Modelling farm dams in Source using the Onstream Farm Dam node 

Create node(s) for farm dams in a Source model

The creation of a farm dam node (1) in a river system model from the Schematic Editor and (2) in a catchment model from the Geographic Editor, is different. The methods for both models are described separately below:

(1) From the Schematic Editor

The green triangle icon on the Node Palette represents the onstream farm dam. Dragging the icon from the Node Palette to the Schematic Editor interface can create a farm dam node. The accurate coordinates of farm dams’ positions are not required.

(2) From the Geographic Editor

There are two ways to add the onstream farm to the catchment model from the Geographic Editor:

a. Change an single existing model element in a Source catchment model to an onstream farm dam

The first step is to select an existing model element (e.g., a Confluence node) and right-click on it, and the context menu then will be displayed. Clicking on the menu item of Change Node Model (1 in Figure 2) on the context menu will display the additional context menu, and further clicking on the Onstream Farm Dam option (2 in Figure 2) will change the node to Onstream Farm Dam that is displayed as a green triangle icon. The user can use the menu item of Add Node (3 in Figure 2) to add a Confluence node for node model change if needed. The accurate coordinates of farm dams’ positions may not be essential.

Figure 2 Modeling Onstream Farm Dam node from Geographic Editor

b. Bulk Change Node Models for onstream farm dams:

Right-clicking on any place in the model interface of Geographic Editor will display a context menu, which includes the menu item Bulk Change Node Model (4 in Figure 2). This menu item allows the user to change a group of nodes to onstream farm dams at once. The procedure is as follows:

• Prepare a location shapefile of the nodes for the fam dams - These locations should be already used during the model building and exist as nodes in the catchment model.
• Open Bulk Change Node Models editor - Clicking on the menu item Bulk Change Node Model will show the interface of the Bulk Change Node Models editor (Figure 3). Initially, the contents in the Nodes Located box and the selected item in the dropdown list of destination node types are empty.
• Configure Bulk Change Node Models editor - Clicking on the button of Load node location shape file (Figure 3) will display the Open dialogue box, which allows the user to select the prepared location shape file. After the user clicks on the OK button on the Open dialogue box, the node names (e.g. 156, 157) in the Source model will be displayed in the Nodes Located box, and those nodes have the exact locations defined in the shapefile.  The user must select Onstream Farm Dams from the dropdown list below the Nodes Located box.
• Convert the selected nodes to destination node type – Clicking on the button of Change all loaded nodes in Figure 3 will convert all nodes in the Nodes Located box to the selected node type in the dropdown list (e.g. Onstream Farm Dams in Figure 3).
• The user can repeat the above steps to convert nodes to other types. Otherwise, clicking on the Done button can close the window.

Note that Bulk Change Node Models tool also can convert the located nodes to other types such as Supply Points, Gauges, etc. The procedure is the same as the above one for onstream farm dams, and the user just needs to select the expected node type (e.g Supply Points) from the dropdown list instead of Onstream Farm Dams.

Figure 3 Bulk Change Node Model editor

Configure Onstream Farm Dams node(s) in the Source model

There are two ways to configure the parameters of the onstream farm dam. One method is for the individual node of the Onstream Farm Dam, and another method is for all nodes of modelled Onstream Farm Dams. Two methods can be used jointly.

For an individual node of the Onstream Farm Dam

The user can use Future Editor (such as Edit in Figure 2) to set up the parameters of the farm dam. Clicking on Edit from the selected farm dam node will open the farm dam editor (Figure 4)

Figure 4 Farm dam editor – Dam Information

(1) The farm dam information

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

• Diversion Fraction - decides how much the “upstream” flow, which includes both the upstream flow and interstation inflow, will be involved in the water balance calculation in the edited farm dam. The remaining water in the “upstream” flow will be diverted directly 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 inputted as the percentage or proportion of Dam Capacity by ticking the Use Proportion checkbox. The parameter name will also be changed to the Dead Storage Proportion when the Use Proportion checkbox is ticked.  The user can click on the %/propor button to swap the type between percentage (%) and proportion.

Note that the values entered from different types (i.e., volume, percentage, and proportion) for the same farm dam cannot be automatically converted until the configuration is saved by clicking on the OK button of the Editor interface.

The Dead Storage Volume can be entered by three types of data sources: (a) from a value, (b) from Data Source, which normally is a time series and (c) from the function.

The range of Dead Storage Volume is between zero and max capacity. Ranges of the percentage and proportion will be from 0 to 100 and 0 to 1 respectively. If the entered values are not within the range, the running error will occur. The user then needs to fix this issue. The example screen of the error message (for entering -1) is shown in Figure 5. “166” in Figure 5 is the name of the associated farm dam.

Figure 5 Running error screen for unsuitable input of Dead Storage Volume

• Bypass Flow - defines the maximum capacity of the flow bypassed from the upstream flow directly to the downstream of the farm dam.

  Now Bypass Flow can be entered by four types of data sources: (a) from a value, (b) from Data Source, normally it is a time series, (c) from the function and (d) a Monthly Pattern shown in Figure 6.

Figure 6 The Editor Screen of Select Source for ByPass Flow

The Bypass Flow is designed to be greater or equal to zero. If the entered value is negative, the running error will occur. The user then needs to fix this issue. The example screen of the error message (for entering -2 for Bypass Flow) is shown in Figure 7.

Figure 7 Running error message for unsuitable input of Bypass Flow and Release Volume

• 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.

