Versions Compared

Key

  • This line was added.
  • This line was removed.
  • Formatting was changed.
A Confluence node represents a natural join in a river system (a tributary or reconnection of an anabranch). Both inflows combine into a single effluent without any loss or delay. The behaviour of a confluence node depends on the number of branches that are regulated. You can describe the arrangement of the natural system as one of:
  • Neither branch is regulated - no configuration is required as there are no orders;
  • One branch is regulated; or
  • Both branches are regulated.
Info
iconfalse
Note: The confluence node adds the upstream minimum and maximum constraints together.

One regulated branch

If there is only one regulated branch, the unregulated branch behaves like an inflow node. As there is only one regulated upstream branch, priority setting is not required. In this case, the confluence node can be thought of as acting in a similar manner to an inflow node.

Info
iconfalse
Note: The names in the Link column are those you assign to the upstream links.

As such, the branch which is unregulated needs to have forecasting ability of the inflow arriving, so that orders may be adjusted for the expected inflow. Therefore the confluence node has a forecasting model attached to it (as shown in Figure 1). The forecast model is the same as that available for an inflow node (see Forecasting inflows). However, you cannot choose to use a model based on the current time-step.

Info
iconfalse
Note: The confluence forecast model ignores any upstream nodes on the regulated branch. This means that any upstream inflow node forecast models are ignored in the confluence node forecast calculation.

 

Figure 1. Confluence node (Single regulated branch)


 Both regulated branches

 If both branches are regulated, orders are processed according to the method specified you have to define how orders may be split by choosing one of two methods specified under Regulated Ordering Methodology:  

  • Constraint based (default) - Specify a priority for each branch. Click the cell in the Priority column and edit the value; or
  • Harmony based - Used to balance the volumes of defined storages on each upstream branch in a defined ratio. You must specify As shown in Figure 2, you must define the upstream storage volume for each upstream branch on which to base the harmony operations. These are defined by the Function Editor, so that potentially each branch’s volume can be sourced from multiple storagesbranch using the Function Editor (in the Branch Setup table). You must also specify how to split the upstream orders (under Harmony Ordering Setup) - using either a table or an expression.
When defining a table that
  • :
    • A function that defines the proportion for splitting the orders to each upstream branch based on model parameters; or
    • A table that has the proportional relationship on how orders are to be split upstream based
on
    • upon the defined volume of water up each branch for each owner
as shown in Figure 2. You
    • .

You can work with the table as follows:

  • To add a column, right click on one of the column headings and choose Add Volume. The other menu options will change the columns as shown in Figure 2; and
  • To add a row, click on a cell in the last row to highlight and edit it. Enter Input a value and press Enter.
Figure 2. Confluence node, harmony based

Image Modified
The names in the Link column are those you assign to the upstream links. For systems with a single regulated inflow, it is possible to define a method to forecast inflows from the unregulated system. In this situation, you select the row representing the unregulated link, after which you can adjust the Recession Forecast Model controls.

Info
iconfalse

Note: You may have to select the regulated link and then re-select the unregulated link before the forecasting controls become visible.