1. The Confounding Effect of River Discharge on Estuarine Response to Nutrient Loading Borsuk, M. E., C. A. Stow, and K. H. Reckhow. 2004. Confounding effect of flow on estuarine response to nitrogen loading. Journal of Environmental Engineering, 130: 605-614. Craig A. Stow NOAA Great Lakes Environmental Research Laboratory Ann Arbor, MI Additional Insights and Inputs provided by Conrad Lamon and Song Qian

2. The Neuse River Basin Courtesy USGS

4. Vollenweider Cross-Sectional Lake Nutrient Loading Model Brazenly stolen from: Vollenweider, R.A. 1976. Advances in defining critical loading levels for phosphorus in lake eutrophication. Mem. Ist. Ital. Idrobiol., 33:53-83. Single Lake Relationship: Positive Negative  Nonlinear

5. River Flow Nutrient Loading Nutrient Concentration Eutrophication Estimated Nutrient Loading Estimated Concentration= f(Flow) Residence Time Turbidity Salinity Temperature

6. River discharge highly variable – even on relatively long time-scales Drives Nutrient Load Variability at this scale

7. Concentration:Flow relationships idiosyncratic: positive, negative, or non-monotonic In the Neuse the relationship was negative Log flow Log concentration Data Provided by: NC DENR DWQ – nutrient concentrations USGS – daily flow  High load = low concentrations

8. New Bern Bern 10 miles 10 kilometers 10 20 30 40 50 0 60 70 80 90 100 110 120 130 140 150 160 170 180 N N Water Quality Station Water Quality Station Hydrographic Station Hydrographic Station Water Quality Station Water Quality Station Hydrographic Station Hydrographic Station River Upper Middle Bend Lower Upper Middle Bend Model Sections

9. Chlorophyll a Model (Bayesian multilevel piecewise lognormal model)

10. Ft. Barnwell Swift Creek New Bern Broad Creek Oriental Pamlico Estuarine N Concentrations vs. Annual N Load

11. Ft. Barnwell Swift Creek New Bern Broad Creek Oriental Pamlico Estuarine P Concentrations vs. Annual P Load

12. Summary Nonlinear chlorophyll, flow (~ load) relationship on short time-scales Relationship differs systematically along spatial gradient Maximum differs systematically along spatial gradient No relationship between nutrient load, concentration on medium time-scales This may differ among systems

13. Nutrient Loading Eutrophication Hypoxia Nutrient Loading TMDLs Eutrophication Hypoxia

14. Nutrient load targets appropriate on longer (multi-year) time scales Short-term (yearly or less) misleading  Assuming stationary flow (long-term)

15. Mississippi River Flow – Seasonal Trend Decomposition Using Loess

16. April 2006 - U.S. Court of Appeals District of Columbia Circuit ruled that EPA- approved plan to limit pollution into Anacostia River contrary to Clean Water Act requirements to set "total maximum daily loads" of pollutants. January 2007 -- United States Supreme Court let stand lower court ruling requiring limits on pollution allowed in Anacostia River each day. Anacostia River in Washington, DC Photo by City of Washington DC

17. River Flow Nutrient Loading Nutrient Concentration Eutrophication Upper Trophic Level Effects Hypoxia ?

18. The End

19. River Flow Nutrient Loading Hypoxia Estimated Nutrient Loading