Note: This is documentation for version 4.9 of Source. For a different version of Source go to the Space Directory.
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Mass Balance

Results Manager provides a Mass Balance tool to check all of the mass flows entering, remaining in, or leaving the system. It is configurable for time period and for different parts of the model that you can choose.  Individual inputs and outputs for the mass balance are specified by the user from the results of the model run, so before starting a mass balance check, ensure that all required results are recorded. Typical recorded results used in a mass balance check could be:

  • All inflow volumes of inflow nodes, 
  • storage volume, 
  • storage rainfall volume, 
  • storage evaporation volume, 
  • storage infiltration volume, 
  • extracted water from supply points, 
  • downstream flow at the lowest point

Each inflow, storage, and outflow need to be added to the appropriate tab (Storage Start, Inflow, Outflows, Storage End).

To calculate mass balance, right click on a result set and select Statistics » New Mass Balance from the contextual menu (Figure 6). A new mass balance statistic will be created and listed under Statistics in the Custom Chart and Statistics pane, and the mass balance tool will be shown in the central workspace (Figure 6), where:

  • The lower right pane allows you to select the result set(s) and time period used to calculate the mass balance;
  • The upper right pane includes four tabs: Storage Start, Inflow, Outflows, Storage End; which will accept results listed in the upper left pane;

    Note: The Group Name column allows you to specify multiple sub areas for calculations of the mass balance report. Double click the Group Name column to specify a new group name.
  • The upper left pane lists the results from the selected result sets(s); right click on a result to add it to one of the four tabs in the upper right panel; and
  • The lower left pane is the mass balance check, which will calculate the flow from the four tabs in the upper right panel.

Note: If a result is selected for use in the mass balance, and then a result set is selected that does not contain that result, a value of zero will be assumed for the missing result.


Figure 6. Mass balance

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  1. Note that initial storage volumes must be captured by a function pointing to a model variable set to the storage volume, evaluated at the start of timestep.  Forced evaluation of the function should be set to on.


    This applies to storages and routing links.