River Reach Water Quality Parameters

If you are modeling water quality in a river, you must enter the following data:

Distance Marker

In order to model decay within a reach, WEAP must know how long that reach is. Enter the distance marker for the top of each reach. The distance markers should be increasing as you go downstream. The first reach does not need to start with 0. Finally, enter the distance marker for the bottom of the river (the bottom of the last reach). If you leave any reaches blank, WEAP will use the relative lengths from the schematic to estimate the reach lengths. At a minimum, you must enter the distance for the top of the first reach and the bottom of the last reach. To change the distance marker unit, go to the "Rivers" tab of the General, Units screen. Note: this data is entered only for Current Accounts.

Flow Stage Width

WEAP uses a flow-stage-width function to derive the velocity (e.g., m/s) of a stream from its flow rate (e.g., m^3/s). Using the FlowStageWidthCurve function, you will enter data points relating flow to stage (depth) and width. The "FlowStageWidth wizard" will facilitate data entry. The wizard will calculate the corresponding velocity at each data point, which is useful as an error check, since the velocity will generally (but not always) increase as the flow rate increases. WEAP uses linear interpolation to determine stage and width between data points, using trapezoids to calculate the cross-sectional area of the channel, and linear extrapolation to calculate stage and width for flows greater than the highest flow data point entered.  Velocity (m/s) is calculated for each data point as the flow rate (m^3/s) divided by cross-sectional area (m^2).  The velocity at flow rates between the data points is a linear interpolation of the velocity at the data points.  If the characteristics of a reach are similar to the reach above, you can leave it blank and it will use the FlowStageWidthCurve from the reach above. To change the stage and width unit, go to the "Rivers" tab of the General, Units screen. This data is entered only for Current Accounts. Note: If you are using QUAL2K to calculate water quality, you do not enter flow-stage-width data in WEAP but in QUAL2K.

Water Temperature

If you have chosen to model BOD and DO but have chosen not to model river water temperature (the method for the temperature water quality constituent is "Temperature (Data)"), you will need to enter the water temperature for each reach. WEAP will use values from the immediate upstream reach if you leave this value If you are modeling BOD, you must enter the water temperature of each reach. To use the value from the upstream reach, leave blank.

<Constituent> Concentration

For reaches on which you have specified Surface Water Inflow, enter the concentration of each constituent.

Entered on: Data View, Branch: Supply and Resources \ River \ <River Name>, Category: Water Quality, Tabs: Distance Marker (Current Accounts only), Flow Stage Width (Current Accounts only), <Constituent> Concentration