Identifying Wetland Consolidation Using Remote Sensing in the North Dakota Prairie Pothole Region

Abstract

Artificial drainage of wetlands in the Great Plains has been linked to increased runoff, erosion, and the consolidation of small, seasonal wetlands into larger, more permanent bodies of water. We analyzed hydrologic changes to over 1.2 million water bodies across the entire North Dakota portion of the Prairie Pothole Region using the ratio of aggregate water area and total perimetric length in a landscape-scale shape index calculated from existing Landsat derived data of water presence/absence. This ratio showed a clear change point toward more consolidation of wetlands around the period 1999 (±1 year) after an extended multiyear period of above-average rainfall. We used hydrologic simulations with forcing data from across the region to show that this shift is unlikely to be due solely to natural variation in precipitation and evapotranspiration. Using county-level regressions, we found that wetland consolidation as measured by the shape index was highly correlated with agricultural transitions out of wheat and into corn and soybeans over the period 1984–2014 (R2 > 0.4), though we do not find evidence of a strong correlation between reported drainage and wetland consolidation. These results highlight a potential hysteretic interaction involving interannual variations in hydrologic forcing and anthropogenic landscape alterations on wetland consolidation in the North Dakota prairie potholes.