On the Great Plains of North America, water resources are being threatened by climatic shifts. However, a lack of hillslope-scale climate-runoff observations is limiting our ability to understand these impacts. Here, we present a 52-year (1962-2013) dataset (precipitation, temperature, snow cover, soil water content, and runoff) from three 5 ha hillslopes on the seasonally-frozen northern Great Plains. In this region, snowmelt-runoff drives c. 80% of annual runoff and is potentially vulnerable to warming temperatures and changes in precipitation amount and phase. We assessed trends in these climatological and hydrological variables using time series analysis. We found that spring snowmelt-runoff has decreased (on average by 59%) in response to a reduction in winter snowfall (by 18%), but that rainfall-runoff has shown no significant response to a 51% increase in rainfall or shifts to more multi-day rain events. In summer, unfrozen, deep, high-infiltrability soils act as a 'shock absorber' to rainfall, buffering the long-term runoff response to rainfall. Meanwhile, during winter and spring freshet, frozen ground limits soil infiltrability and results in runoff responses that more closely mirror the snowfall and snowmelt trends. These findings are counter to climate-runoff relationships observed at the catchment scale on the northern Great Plains where land drainage alterations dominate. At the hillslope scale, decreasing snowfall, snowmelt-runoff, and spring soil water content is causing agricultural productivity to be increasingly dependent on growing season precipitation, and will likely accentuate the impact of droughts.
We thank the many Agriculture and Agri-Food Canada researchers, technicians, and students who have collected these 52 years of data. We especially want to extend our thanks to Don Reimer and Marty Peru, who dedicatedly minded the hillslopes from 1971 to 1994, and from 1995 to 2011, respectively. This study was supported by funding from an NSERC Discovery Grant and Accelerator grant to JJM and from the Global Institute for Water Security. We thank Rosa Brannen, Willemijn Appels, Stacey Dumanski, Natalie Orlowski, Chris Gabrielli, Dyan Pratt, and two anonymous reviewers for comments on earlier drafts of this paper.
- Great Plains
- Climate change