The key water legislation in NSW – the Water Management Act 2000 – recognises the need to allocate and provide water for the environmental health of our rivers and groundwater systems. The Act provides water for the environment in two ways: planned environmental water and adaptive environmental water.
Planned environmental water
Planned environmental water is water prescribed under the rules of a water sharing plan
Rivers and streams
To be healthy and reproduce successfully the plants and animals that live in rivers and streams need floods (very high flows), freshes (high flows) and dry spells (very low flows).
The environmental rules in surface water sharing plans are commonly referred to as environmental flow rules. These rules are designed to ensure the plants and animals in streams continue to experience all these different types of flow events.
To do this the plans for regulated rivers (those rivers with major storages in their headwaters) include rules on the timing of releases from storages, and the volume of flows required at specific sites.
For unregulated rivers (those whose flow is not controlled by major storages) environmental flow rules typically involve cease to pump rules and commence to pump rules. Cease to pump rules ensure that very low flows are protected by requiring users to stop taking water when flow declines below a set level. Commence to pump rules ensure that freshes are available to the environment by requiring users only recommence taking water once flow has increased above a specified level.
In groundwater systems the environmental rules in the water sharing plan are designed to protect the aquifer and its groundwater dependent ecosystems.
Aquifers can store large volumes of water, often accumulated over thousands, or even tens of thousands of years; this is referred to as 'storage'. In most groundwater sources, 100 per cent of groundwater storage is reserved as planned environmental water.
Recharge is the addition of water to an aquifer. Recharge usually comes from rainfall, surface water bodies such as rivers, or via flow from adjacent aquifers. In most groundwater sources only a proportion of recharge is available for extraction. The remainder of recharge is reserved for the environment. Limiting the volume of use to a proportion of recharge is intended to reduce the risk of unsustainable groundwater extraction in the long term.
Some groundwater sources are highly connected to surface water, so that taking water from one source affects the other. Recharge volumes change with the amount of water extracted. In these groundwater systems, environmental water may also be provided through daily access rules to ensure taking groundwater does not adversely affect surface water flows.
Sensitive environment areas
Water sharing plans also include rules on the location of new works and extraction from existing works to limit impacts on surface water base flows and groundwater dependent ecosystems.
Adaptive environmental water
In addition to planned environmental water, the Act also allows water to be taken and used for the environment under water access licences where these licences have a condition specifying they are to be used for environmental purposes. This is known as adaptive environmental water.
The water purchased under programs such as Living Murray and Riverbank is licensed in this way and is additional to the water provided to the environment as planned environmental water under the water sharing plans.