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Environmental watering maintains, and where possible, improves the health of rivers and wetlands to benefit the plants and animals that depend on them. It delivers water to mimic some of the flows in rivers and the wetting and drying patterns in wetlands that would have happened naturally before rivers were regulated.

The benefits of different environmental flows in rivers

Rivers thrive with a combination of different environmental flows, with each type of flow achieving different purposes at different times. Flow variability is one of the keys to healthy rivers. The illustration here demonstrates why: different flow types – flowing at different heights and speeds – provide diverse benefits for plants and animals in a waterway.

Types of flows

Image shows a cross section of a riverbank with different flow definitions labelled. These include overbank flow, high flow, fresh, low flow and cease to flow. Overbank flows are important to water floodplain trees and improved soil quality on the flood plain, low flows keep riverbed and lower banks wet and create pools of slow moving water, freshes prompt fish to spawn, and high flows wet stream benched and water vegetation. Rivers cease to flow from time to time and this is an important part of the natural flow regime – environmental water can provide refuges during cease to flow.
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Importance of flows

Rivers need a variety of different water heights, created by flows, throughout the year to be healthy.

How much water for the environment can be delivered is limited in modified river systems where water is held upstream in storage dams, and is used for households, industry and farms.

Delivering environmental flows may be limited by:

  • how much water for the environment is available
  • structures (such as dams, weirs, levees and low-level bridges) physically limiting where water can travel
  • overbank flows posing a flooding risk to private property.
    • water for the environment will only be delivered on private land with permission from landowners.

Water for the environment managers aim to achieve the best environmental outcomes possible within these limits.

Environmental watering improves rivers and wetlands

Rivers

In rivers water for the environment often seeks to mimic some of the flows that would have happened naturally, before dams, weirs and channels.

This is vital for the ecological health of rivers.

Water for the environment managers may look to deliver small and medium-sized river flows critical to the life cycles of native plants and animals. These flows can move sediment and nutrients through rivers, connect habitats, trigger breeding events and improve water quality.

Releasing the right amount of water into rivers and wetlands at the right time of year, for the right length of time, supports native plants and animals. For example, fish such as the threatened Australian grayling rely on an increase in river flow in autumn to signal them to migrate downstream to breed.

Wetlands

Many wetlands are now artificially disconnected or are unnaturally permanently connected to rivers or channels. This means that some wetlands don't get enough water, and others get too much and rarely get to dry out a bit like they would naturally.

Water for the environment can aim to mimic more natural wetland wet and dry cycles that plants and animals depend on. This can include environmental flows being delivered using infrastructure such as pumps, channels and regulators (devices that control water flow). Watering with works aims to limit decline by maintaining environmental condition between less frequent connecting overbank events.

Naturally, some wetlands would always have been wet, some mostly wet with some dry phases, and some mostly dry with wet phases. The frequency, extent and duration of the wet or dry phases varies from wetland to wetland, depending on where they are on the floodplain.

By mimicking the wetting and drying phases that happened naturally water for the environment managers aim to provide the variability that is one of the keys to healthy wetlands.

Like rivers, the aim of environmental watering is to protect plants and animals and generally improve the health of modified wetland.

Wetland - wetting phase

Image depicts a wetland in a wetting phase with animals and vegetation. During a wetting phase adult frogs use wetlands to lay eggs, waterbirds nest and breed, young trees establish on the banks while adult trees drink, aquatic plants grow providing habitat for waterbirds. Fish move from rivers to wetlands as wetlands fill to breed and feed, floodplain wetlands provide nursery habitat for juvenile native fish, fish return to rivers as wetlands dry.
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Wetland - drying phase

Image depicts a wetland in a drying phase with animals and vegetation. During a drying phase the receding waterline provides opportunities for wading waterbirds to stalk fish and insects, microscopic animals lay eggs that will remain in the sediment until triggered to hatch by wetland filling, trees use drying phase for seed germination and establishment and have a break from ‘wet feet’, semi aquatic plants grow providing diversity of habitat, and soil productivity is improved.
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Complementary waterway management actions

It takes more than water for waterways to be healthy. Pest management, restricting stock access, revegetation, erosion control, returning logs to rivers for fish and bug habitat, and installing fishways to allow fish to pass through dams and weirs all complement environmental watering.

Image depicts a farmland and waterway scene with complementary waterway management activities shown in use together. The activities include water troughs for livestock, weed control, revegetation for habitat and to prevent erosion, logs for fish and bug habitat, fencing to protect riverbanks from livestock, screens to help fish safely navigate channels, pest control, fishways, instream vegetation.
Example of complementary waterway management activities
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Page last updated: 05/12/24