For the first time, under the Basin Plan, limits have been set on the amount of groundwater that can be taken from the Murray–Darling Basin. This limit is called the sustainable diversion limit (SDL) and across the Basin, the total has been set at 3,334 GL/yr.
The groundwater resources in the Basin have been split into 23 groundwater water resource plan areas, which are further divided into 66 SDL resource units. These resource unit boundaries were determined using state planning boundaries.
There is a SDL volume for each resource unit.
We used a consistent assessment in setting the limit and looked at the effects of use on:
- ecosystems reliant on groundwater
- relationship between surface water and groundwater
- the ability of aquifers to continue to be productively used for a long time
- water quality and salinity.
The current average groundwater use across the Basin is 1,375 GL. In setting the limit higher in the Basin Plan we made sure enough water is available for future uses. The upper Condamine alluvium is the only groundwater resource area where the Basin Plan has prescribed a reduction in the SDL.
However, the groundwater limit isn't a target to reach. Difficulty accessing the water and poor quality restricts groundwater use making it unlikely the upper limit will ever be exceeded.
Ensuring sustainable use of groundwater
The sustainable use of groundwater is vital to ensuring the health of the Basin. To make sure groundwater use is within the sustainable limit, Basin states monitor how much water is being used.
Unlike surface water, groundwater resources take longer to respond when water is taken. The time it takes for the resource to respond depends on the type of groundwater resource and the volume of recharge.
Maintaining groundwater health
At a Basin scale the biggest risks to the health of groundwater resources are:
- reduction in the productive base — the ability for water to continue to be extracted from the aquifer
- salinity increases brought on by overuse.
We work with the states to monitor the Basin's groundwater resources to make sure they are healthy and productive. Groundwater resource monitoring looks at changes in the water level or pressure in an aquifer.
This tells us:
- the amount of water that can be easily taken — declines in flow rate from production bores can indicate a reduction in the productive base of the aquifer
- the amount of water in aquifers.
We also monitor salinity levels in certain aquifers.