Operational Environmental Prediction: Nearshore Water Quality in the Great Lakes

1. Operational Environmental Prediction: Nearshore Water Quality in the Great Lakes David J. Schwab NOAA Great Lakes Environmental Research Laboratory Ann Arbor, MI

2. Factors Contributing to Nearshore Water Quality in the Great Lakes Climate – Meteorology – Hydrology – Hydrodynamics – Biology/Chemistry

3. Forecasting Beach Closings or HABs Meteorology Meteorology Change in Land-use Change in Land-use Change in Land-use Hydrology/Water Flow Bacterial Fate Hydrology/Water Flow Bacterial Fate Beach Closings Circulation and Bacterial Fate Circulation and Bacterial Fate

4. Outline Lake Michigan tributary modeling using nested-grid hydrodynamic models - application to beach water quality forecasting Lake Erie coupled physical/biological model - application to HAB and hypoxia forecasting

5. Beach Closures • Major health risk of microbial contamination by bacteria, viruses and protozoa in recreational waters • E.Coli requires a 24 hour incubation period • People may unintentionally swim in contaminated water

7. Lake Michigan Beach Quality Forecasting Lakewide grid (POM model) Coupled models nested grids + Burns Ditch nested model grid

8. Princeton Ocean Model (Blumberg and Mellor, 1987) - Fully three-dimensional nonlinear Navier-Stokes equations - Flux form of equations - Boussinesq and hydrostatic approximations - Free upper surface with barotropic (external) mode - Baroclinic (internal) mode - Turbulence model for vertical mixing - Terrain following vertical coordinate (<sigma>-coordinate) - Generalized orthogonal horizontal coordinates - Smagorinsky horizontal diffusion - Leapfrog (centered in space and time) time step - Implicit scheme for vertical mixing - Arakawa-C staggered grid - Fortran code optimized for vectorization Application to the Great Lakes - No open boundary - No tides - Uniform salinity - Seasonal thermal structure - Uniform rectangular grid - XDR used for input and output • Nested grid considerations: • 3d boundary condition for u, v, and T interpolated from coarse grid at each boundary point • Vertically integrated velocity is specified for external mode • Internal mode velocity and temperature are specified from 3-d boundary condition for inflow, use radiation condition for outflow • Water level is adjusted to maintain zero mean in nested grid subdomain

9. Nested grid hydrodynamic models in Lake Michigan

10. Burns Ditch 100m computational grid 24 km 6 km

11. Web site: www.glerl.noaa.gov/res/glcfs/bd

16. Great Lakes Coastal Forecasting System - Operational Nowcast 20 day sample using vertically averaged currents

17. Lake Erie Coupled Physical/Biological model

18. The Problem: - Excessive nutrient loading in the 1960’s led to massive algal blooms, oxygen depletion, and diminished water quality in Lake Erie. - 1972 Water Quality Agreement between the US and Canada limited P loads from municipal, industrial, and agricultural sources. - With controls, P levels decreased to acceptable levels and water quality improved. - In recent years, P levels in Lake Erie appear to be increasing, despite controls.

19. The Problem: - Excessive nutrient loading in the 1960’s led to massive algal blooms, oxygen depletion, and diminished water quality in Lake Erie. - 1972 Water Quality Agreement between the US and Canada limited P loads from municipal, industrial, and agricultural sources. - With controls, P levels decreased to acceptable levels and water quality improved. - In recent years, P levels in Lake Erie appear to be increasing, despite controls. Our Approach: - Incorporate phosphorus transport and fate dynamics into high resolution (hourly time scale, 2 km horizontal resolution) hydrodynamic model of Lake Erie as a first step toward spatially explicit model of entire lower food web

20. Lake Erie Physical Characteristics: Surface Area: 25800 km2 Throughflow ~ 6000 m3s-1 Volume: 480 km3 Retention time: 2.5 yrs Mean Depth: 18.6 m

21. Ecosystem Forecasting of Lake Erie Hypoxia • What are the Causes, Consequences, and Potential Remedies of Lake Erie Hypoxia? • Linked set of models to forecast: • changes in nutrient loads to Lake Erie • responses of central basin hypoxia to multiple stressors • P loads, hydrometeorology, dreissenids • potential ecological responses to changes in hypoxia • Approach • Models with range of complexity • Consider both anthropogenic and natural stressors • Use available data – IFYLE, LETS, etc. • Will assess uncertainties in both drivers and models • Apply models within an Integrated Assessment framework to inform decision making for policy and management

22. Hypoxia Forecasting Modeling Approach • Model ranging in complexity • Correlation-based models • 1D hydrodynamics with simple mechanistic WQ model • Vertical profiles extracted from full hydrodynamic model • TP, Carbon, Solids • 3D hydrodynamics with simple mechanistic WQ model • Physics from full hydrodynamic model • 3D hydrodynamics with complex mechanistic WQ model • WQ framework similar to Chesapeake Bay ICM model • Multi-class phyto- and zooplankton, organic and inorganic nutrients, sediment digenesis, etc • Addition of zebra mussels and other improvements

23. Chapra, S.C. 1980. J. Great Lakes Res. 6(2):101-112.

24. Effect of Phosphorus Controls on Lake Erie Central Basin Springtime P Concentration (Ryan et al., 1999)

25. Lake Erie 1994 physical/biological model • Hydrodynamics • - Great Lakes version of POM • 20 vertical levels, 2 km horizontal grid (~6500 cells) • Hourly meteorology (1994, JD 1-365) • Realistic tributary flows • Accounts for ice cover • Mass balance for P • POM hydrodynamics (2d for now) • Realistic P loading • Constant settling velocity (for now)

26. Computer animation of model results: • Starts in January, 1994 • Uses 2d currents from hydrodynamic model • Time dependent P loads • Combination Lax-Wendroff and upwind advection scheme • No horizontal diffusion • Initial condition: C = 10 ug/L • Settling velocity = 6.8E-7 m/s (21 m/yr)

27. Questions?