Introduction
The Environmental Demand Model (EDM) in Source operates on a daily basis generating demands and extracting water to meet these demands using the environmental demand and supply point node. This model is used to define environmental water requirements at the project set up phase and then applies a series of heuristic routines in order to define the water required to achieve the specified environmental water requirements. It can be applied in both regulated and unregulated systems.
The EDM is designed by default to represent an environmental flow requirement at a specific location within a river system. Environmental flow requirements may generally be classified as either in-stream (refer to In-stream requirement) or floodplain requirements (refer to Floodplain), where the former creates flow conditions that remain within the river channel, and the latter creates flow conditions that spill over bank. How these situations are configured in Source is largely dependent on the conceptualisation used to model the interaction between the channel and the floodplain.
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| The In Source, the EDM is modelled using the environmental demand node in Source. Refer to Environmental Demand node for details on configuring the node. |
In Source, the environmental demand node is used to model environmental demand, which can be set up in two ways:
- As an in-stream requirement (In-stream requirement); or
- To act as a floodplain (Floodplain).
Further detail about the node's configuration is described in their respective links shown above.
Table 1 Table 1 shows the Commonwealth Environmental Water Holder Framework, which determines environmental watering actions whereby watering options for a specific asset are a function of water availability.
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The following assumptions are made when EDM is configured in Source:
- Water requirements are not additive - A basic assumption used in the EDM is that environmental water is not consumed and, as such, flow rule water requirements for more than one environmental asset can potentially use the same water in accounting for the success of their flow rules being met. For example the minimum flow requirement for fish passage is not necessarily a separate parcel of water from the minimum flow required to prevent an algal bloom;
- Flow rules can be co-dependent: A flow rule can be conditionally contingent on another flow rule also being met;
- Flow rules should only be attempted if their requirements are likely to be met: The EDM determines the daily demand, however before passing the demand for this day, the EDM checks to see if the total water required to complete the rule is available; and
- The highest priority environmental water demand is for environmental flow rules which have commenced but not yet completed. If an environmental flow rule has started to be met, then the continuation of meeting this flow rule requirement has precedence over commencing water ordering to meet a new flow rule.
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