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Welcome to the next generation MIKE+ Documentation

Introduction to Water Quality Modelling

MIKE+ provides several modules for the simulation of water quality for both urban catchment surfaces and sewer systems.

MIKE+ can model complex water quality and pollutant transport mechanisms using Stormwater Runoff Quality (SWQ), Advection-Dispersion (AD), and the MIKE ECO Lab engine to solve biological processes equations.

The Advection-Dispersion model can be used for calculation of the transport of dissolved or suspended substances, and for modelling of water temperature variation within the domain. The model is based on the transport equations for dissolved material. The equations reflect two transport mechanisms: the advective (or convective) transport with the mean flow velocity and the dispersive transport due to concentration gradients in the water. The main assumptions of the model are:

  • The considered substance is completely mixed within an element / cell of the 2D domain. This implies that a source term is considered to mix instantaneously within the domain’s element;
  • The substance is conservative or subject to a first order reaction (linear decay).

The Advection-Dispersion model requires two types of data: time series of concentrations at the model boundaries and data for full definition of the components to be modelled, e.g. initial concentrations, dispersion coefficients and decay rates.

The MIKE ECO Lab framework offers versatile and flexible options for water quality modelling, by describing biologicial processes on top of the Advection-Dispersion model. Water Quality simulations can be performed using either standard, predefined MIKE ECO Lab templates or user-defined templates with tailored Water Quality models.

This user guide focuses on models involving 2D overland features. Further details on water quality modelling for 1D models may be obtained from the respective user guides (i.e. MIKE+ Collection System, MIKE+ River Network Modelling or MIKE+ SWMM Modelling User Guides).

Furthermore, note that at present, couplings of water quality components between 1D and 2D models is only available for models of type ‘Rivers, collection system and overland flows’ in MIKE+. Thus, this chapter presents information relevant only for projects with models of this type.