Patterns and drivers for wetland connections in the Prairie Pothole Region, United States

Abstract

Ecosystem function in rivers, lakes and coastal waters depends on the functioning of upstream aquatic ecosystems, necessitating an improved understanding of watershed-scale interactions including variable surface-water flows between wetlands and streams. As surface water in the Prairie Pothole Region expands in wet years, surface-water connections occur between many depressional wetlands and streams. Minimal research has explored the spatial patterns and drivers for the abundance of these connections, despite their potential to inform resource management and regulatory programs including the U.S. Clean Water Act. In this study, wetlands were identified that did not intersect the stream network, but were shown with Landsat images to become merged with the stream network as surface water expanded. Wetlands were found to spill into or consolidate with other wetlands within both small (2-10 wetlands) and large ([100 wetlands) wetland clusters, eventually intersecting a stream channel, most often via a riparian wetland. These surface-water connections occurred over a wide range of wetland distances from streams (averaging 90-1400 m in different ecoregions). Differences in the spatial abundance of wetlands that show a variable surface-water connection to a stream were best explained by smaller wetland-to-wetland distances, greater wetland abundance, and maximum surface-water extent. This analysis demonstrated that wetland arrangement and surface water expansion are important mechanisms for depressional wetlands to connect to streams and provides a first step to understanding the frequency and abundance of these surface-water connections across the Prairie Pothole Region.

Connectivity of Streams and Wetlands to Downstream Waters: An Integrated Systems Framework

“…For example, Vanderhoof, Christensen, et al. () found that the average distance over which wetlands showed a surface‐water connection to streams varied substantially between ecoregions across the prairie pothole region. In areas dominated by flat, open basins and lakes, small changes in surface‐water levels can consolidate wetlands that were previously disconnected by distances >1 km (Vanderhoof and Alexander ).…”

Modelling surface‐water depression storage in a Prairie Pothole Region

“…The PRMS depression storage essentially behaves as fill and merge, with fill and spill limited to periods of excessive storage (based on the dprst_dept_avg parameter [average depth of the surface‐water depression storage at maximum storage capacity for each HRU; Figure c]) making it more of a “merged, fill, and spill” conceptualization. Fill and merge can contribute to streamflow, expanding and merging with a stream‐intersect wetland (Vanderhoof, Christensen, & Alexander, ). As noted by Leibowitz et al (), fill and spill leads to more streamflow out of the basin, whereas fill and merge results in more internal basin storage.…”

Modeling Connectivity of Non‐floodplain Wetlands: Insights, Approaches, and Recommendations

“…; Vanderhoof et al. ) have all significantly increased our ability to characterize hydrologic fluxes between NFWs and other watershed components. These empirical characterizations are important for developing a fundamental understanding of the system in question (see Burt and McDonnell ) but are often limited in spatial domain and measurement period.…”

“…), remotely sensed imagery to determine spatial and temporal patterns of wetland inundation (Vanderhoof and Alexander ; Vanderhoof et al. ), and water isotope analysis to examine potential contribution of wetlands to streamflow (Brooks et al. ).…”