WEAP can model the concentration of water quality constituents in a river using simple mixing and assuming conservative behavior, or with first-order decay and built-in BOD, temperature, and DO models, or by linking to QUAL2K. To indicate whether simulation of water quality parameters is desired, go to the Data View and click on River under Supply and Resources. Clicking on the Water Quality Category will access a window where you can select rivers for which you want to simulate water quality parameters. For instance, you may choose to model water quality only on the main river but not on its tributaries. Here, you can also enter data for BOD, temperature, and other water quality constituents determined by the user -- these data pertain to the headflow for a river. If you choose not to model water quality in a river, a concentration or temperature input here will be used as a value for the outflow of the river.
If you want to model water quality in a river, check off the box on the "Model Water Quality?" tab. In order to model water quality, you will also need to enter data on headflow (see "<Constituent> Concentration" below), groundwater and other surface water inflow concentrations, reservoir outflow concentrations, reach lengths, flow-stage-width relationships and temperature (for the BOD model). For example, you may choose to model water quality in only the main stem river, but not in its tributaries. In this case, check off "Model Water Quality?" for only the main river. Note: If linking to QUAL2K, every river in the QUAL2K data file (.q2k) must be linked to a WEAP river, and those WEAP rivers must have "Model Water Quality?" turned on, and all WEAP rivers not linked to QUAL2K must have water quality modeling turned off.
For rivers that you have selected for WEAP to model water quality, enter the concentrations of each constituent in the headflow. This will serve as the initial condition for water quality in the river.
Alternatively, for any tributaries that WEAP will not model (the box for "Model Water Quality?" is not checked) but that flow into other rivers that WEAP will model, enter the concentration of each constituent in the tributary's outflow.
Entered on: Data View, Branch: Supply and Resources \ River \ <River Name>, Category: Water Quality, Tabs: Model Water Quality?, <Constituent> Concentration