Each Bulk Entitlement Order spells out a whole pattern of environmental flows that are required downstream of a reservoir – from how long they last, to how frequently they flow and how large they are.
Environmental flows are designed to mimic the natural conditions of rivers. It is not just about the amount of water but also the timing and quality. In each order, environmental flow requirements are low during the summer and autumn, and are much higher during winter and spring.
Environmental flows are vital to supporting the river’s ecological processes. High flows provide triggers for fish breeding and supply water for fish passage, so that they are able to move up and down rivers to appropriate habitat. They also keep estuaries open and provide recreational opportunities. Low flows in summer maintain fish refuges and connect habitats. Spring floods regenerate wetlands and floodplains and replenish the river channel.
To make sure that we comply with the rules about passing environmental flows, we:
- perform random checks at points along rivers, to ensure that customers are taking only the amount of water they have ordered
- maintain a number of gauging stations with alarms that alert us of unusual changes in water levels.