Water Quality Constituents 

WEAP tracks water quality, including pollution generation at demand sites, waste removal at wastewater treatment plants, effluent flows to surface and groundwater sources, and water quality modeling in rivers. On the water quality constituents setup screen, turn on water quality modeling by checking the Enable water quality modeling checkbox. You may then define up to 20 constituents to track in your application. Set the scale and load unit as appropriate for entering the annual production of the pollutant by the demand site, per unit of activity. Set the concentration unit appropriate for entering data on concentrations of constituents in demand site outflows, and in headflows, reservoir outflows and groundwater outflows.

For each constituent, specify which method WEAP should use to calculate surface water quality concentrations, in the Calculate By column:

Conservative: There is no decay of this constituent--the instream concentration will be computed using simple mixing and weighted average of the concentration from all inflows.

First-Order Decay: This constituent decays following an exponential decay function. Enter the daily decay rate here.

BOD: WEAP will use its built-in BOD model to simulate the changes in the biochemical oxygen demand (BOD) in the river. In order to model BOD, you will need to include temperature as one of your water quality constituents (with unit = Celsius), and either enter as data the temperature of water in the river for each reach, or model it in WEAP.

DO: WEAP will use its built-in DO model to simulate the changes in dissolved oxygen (DO) in the river. Because the DO model uses BOD as an input, you will also need to simulate BOD.

For temperature values (required by WEAP to implement the BOD and DO modeling), one can choose one of three methods:

Temperature (Modeled in WEAP): WEAP will calculate water temperature for each river reach based on climate data (air temperature, humidity, wind, and latitude) input in the Data view (under the Climate tab for the reach).

Temperature (Data): the user specifies the water temperature for each reach. If this option is selected and temperature for a particular reach is left blank, WEAP will assign to that reach the temperature of the immediate upstream reach. Water temperature is needed by the BOD model.

Modeled in QUAL2K: Link to the US EPA water quality model QUAL2K and let it model water quality for some or all water quality constituents. See Linking to QUAL2K for details.

Note: you can use the WEAPWQConstituent API to edit the list of water quality constituents from a script.

Menu Option: General: Water Quality Constituents