinter soil moisture‐streamflow relationship between before and after 2011 is reported. Our findings help illuminate the important influences of increased precipitation upon the intermediate processes in controlling streamflow in a northern glaciated prairie landscape.