Drainage and Utilities V8i can perform water quality modeling using the SWMM water quality solver. In order to make a water quality run choose the SWMM5 Explicit Engine from the Home > Calculation Options > Active Numerical Solver.

You must then define the pollutant being modeled using the Analysis > Components > SWMM Extensions > Pollutants dialog (see ”Pollutants Dialog Box’). In the Pollutants dialog, the enter a name for the pollutant and define the properties.

If water quality data is present in a scenario, water quality calculations will be performed.

There are two methods for loading pollutants in a water quality simulation.

1. Point (node) load, which involves assigning a pollutograph (see ”Adding Pollutographs to a Node’) to a node element (such as a manhole or a cross section). This can be done in the element property grid or under the water quality alternative of the Alternatives Manager for that element. This method is used for point loads such as industrial dischargers or normal domestic customers.

2. Catchment runoff, where the pollutant enters the system based on one of several different washoff functions for each land use assigned to a catchment. Land uses and washoff (and optional buildup/treatment) functions are defined under Components > SWMM Extensions > Land Use. Then under, Analysis > Alternatives > Water Quality > Catchments, define what fraction of the catchment is associated with each land use (see ”Land Uses Collection Dialog Box’) and the initial buildup of pollutants (see ”Initial Buildup Collection Dialog Box’) at the start of the run. In long-term runs, you can specify the rate at which pollutants build up on the catchment surface (and are possibly removed by treatments such as street sweeping).

It is not possible to view the water quality results using the standard graphing. Instead, you must open the property grid for the element, scroll down to Results > Pollutant and open the collection by clicking on the ellipsis button. This will display a graph of concentration vs. time. Switching to the Data tab will give tabular results.

An overview of the water quality modeling process is shown below.