Prepared in cooperation with the U.S. Fish and Wildlife Service A Metabolism-Based Whole Lake Eutrophication Model to Estimate the Magnitude and Time Scales of the Effects of Restoration in Upper Klamath Lake, South-Central Oregon Scientific Investigations Report 2018–5042 U.S. Department of the Interior U.S. Geological Survey Cover: Photograph showing Aphanizomenon flos-aquae cluster in Upper Klamath Lake, south-central Oregon. Photograph by Susan Wherry, U.S. Geological Survey, July 15, 2015. A Metabolism-Based Whole Lake Eutrophication Model to Estimate the Magnitude and Time Scales of the Effects of Restoration in Upper Klamath Lake, South-Central Oregon By Susan A. Wherry and Tamara M. Wood Prepared in cooperation with the U.S. Fish and Wildlife Service Scientific Investigations Report 2018–5042 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior RYAN K. ZINKE, Secretary U.S. Geological Survey William H. Werkheiser, Deputy Director exercising the authority of the 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. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service. 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: Wherry, S.A., and Wood, T.M., 2018, A metabolism-based whole lake eutrophication model to estimate the magnitude and time scales of the effects of restoration in Upper Klamath Lake, south-central Oregon: U.S. Geological Survey Scientific Investigations Report 2018–5042, 43 p., https:/doi.org/10.3133/sir20185042. ISSN 2328-0328 (online) iii Contents Abstract ...........................................................................................................................................................1 Significant Findings .......................................................................................................................................1 Introduction.....................................................................................................................................................2 Purpose and Scope ..............................................................................................................................4 Datasets...........................................................................................................................................................5 Klamath Tribes Water-Quality Samples ............................................................................................5 Load Calculations..................................................................................................................................5 U.S. Geological Survey Continuous Monitors ..................................................................................5 U.S. Geological Survey Water-Quality Samples ..............................................................................7 AgriMet Solar Radiation ......................................................................................................................7 Whole Lake Eutrophication Model for Simulating Historical Conditions .............................................7 Biomass ..................................................................................................................................................7 Net Primary Production ..............................................................................................................7 Whole-Lake Mass Calculation .......................................................................................10 Gas Transfer and Sediment Oxygen Demand ..............................................................12 Whole-Lake Metabolism Calculation ............................................................................12 Quantification of Uncertainty in Net Primary Production Calculations ..........13 Calculation of the Ratio of Carbon to Chlorophyll a in Cyanobacteria Cells ...................................................................................15 Phosphorus .........................................................................................................................................18 Calibration of Algal Settling Velocity ......................................................................................18 Determination of Algal Phosphorus ........................................................................................19 Calibration of Internal Recycling .............................................................................................20 Calibration of the Non-Algal Phosphorus Removal Rate ....................................................22 pH...........................................................................................................................................................22 Model Performance............................................................................................................................22 Multivariate Regression Model of Net Primary Production .................................................................25 Predictor Variables .............................................................................................................................25 Water Temperature ...................................................................................................................25 Stratification ...............................................................................................................................25 Solar Radiation ...........................................................................................................................27 Wind Speed.................................................................................................................................27 Total Phosphorus and Chlorophyll a Concentration .............................................................27 Filtering with Wavelet Analysis ........................................................................................................27 Net Primary Production Regression Model ...................................................................................27 Whole Lake Eutrophication Model for Simulating Future Conditions .................................................33 Model Performance............................................................................................................................33 Long-Term Simulations ......................................................................................................................33 Implications of Model Results for Restoration ......................................................................................38 Summary........................................................................................................................................................41 References Cited..........................................................................................................................................42 iv Figures 1. Map showing location of meteorological stations and continuous and discrete water-quality monitoring sites, Upper Klamath Lake, south-central Oregon .....................3 2. Flowchart showing whole lake eutrophication model dependencies using calculated net primary production ............................................................................................8 3. Scatterplots showing average dissolved oxygen in the upper 2 meters of the water column, as a function of the corresponding hourly measurement collected at 1 meter in depth, at U.S. Geological Survey core sites of Mid-North (MDN), Upper Klamath Lake at Williamson River outlet (WMR), Mid-Trench (MDT), and Rattlesnake Point (RPT), Upper Klamath Lake, south-central Oregon ..............................11 4. Graph showing cumulative fraction of total lake surface area as a function of depth at full pool and the full-pool depths for the four U.S. Geological Survey core water-quality monitoring sites, Upper Klamath Lake, south-central Oregon ...................11 5. Graph showing carbon-to-chlorophyll a ratio of water samples collected in Upper Klamath Lake, south-central Oregon, June–September 2011 .............................................17 6. Graph showing carbon-to-chlorophyll a ratio of water samples collected in Upper Klamath Lake, south-central Oregon, August 18–19, 2011 ...................................................17 7. Boxplot showing relative percentage of difference in carbon-to-chlorophyll a ratio of water samples collected in Upper Klamath Lake, south-central Oregon, June–September 2011 ...............................................................................................................17 8. Graphs showing results of recalibrating the algal settling velocity parameter by using net primary production ....................................................................................................18