Links represent a physical entity or process within the system, but one that incorporates transportation from an upstream node to a downstream node. Stormwater pipes, channels and sewer mains are all examples of entities represented by links.
The Urban Developer Plugin currently does not support routing of flows. Inflows are directly translated to outflows, ie links do not store or route water.
You can only connect nodes using links. You cannot connect two links to each other without an intervening node.
Urban Developer attempts to simplify the model setup process and prevents conceptual mistakes such as connecting a node input to a node input, or an output to an output. There are restrictions on which node inputs and outputs you can connect together. See Node Connection Rules.
A demand link supplies a requirement for water to be met from the sources in the urban water system. Demands may be consumptive or non-consumptive and may, for example, include town water supplies, irrigation, hydro, industrial, minimum flows, environmental and recreational requirements, and interbasin transfers, but need not be limited to these.
Some Urban Developer nodes have demand link outputs, as they supply a requirement (eg mains supply), and other nodes have demand link inputs (eg Water Use).
A wastewater link conveys water which has been used at least once and hence is regarded as unsuitable for immediate reuse for that purpose without treatment; water collected from domestic and industrial sources to be treated prior to discharge to the environment or for recycling for other uses.
Certain Urban Developer nodes have wastewater outputs. For example, the Wastewater Connection node collects, or aggregates, individual flows into a combined waste water flow. Other nodes have wastewater inputs. The Junction node acts as a collector of different flow types (wastewater, runoff, etc). (Wastewater Connection and Junction nodes area not currently available in the Urban Developer Plugin).
Stormwater links convey sudden, excessive run-off of water following a storm. Surface runoff results from excess rainfall, usually passing quickly through a drainage area.
The detention outflow of a Tank node is an example of an output feeding in to a stormwater link. Stormwater links can feed into Wastewater nodes, Pervious Area nodes, and Junction nodes. (Wastewater, Pervious Area and Junction nodes area not currently available in the Urban Developer Plugin).
Runoff links convey flow from a given area; the flow results from the effects of rainwater and/or applied irrigation water in excess of any demand.
Examples include Roof nodes, which have runoff link outputs, and Pervious and Impervious Area nodes, which have runoff link inputs. (Pervious and Impervious Area nodes area not currently available in the Urban Developer Plugin).