Nodes enable the modelling of actions or measurements that occur in a river system. For example water can be added, extracted, stored, recorded, or have a change in ownership. A node can be used to represent things that actually happen over a large physical area but which, for modelling purposes, occur at a single point, such as extractions from a group of off-takes.
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 ( Ownership, Water quality processes for constituents).
Table 16. Nodes in Source
Node name | Node icon in Source | Description | Refer to |
|---|---|---|---|
Inflow |
| 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. | Inflow node - SRG |
Gauge / Unaccounted Difference |
| 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. | Gauge node - SRG |
Confluence |
| 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. | Confluence node - SRG |
Loss |
| 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. | Loss node - SRG |
Maximum Order Constraint |
| 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. | Maximum order constraint - SRG |
Minimum Flow Requirement |
| 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. | Minimum Flow Requirement - SRG |
Off-allocation | 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. | Off-allocation (SRG) | |
Parallel Arcs |
| Used to specify costs on a particular supply path, in order to influence the distribution decisions in NetLP mode. | NetLP - SRGNetLP (SRG) |
Splitter |
| 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. | |
Storage |
| 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. | Storage node - SRG |
Supply Point | 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. | Supply point node - SRG | |
Transfer Ownership |
| 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. | Ownership at nodes and links - SRG |
Water User |
| 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. | Water user node SRG |
Wetland Hydraulic Connector |
| Used to connect an off stream wetland node (represented using a Storage Node), to a main channel. The Wetland Hydraulic Connector is placed on the main channel and is connected to off stream Wetland Storage Node using the lateral connections. | Wetland Hydraulic Connector - SRG |
