Ecological water requirements

Ecological water requirements (EWRs) refers to the flow regime (quantity and timing of flows) as well as the water levels and water quality required to sustain water-dependent ecosystems.

Supporting ecological water requirements is a key component of environmental water planning, which is where the department manages water to enable economic and social uses while protecting environmental values.

Understanding the requirements of species to complete their life cycle (or life history requirements) is one of the central components of determining EWRs.

In its simplest form this means protecting habitat – both ensuring that habitat of sufficient quality exists and that species have access to it at the right time.

See our biodiversity pages for habitat requirements of our water-dependent species.

Understanding flow-ecology relationships

The interactive graphic below shows a typical hydrograph for south-west rivers (wet winters and dry summers). It identifies the critical ecology-flow relationships – such as the importance of peak winter flows to flush sediment and nutrients through rivers, or to connect habitats along a river and with the floodplain.

When environmental water planners assess risk of certain applications to take water, they are considering how this will affect each of these ecological end-points. This is a complex process as it needs to consider difference between and within systems, for example, other changes that may be occurring in a catchment due to land uses or climate.

Identifying aquatic animals and understanding status of habitat quality and connectivity (information provided through the Healthy Rivers' assessments) is critical to underpin this process.

An ecological-flow model for south-west Western Australia


Hover over the diagram to learn about the different elements of flow-ecology relationships in south-west rivers