(2) Interstation Flow:

Inflows into a farm dam in this farm dam model come from two alternative sources: (i) overflows from the upstream dam(s) and (ii) the local flow generated by the interstation area between the upstream dams and this dam.

Clinking 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.

The interstation inflow is calculated based on a reference value or time series (i.e., at a flow gauge) that has been scaled down/up. If the scaling factor is 0.8 and the reference timeseries value is 0.25 ML/d, the Actual Interstation Flow (ML) is 0.2 ML/d. The scaling factor reflects (a) the interstation catchment area relative to the reference catchment area; and (b) the nonlinear relationship between the catchment area and flow.

Figure 8 Farm dam editor – Interstation Flow

(3) Seepage

Seepage from the farm dam into the underlying soil can be modelled by defining an exfiltration rate (e.g., mm/d). The water that seeps from the farm dam is lost from the catchment and does not re-enter the system downstream.

Clinking on the Seepage in the left panel of Figure 4 will display the Seepage parameter in the right panel for configuration (Figure 9). The parameters can be configured by the constant value or time series from Data Source.

Figure 9 Farm dam editor – Seepage

(4) Demand

Clinking on the Demand in the left panel of Figure 4 will display the demand parameters in the right panel for configuration (Figure 10). The demand parameters include Demand Factor and Demand Timeseries Values/Data Source.  The demand factor can be estimated from the ratio of the average annual demand of the farm dam volume.

In this farm dam model, the demand is not directly using Demand Timeseries. The demand volume is determined by the demand factor and farm dam volume, and its temporal distribution is determined by the Demand Timeseries Values/Data Source.

Figure 10 Farm dam editor – demand

(5) Rainfall

Clinking on the Rainfall in the left panel of Figure 4 will display the rainfall parameters in the right panel (Figure 11). The parameter is the rainfall to the edited farm dam, and it can be configured by constant Values or timeseries data in Data Sources.  Its unit is depth such as mm, and Source will convert it to volume by the dam area calculated as the description in section (1) The farm dam information.

Figure 11 Farm dam editor – Rainfall

(6) Evapotranspiration

Clinking on the Evapotranspiration in the left panel of Figure 4 will display the evapotranspiration parameters in the right panel (Figure 12). The parameter is the evapotranspiration from the edited farm dam, and it can be configured by constant Values to timeseries in Data Source. Its unit is depth such as (mm/day) and Source will convert it to volume using the calculated dam area as the description in section (1) The farm dam information.

Figure 12 Farm dam editor – Evapotranspiration

Clicking on the OK button in Figure 4 will save the setup of the farm dam. The Cancel button will discard the entered parameters.

For all Onstream Farm Dams nodes

Source allows inputting, editing, checking, and outputting all parameters of all farm dams together. Tool menu item Edit » Feature Table... can access Feature Table for this functionality (Figure 13). Clicking on the Onstream Farm Dam in the left panel (Figure 13) will display the existing values of all editable parameters for all onstream farm dams in the right panel.

The Feature Table headlines of all parameters are the same as (or similar to) those names described in the above section of For an individual node of Onstream Farm Dam except for seven headlines below:

• Dead Storage Set Using Proportion – This is related to the value of Use Proportion checkbox on the Interface (Figure 4). Its change in the Feature Table will decide which one, Dead Storage Volume or Dead Storage Proportion, will be editable in the Feature Table.
• Dead Storage Volume and Dead Storage Proportion - The definitions of both columns are the same as those in Figure 4. However, although both columns are listed in the Feature Table, only one column in each row can be saved. The edited values in cells of column Dead Storage Proportion will be saved if Dead Storage Set Using Proportion(s) in the same rows are selected. Otherwise, the edited values in the cells of column Dead Storage Volume will be saved. After the Feature Table is saved, the remaining cells in another column (either Dead Storage Volume or Dead Storage Proportion) will be automatically converted from the saved cells by Source.
• Dam Surface Area Calculation – which only has two values for selection: Constant or Variable. The value of Constant indicates the option of Constant dam surfaces area using ‘Max. Dam Surface Area’ parameter (Figure 4) will be used in the water balance calculation. Variable indicates the option Allow dam surface area to vary according to dam volume (Figure 4) will be used in water balance calculation.
• Is Custom Param – shows the value of the check box Custom Equation Parameters (Figure 4). Its value only works when Variable is selected in the column Dam Surface Area Calculation.
• SA-Volume EQN A Factor - the value for A Factor (Figure 4). Its value will be used only when Dam Surface Area Calculation column is Variable and Is Custom Param is ticked.
• SA-Volume EQN B Factor - the value for B Factor (Figure 4). Its value will be used only when Dam Surface Area Calculation column is Variable and Is Custom Param is ticked.

The user can directly edit all parameters from Feature Table.

Figure 13 Farm dam configuration for multiple farm dams through the Feature Table

Recorders of Onstream Farm Dam node

Some recorders for the onstream farm dam in Source are described below to clarify the difference between the similar recorders.

Migrate the Source model using the FarmDams plugin across to CORE

The onstream farm dam functionality in Source can be accessed from the plugin of FarmDamsplugin before Version V5.21 or CORE without the Farm Dams plugin after Version V5.21. Only Source projects using the Farm Dams plugin in Version 5.20 can be automatically mitigated to the project with farm darn functionality from CORE.  The users need to upgrade their old models (using the Farm Dams plugin) to Source V5.20 with the farm dam plugin first and save it as the upgraded project. The user then opens the upgraded project in later versions such as late 5.21 without the Farm Dams plugin, and the Source will autumnally migrate the farm dam functionally in the project file from plugin to CORE.