On the Development of a Regional Approach to Studying the Dynamics of Complex Lake-Watershed Systems of the Northern Great Plains

The extensive Prairie Pothole Region of North America contains millions of surface water bodies in the form of lakes, wetlands, and ponds. As a whole, they provide irreplaceable services to sustain wildlife, ecosystems, water resources, agriculture, and the economy. Because most of them are hydrologically “closed”, these water bodies are extremely sensitive to climate variability and are highly dynamic in terms of their numbers, water levels, areas, and storage.  In this paper, a new approach (i.e., space-for-time substitution) is applied to address the behaviors of these complex hydrologic systems in response to climatic variability. Space-for-time substitution has been long recognized in ecology and geomorphology as an essential, if not unique, approach to understanding long-term system dynamics. While the approach has been accepted qualitatively, validation has been a challenge. Here I present evidence from a suite of surface-water complexes along a climate gradient in the Prairie Pothole Region to both validate and apply space-for-time substitution. A comparison of the spatial and temporal trends of water-body population dynamics revealed a common pathway of response to climate variability in space and time. The validation of space-for-time substitution for these hydrologic systems not only answered an important science question in its own right, but improved understanding of climate-forcing and hydrologic-response mechanisms for pothole water bodies. This study also has important regional-scale implications including, for the first time, a complete picture of the heterogeneous spatial and temporal water-body distribution across the entire Prairie Pothole Region and an understanding of how the patterns of abundances of lakes and wetlands change as a function of climate variability.