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Estimating wetland connectivity to streams in the Prairie Pothole Region: an isotopic and remote sensing approach
Citation:
Brooks, J. Renee, D. Mushet, M. Vanderhoof, S. Leibowitz, J. Christensen, B. Neff, D. Rosenberry, W. Rugh, AND L. Alexander. Estimating wetland connectivity to streams in the Prairie Pothole Region: an isotopic and remote sensing approach. WATER RESOURCES RESEARCH. American Geophysical Union, Washington, DC, 54(2):995-977, (2018).
Impact/Purpose:
Connectivity of water bodies within watersheds is of interest to the EPA because of its relevance to past Supreme Court decisions concerning the Clean Water Act (CWA). In this paper, we tested a new method for measuring hydraulic connectivity between prairie-pothole wetlands in North Dakota with downstream waters. Using water stable isotopes as indicators of wetland water and Landsat imagery, we estimated the dynamics of surface-water connectivity within the Pipestem Creek Watershed, a 1800 km2 watershed within the Prairie Pothole Region. We found that prairie-pothole wetlands were important sources of stream flow in Pipestem Creek throughout the summer, as well as during snowmelt. This work also demonstrated that at the lowest flows, the stream itself became disconnected from headwater stream reaches. This work is part of Task SSWR 3.01G: Quantifying Spatial and Temporal Gradients of Wetland Landscape Connectivity
Description:
Understanding hydrologic connectivity between wetlands and perennial streams is critical to understanding the reliance of stream flow on input from wetlands. We used the isotopic evaporation signal in water to examine wetland-stream hydrologic connectivity within the Pipestem Creek watershed, North Dakota, a watershed dominated by prairie-pothole wetlands. Pipestem Creek exhibited an evaporated-water signal that had approximately half the isotopic-enrichment signal found in most evaporatively enriched prairie-pothole wetlands. Groundwater measured at the water table next to Pipestem Creek had isotopic values that indicated recharge from winter precipitation and had no significant evaporative enrichment. Using isotopic theory and discharge data, we estimated the area of surface water necessary to generate the evaporation signal found within Pipestem Creek over two years. The range of evaporating area estimates was highly dynamic, spanning from 35 to 2380 ha of surface water contributing to streamflow over time, and varied primarily with the amount of discharge. The median area estimate (417 ha) was well above the surface-water area of the Pipestem Creek network (221 ha), and only one estimate was below. This indicated that prairie-pothole wetlands were important sources of stream flow in Pipestem Creek throughout the summer, as well as during snowmelt. This also demonstrated that at the lowest flows, the stream itself became disconnected from headwater stream reaches. We propose that this dynamic connectivity between prairie-pothole wetlands and Pipestem Creek occurred primarily when evaporatively enriched water stored in wetlands spilled into the stream during precipitation events.
