Digital Signal Processing Reference
In-Depth Information
Figure (7-16): The 2D water quality modelling components of the shallow lake
The water quality and eutrophication models are coupled with the 2D hydrodynamic model developed
for the water body. The Delft3D-WAQ module is used for the water quality modeling component
coupled with the hydrodynamic module. Delft3D-WAQ is a 3-dimensional water quality modelling
framework within the D3D modeling package. It solves the advection diffusion- reaction equation on a
predefined computational grid for a wide range of model determinands. Delft3D-WAQ allows great
flexibility in the substances to be modeled, as well as in the processes to be considered. It is important
to note that Delft3D-WAQ is not a hydrodynamic model, so information on flow fields has to be
provided by the hydrodynamic module.
A wide range of model substances is available in Delft3D-WAQ including:
Conservative substances (salinity, CHL-aoride and up to five tracers)
Decayable substances (up to five decayable tracers)
Suspended sediment (up to three fractions)
Nutrients (ammonia, nitrate, phosphate, silicate)
Organic matter (subdivided in a carbon, nitrogen, phosphorus and silicon fraction)
Dissolved oxygen
BOD and COD (respectively Biological and Chemical Oxygen Demand)
Algae
Bacteria
Heavy metals
Organic micro-pollutants
Delft3D-WAQ allows the specification of an even wider range of physical, (bio)chemical and
biological processes. These processes are stored in the so-called Process Library from which any
subset of substances and processes can be selected. These processes include, for example:
sedimentation and resuspension, reaeration of oxygen, Algae growth and mortality, mineralisation of
organic substances, (De)nitrification, adsorption of heavy metals and Volatilisation of organic micro-
pollutants.
The D3D-WAQ module is based on the mass conservation law. The model reproduces the mass
balance of selected state variables. It does this for each computational cell. The mass transported by
water flowing from one cell to the next serves as a negative term in the mass balance of the first
computational cell and as a positive term of the second computational cell. By combining
computational cells in one, two or three dimensions each water system can be represented. In
particular the substances can be transported through the computational cells and hence through the
water system. Delft3D-WAQ solves
Eq. (7.4)
for each computational cell and for each state variable
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