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Puget Sound Georgia Basin Model

Water-Quality and Biogeochemical Model Framework

The Salish Sea Model (SSM) water-quality computational framework was designed to simulate the influence of nutrients and carbon on biogeochemical oceanographic processes such as phytoplankton primary productivity and dissolved oxygen (DO) concentrations. PNNL and Washington State Department of Ecology in consultation with a Model Technical Advisory Committee of experts selected the CE-QUAL-ICM model, a state-of-the-art biogeochemical code developed by the U.S. Army Corps of Engineers (Cerco and Cole 1995) for coupling to the Finite Volume Coastal Ocean Model (FVCOM). It is capable of simulating 32 state variables, including multiple algae, carbon, multiple zooplankton, phosphorus, nitrogen, silica, and DO. Aquatic vegetation, benthic deposit feeders, and a predictive sub-model to calculate the interactive fluxes of DO and nutrients between the sediment and the water columns are also available. The use of the carbon cycle as the basis for eutrophication calculations, the ability to include sediment diagenesis, and the use of a finite volume approach were important considerations in selecting of the CE-QUAL-ICM model for the SSM domain. The rationale for selecting the FVCOM model for hydrodynamics and CE-QUAL-ICM kinetics for water quality for the SSM domain is described in the Model Selection Recommendations technical memorandum (Khangaonkar and Kim 2009) and the project quality assurance plan (Sackmann 2009). Kinetics simulated by the model are described in detail by Cerco and Cole (1995) and are schematically represented in the diagrams below.

Note that sediment diagenesis and pH modules were added subsequently (Pelletier et. al. 2017a, Pelltier et al. 2017b, Bianucci et al. 2018) and are also described at the Sediment Diagensis and pH pages. The biogeochemical model of the Salish Sea is described under Water Quality Validation and in Khangaonkar et al. (2018).

Model Carbon Cycle

Model Nitrogen Cycle

Model Phosphorous Cycle

Model DO Cycle

Source: Cerco, C.F., Noel, M.R., and Kim, S.C. (2004). Three-Dimensional Eutrophication Model of Lake Washington, Washington State. ERDC/EL TR-04-12, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi.

The SSM water-quality component currently set up to simulate the following 21 state variables:

  1. Algae Species 1 – diatom
  2. Algae Species 2 – dinoflagellates
  3. Dissolved organic carbon (DOC) – labile
  4. DOC – refractory
  5. Particulate organic carbon (POC) – labile
  6. POC – refractory
  7. Ammonium (NH4)
  8. Nitrate+Nitrite (NO3+NO2)
  9. Dissolved organic nitrogen (DON) – labile
  10. DON – refractory
  11. Particulate organic nitrogen (PON) – labile
  12. PON – refractory
  13. Phosphate (PO4)
  14. Dissolved organic phosphorus (DOP) – labile
  15. DOP – refractory
  16. Particulate organic phosphate (POP) – labile
  17. POP – refractory
  18. Particulate inorganic phosphate
  19. Dissolved oxygen.
  20. Dissolved Inorganic Carbon (DIC)
  21. Total Alkalinity

Salish Sea Model Overview

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