Rivers and creeks have natural patterns of high and low flows, which plants and animals rely on at different times to reproduce and survive. These patterns can be disrupted by human activity and climate change, with damaging effects for wildlife.
Disruption to river flows
The natural flow patterns of rivers and creeks can be disrupted by human activity, for example:
- people and businesses using river water
- dams built to provide drinking water
- land being built on, changing the way water runs off surfaces and into rivers
- pumping groundwater found beneath the earth's surface, often between saturated soil and rock crevices – this reduces the amount of water that would otherwise flow into rivers and wetlands
Climate change is also altering the amount of rainfall rivers receive.
All of these factors can affect the shape of the river, its chemical make-up and the amount of water available. This causes problems for plants and animals as:
- their habitats can shrink or become disconnected from other habitats, preventing natural migration behaviour for example
- the flows that certain species rely upon to trigger their breeding or migration may disappear
- ecosystems (communities of plants and animals in their habitats) become unbalanced, disrupting the way plants and animals support each other and potentially damaging the health of that ecosystem
Our role in managing river flows
We investigate the plants and animals that live in rivers and find out what conditions they need. We study the amount of water and its quality, and find out what local people and businesses need from the river. This information tells us:
- how much water can be taken out of the river for use by people and businesses
- how much water should be put back
- at which times it is appropriate to take or release water
We also investigate rivers and wetlands that rely on groundwater to support the plants and animals that live there. We call these ‘groundwater dependent ecosystems’, and are working with organisations who can help us manage them.
Water taken from rivers
We manage the water that is extracted from rivers in the Yarra catchment and the lower Maribyrnong. Other areas in the south of Victoria are managed by Southern Rural Water.
The main ways we manage this are with:
- diversion licences – allow people to take and use certain amounts of water from a river or creek under specific conditions, such as farmers who need to irrigate their crops
- stream flow management plans – specify how water is shared in areas with high demand for water and where the environment is at risk
- bulk entitlement agreements – place conditions on how water companies take and use water, and how much must be provided downstream of a reservoir to maintain river health
- local management plans – set the minimum flows needed in areas where a stream flow management plan is not necessary, and are implemented by both Melbourne Water and Southern Rural Water
Learn more about diversion licences, stream flow management plans and local management rules for your area:
Releasing water into rivers
Some water is set aside for the environment to protect water ecosystems, including their biodiversity, water quality and the natural processes they support. This amount is called the 'environmental water reserve' or the environment’s share of water.
The environmental water reserve includes two types of water:
- run-of-river flow, groundwater or water that is held in storage and released into a river for specific environmental reasons, such as triggering fish spawning or providing habitat during drought (environmental entitlements)
- water available because of rules on how it can be used – including conditions on bulk entitlements and water licences, management plans and limits on water use.
An environmental entitlement is the right to use water for environmental purposes, granted to the Victorian Environmental Water Holder (VEWH). In our region, the VEWH and Melbourne Water plan and manage these entitlements.
The VEWH considers the Seasonal Watering Proposals received from Melbourne Water and all of the other waterway managers across the State. The VEWH then deliver a Victorian seasonal watering plan outlining how water should be used in each of the Entitlements for the coming year.