Prairie Wolf Slough: A Case Study Illustrating the Need for Incorporating Land Use History and Soil Quality Assessment in Wetland Restoration Planning, Design and Monitoring.

This presentation is a cautionary tale of what can happen when past land use history and assessment of soil quality are not incorporated into wetland restoration protocols. In suburban Chicago, restored wetlands are used to improve water quality in streams degraded by agriculture and urban development. Since 1998 we have monitored water quality at Prairie Wolf Slough (PWS), a restored wetland located on abandoned farm fields adjacent to the Chicago River in north suburban Chicago. PWS receives surface runoff from residential and commercial land uses, and it discharges into the Chicago River. The objectives of this study are to assess spatial and temporal variations in water flow, selected nutrient and solids loadings, and compute a mass balance and retention efficiency. Water samples continue to be collected at inlet and outlet discharge points. Soil samples and a suite of plant species were collected in 2012 from the wetland and adjacent upland plant communities and analyzed for phosphorus. Loadings of nitrogen and solids are effectively reduced at the outlet point; however, long-term average loadings of TP and SRP increased 279%, indicating that PWS is a point source of phosphorus into the Chicago River. Soil testing and analysis of phosphorus release from decaying vegetation suggest that phosphorus export is due to exposure of legacy fertilizer P-laden sediment to anoxic conditions during flood events and microbial decay of biomass. The phosphorus data clearly demonstrate the need for researching land use history and including soil quality assessment into wetland restoration planning, design and monitoring protocols.