Phosphorus Inputs to the Winnebago Pool Lakes

Prepared in cooperation with the U.S. Environmental Protection Agency Water-Quality Response to Changes in Phosphorus Loading of the Winnebago Pool Lakes, Wisconsin, with Special Emphasis on the Effects of Internal Loading in a Chain of Shallow Lakes Menasha ^ Lake Poygan Neenah ! ! 2 Lake Winneconne ! ^ ! 3 1 ^ 2 ! 1 3 ! Lake Butte des Morts ! ! 7 ! ! 1 2 ^3 ! ! ! nm Oshkosh X Lake EXPLANATION Winnebago 3 Bathymetric contour—Depth in meters ^ X Water level station ^ Lake sampling site nm Buoy # Gaging and sampling station ! Sediment core site #* River sampling site 6 ! ! Scientific Investigations Report 2018–5099 5 ^ 4 1 3 U.S. Department of the Interior 2 Fond du Lac U.S. Geological Survey Cover figure. Winnebago Pool Lakes, Wisconsin, and their watersheds, with sampling locations identified. Water-Quality Response to Changes in Phosphorus Loading of the Winnebago Pool Lakes, Wisconsin, with Special Emphasis on the Effects of Internal Loading in a Chain of Shallow Lakes By Dale M. Robertson, Benjamin J. Siebers, Matthew W. Diebel, and Andrew J. Somor Prepared in cooperation with the U.S. Environmental Protection Agency Scientific Investigations Report 2018–5099 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior RYAN K. ZINKE, Secretary U.S. Geological Survey James F. Reilly II, Director U.S. Geological Survey, Reston, Virginia: 2018 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Robertson, D.M., Siebers, B.J., Diebel, M.W., and Somor, A.J., 2018, Water-quality response to changes in phosphorus loading of the Winnebago Pool Lakes, Wisconsin, with special emphasis on the effects of internal loading in a chain of shallow lakes: U.S. Geological Survey Scientific Investigations Report 2018–5099, 58 p., https://doi. org/10.3133/sir20185099. ISSN 2328-0328 (online) iii Acknowledgments We would like to acknowledge Keith Marquardt and Kevin Kirsch of the Wisconsin Department of Natural Resources (WDNR), and Jean Chruscicki, Dave Werbach, and Alie Muneer of the U.S. Environmental Protection Agency (EPA) for their insight on stakeholder needs throughout the study. We thank Keith Marquardt and Mark Sesing (retired) of the WDNR for help with obtaining water-quality, septic, and point-source data used in this study and their helpful comments on the design of the study. We also thank Jean Chruscicki of the EPA and Emma Lorenzen of the WDNR for providing comments on earlier drafts of this report. We would like to acknowledge Paul Reneau, Peter Hughes (retired), Dave Owens, Troy Rutter, and Dan Olson (retired) of the U.S. Geological Survey (USGS) for help installing and operating the buoy on Lake Winnebago and for assistance collecting and processing river data. We thank Jim Kennedy of the USGS for assistance with creating maps for this report. We thank Herb Garn (retired) and Mary Anne Evans of the USGS for providing helpful comments on earlier drafts of this report. Funding for this study was provided by the U.S. Environmental Protection Agency as part of Great Lakes Restoration Initiative. v Contents Acknowledgments ........................................................................................................................................iii Abstract ...........................................................................................................................................................1 Introduction.....................................................................................................................................................1 Purpose and Scope ..............................................................................................................................4 Methods...........................................................................................................................................................4 Study Area..............................................................................................................................................4 Data Collection ......................................................................................................................................4 Lake Water Quality ......................................................................................................................4 Lake Morphometry.......................................................................................................................6 Lake Stage.....................................................................................................................................6 River and Tributary Monitoring and Load Computation .........................................................6 Sediment P Release ....................................................................................................................8 Meteorological Data ...................................................................................................................9 Numerical Watershed and Lake Models ..........................................................................................9 Watershed Model—SWAT .........................................................................................................9 Lake Models..................................................................................................................................9 Mass-Balance Model ........................................................................................................9 BATHTUB Model ...............................................................................................................10 Jensen Model ....................................................................................................................10 Lake Water Quality ......................................................................................................................................11 Hydrology and Water Budget ....................................................................................................................17 Changes in Water Level and Lake Volume .....................................................................................17 Surface-Water Inflow and Outflow ..................................................................................................18 Groundwater ........................................................................................................................................18 Precipitation.........................................................................................................................................18 Evaporation ..........................................................................................................................................18 Water Budget Summary ....................................................................................................................23 Phosphorus Inputs to the Winnebago Pool Lakes .................................................................................23 Nonpoint Surface-Water Inputs .......................................................................................................23 Precipitation.........................................................................................................................................27 Groundwater ........................................................................................................................................27 Septic Systems ....................................................................................................................................27 Point Sources ......................................................................................................................................27 Upstream Pool Lakes..........................................................................................................................30 Surface-Water Outflow ......................................................................................................................30 Release of Phosphorus from Lake Sediments ...............................................................................30 Accuracy of the Phosphorus Budget and Total Sediment P Release ........................................32 Summary of the Phosphorus Budgets for the Winnebago Pool Lakes ......................................32 Simulated Changes in Water Quality in Response to Changes in Phosphorus Loading ..................34 Water-Quality Modeling with BATHTUB .........................................................................................34 Data Requirements ....................................................................................................................36 Algorithms and Calibration .......................................................................................................36 Response in Water Quality

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