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About Nodes
Nodes represent places where actions or measurements occur in a river system, where water can be added, extracted, stored, recorded, or
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change ownership in
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a model. A node can be used to represent things that actually happen over a large physical area but
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that, for modelling purposes, occur at a single point
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Table 16 summarises the core purpose of each of the node types in Source. Each node has distinct behaviour in both the Flow Phase and the Ordering Phase of the model and these behaviours are described in the corresponding section for each node. These sections deal mostly with water quantity. In addition, each of the nodes have some influence on the routing of ownership and constituents (where enabled). These behaviours are covered in the corresponding chapter of this document ( for Ownership, for constituents).
Table 16. Nodes in Source
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Node name
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Node icon in Source
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Description
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Refer to
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Inflow
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Defines the flow (including constituents and ownership) entering the network as a result of tributary inflows, inter-basin transfers, discharge of groundwater systems and outflows of infrastructure such as sewerage treatment plants.
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Gauge / Unaccounted Difference
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Used where there is measured flow (and/or constituent) data at some point in the river network, OR where modelled outputs are required for reporting. Gauges node can be used as comparison points, or the observed flow can be used to override the upstream modelled data for downstream. When overriding the modelled flow with observed, the gauge icon changes and the node reports the ‘unaccounted difference’ between the observed and predicted data.
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Confluence
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Represent joins in a river system, where two upstream flows are joined into one downstream flow without loss or delay. The bulk of the configuration of a confluence is in terms of influencing the passage of orders from downstream to storages upstream of the confluence. Confluences can be unregulated, where neither upstream branch contain any storages, or they can have regulating structures upstream on one or both of the branches.
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Loss
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Describe the amount of water that is lost from the stream network at a point. Loss relationships can represent physical processes, such as transmission losses, or they may be used to represent measurement error in the input data for the model.
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Maximum Order Constraint
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Used at points in the network where a physical or management constraint exists to prevent regulated flows exceeding a certain threshold. These thresholds can be expressed as a constant (typically to represent a physical constraint, such as a choke point) or as a variable constraint using an expression (typical for management constraints). Where the orders originating downstream of the constraint are above the current threshold, the orders are reduced.
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Minimum Flow Requirement
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Used to maintain a specified minimum flow at a point in the network. Where the orders originating downstream of the Minimum Flow Node are less than the minimum, additional orders are placed in order to meet the threshold. Minimum flows can be specified as a monthly pattern, a time series, or an expression.
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Off Allocation
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Used to determine how much off-allocation flow is available in the river (at the node), as well as how to share this between the downstream water users that have licence shares. Off-allocation flows are those that are in excess of regulated requirements.
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Parallel Arcs
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Used to specify costs on a particular supply path, in order to influence the distribution decisions in NetLP mode.
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Splitter
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Used where the network divides into two, such as major anabranches. Splitters can represent control structures, in which case the water going down each of the links is a management decision, or uncontrolled branches, where the water going down each links is a function of upstream flow alone.
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Storage
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Used to hold water at a point in the network. Storage Nodes are used for various types of water bodies, including major reservoirs (on river and off river), weir pools and urban lakes. Storage Nodes can capture much of the operating details of regulating water bodies, such as release structures and operating rules, as well as physical properties such as surface area relationships for evaporation, rainfall and groundwater.
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Supply Point
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Are points in the stream network where water demands are represented for the purposes of either extraction (for consumptive use) or for in-stream use. Supply Points are coupled to a single Water User Node, which calculates the actual demand, noting that a single Water User Node can make use of multiple Supply Point Nodes in order to place demands in multiple parts of the system.
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Transfer Ownership
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Used to reassign the ownership of water instream at a point in the network, such as reassigning an owners water when the water flows past the last opportunity that the original owner had to extract the water.
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Water User
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Represents the actual demands (consumptive or non-consumptive) in the system. Water Users can model demands by way of several alternate demand models, and then seek to have these demands met either by localised storage, or from one or more Supply Points. The demands can be distributed between these sources, either by a set of user specified rules, or by way of a Resource Assessment System.
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Wetland Hydraulic Connector
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. In sub-catchments, they provide a position in the catchment network where water management information can be placed. In Source, nodes are depicted using the icons shown in Figure 1.
Figure 1. Node icons for Source
Using nodes in Source
This section outlines how to work with nodes in Source. Some actions can be duplicated for links.
Adding nodes in a model
To add a node to a model, either drag the appropriate type of node from the Node Palette and drop it onto the Schematic Editor, or right-click on the Schematic Editor and choose the appropriate node from the Add menu.
Node and link default names
Whenever a node or link is created, it is given a default name in the pattern:
type #
where "type" is the type of node or link and "#" is a number which increases monotonically during the life of the schematic.
Node connections
Nodes can be joined to each other according to the matrix in Figure 2. Links between nodes will vary depending on the nodes being connected. For example, a wetland conveyance link will occur when a storage node is linked to a wetland connector.
Figure 2. Node connection matrix
Renaming nodes and links
Changing the name of a node or link only alters it in the scenario that you changed it in. A change in one scenario does not propagate to others; they are not linked in any way. You can change the name of a node or link using one of the following methods:
- If the Project Explorer is not visible, make it visible either by choosing View » Project Explorer or by clicking its equivalent on the toolbar. In the Project Hierarchy, click the node or link to select it, pause, and click a second time. The name will be prepared for editing (Figure 3 ). Type the new name and press return; or
- Right-click the node or link in the schematic and choose Rename. The name will be prepared for editing. Type the new name in the field, then press return.
Figure 3. Renaming a node or link
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Note: Source does not support duplicate names for nodes or links and will warn you if there is one. You must ensure that the names you choose are unique to the scenario (schematic). |
Editing nodes
Use the feature editor of a node to change the parameters associated with them. To open a feature editor you can either double click on the node icon, or right click on the icon and select Edit.
Searching for nodes and links
The Find panel in Source allows you to search for specific nodes and links within open scenarios. Press Ctrl+F to open the Links panel (Figure 4) and enter the search term. The result set indicates the scenario containing the node/link along with its type. This is useful when you are working with very large scenarios.
Figure 4. Find panel
Copying and pasting
You can copy and paste a desired selection of nodes and/or links within the same scenario. Select the desired nodes and/or links, right click and choose Copy. To paste the selection, right click on the Schematic Editor and choose Paste. Any time-series files or settings get copied in this way.
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Note: Any expressions associated with the nodes and/or links do NOT get copied. |
Deleting nodes and links
Deleting nodes can be achieved simply by selecting the node and pressing the delete key, or by right-clicking it and choosing Delete from the contextual menu. Deleting a link removes only the link. Deleting a node removes both the node and any links that were attached to the node.
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Note: Deleting a node will cause loss of any data associated with that node, as well as any links connecting to or from it. A delete operation cannot be undone. You must recreate the link or node. |
This chapter describes how the various nodes available in Source can be configured. For details on how they operate, refer to the Source Scientific Reference Guide.
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Note: In a catchments scenario, all nodes are, by default, confluence nodes, so every node ever created will be, at least, a confluence. |