Quantifying hydrologic connectivity of wetlands to surface water systems

Abstract. Hydrologic connectivity among wetlands is poorly characterized and understood. Our inability to quantify this connectivity compromises our understanding of the potential impacts of wetland loss on watershed structure, function and water supplies. We develop a computationally efficient, physically based subsurface–surface hydrologic model to characterize both the subsurface and surface hydrologic connectivity of geographically isolated wetlands and explore the time and length variations in these connections to a river within the Prairie Pothole Region of North America. Despite a high density of geographically isolated wetlands (i.e., wetlands without surface inlets or outlets), modeled connections show that these wetlands are not hydrologically isolated. Subsurface connectivity differs significantly from surface connectivity in terms of timing and length of connections. Slow subsurface connections between wetlands and the downstream river originate from wetlands throughout the watershed, whereas fast surface connections were limited to large events and originate from wetlands located near the river. This modeling approach provides first ever insight on the nature of geographically isolated wetland subsurface and surface hydrologic connections to rivers, and provides valuable information to support watershed-scale decision making for water resource management.