Page Comparison

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The farm dam information is on the default interface of the farm dam editor (Figure 4). The parameters Dam Capacity, Max. Dam Surface Area and Initial Storage Percentage in Figure 4 are self-explanatory. Other parameters are described below.

• Diversion Fraction - diverted flows are not included in the water balance calculation. This parameter indicates how much of the upstream inflow , is 'diverted' to pass though the farm dam and will be included in the water balance calculation for the node. The remaining water will be diverted directly re-directed (through bypass) to the downstream flow.
• Dead Storage Volume (/Dead Storage Proportion) – is the volume of the farm dam stored below the level of the lowest outlet (the minimum supply level). The demand and release requirements cannot access this water, but the natural loss (e.g. evaporation, seepage) in this water still occurs. Dead Storage Volume can also be input as a percentage or proportion of Dam Capacity by ticking the Use Proportion checkbox. The parameter name will change to Dead Storage Proportion when the Use Proportion checkbox is ticked.  The user can click on the %/proportion button to swap the type between percentage (%) and proportion.

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• Release Volume - defines the voluntary water release requested from the farm dam. The volume(s) can be entered by three types: (a) from a value, (b) from Data Source, which normally is a time series and (c) from the function.

• The Release Volume is also greater or equal to zero. If the entered value is negative, the running error will occur (Figure 7). The user then needs to fix this issue.

• Dam Surface Area Options - provides three options for the dam surface area during the water balance calculation:
  • Constant dam surfaces area using ‘Max. Dam Surface Area’ parameter – The entered constant value of Dam Surface Area is used in water balance calculation such as converting rainfall and evaporation from the depth to volume in the farm dam storage.
  • Allow dam surface area to vary according to dam volume - The area will be calculated on the basis of the storage volume, default equations and parameters. The storage volume is from the beginning of the time step. The calculated dam surface area at each time step will be used in water balance calculation. Custom Equation Parameters check box is unticked.
  • Custom Equation Parameters – This function works only when the option Allow dam surface area to vary according to dam volume is selected and the Custom Equation Parameters check box is ticked. The dam surface area will be calculated based on the storage volume at the beginning of the time step, and the equation of Volume =A*Area^B.  Where A and B are input parameters from the Interface. The calculated area at each time step will be used in water balance calculation.

b. Interstation Flow

Inflows into a farm dam in this farm dam model Interstation flow is typically used in a Schematic representation of onstream farm dam functionality. Inflows into an onstream farm dam are assumed to come from two alternative sources:

(i)

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overflows from the upstream dam(s), and

(ii)

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the local flow generated by the interstation area between an upstream dam and this dam.  In a Source catchment model this local flow is contributed as local sub-catchment outflow, also known as lateral flow.

Clicking on the Interstation Flow in the left panel of Figure 4 will display the Interstation flow parameters in the right panel for the configuration (Figure 8). The parameters include Scaling Factor and Reference Timeseries Values/Data Source.  The user can select the option Values for the constant value or Data Source for a timeseries defined in Source Data Sources.

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