- Further updated on 27 January 2012
- Updated on 23 January 2012
Surface water sustainable diversion limits (SDLs) have been the focus of a lot of interest both before and after the release of the draft Basin Plan. However, discussion has grown around the matter of groundwater.
This is partly because of the Commonwealth Government’s announcement of an interim Independent Expert Scientific Committee to advise governments about coal seam gas and large coal mining approvals where they have a big impact on water. This committee will also oversee research about water resources and coal seam gas/mining and fund water assessments for priority regions. The Commonwealth has also said that it will put in place agreements with the states to make sure they consider the committee’s advice.
So what part do we play in all this? As well as setting the SDLs for surface water, the MDBA sets SDLs for groundwater. However, we don’t say how that water can be used – that’s an issue for the relevant state government. Any new activity, such as mining or coal seam gas mining, is subject to state – and, where relevant, Commonwealth – planning approval.
The Groundwater SDL
In the draft Plan, we put forward for consultation a basin-wide groundwater SDL of 4,339.6 GL. Currently, up to 2,352 GL can be taken from the Basin (referred to as the ‘baseline diversion limit’). Across the Basin, the proposed total groundwater SDL is approximately 0.1% of the total amount of groundwater in the Basin. The amount of groundwater in the Basin is huge!
In deciding the groundwater SDL number, we looked at the amount of water that is ‘recharged’ (i.e., naturally replenished) to each aquifer. We then looked at the long-term ability of water to be taken from the aquifer, groundwater-dependent ecosystems, groundwater flowing to surface water and groundwater quality and used all of that information to assess the level of risk involved in taking groundwater. Based on this, we chose to make only a proportion of the total recharge available for use – that proportion is the SDL.
Developing the SDL
In developing the groundwater sections of the draft plan, we’ve been working with the state governments. The states gave us updated information on current levels of groundwater entitlements, stock and domestic use of groundwater and SDL area boundaries. We’ve also received a lot of monitoring information from the states during the development of the draft. The states also provided science about new groundwater models, recharge estimates for a number of areas and the varying connectivity between surface and groundwater.
This more detailed information played an important part in developing the new SDL. Although we have taken into account more aquifers, it’s more complicated than that. Put as simply as we can, the main reasons for the proposed change are:
- New aquifers – 304.5 GL
- Improved information on current levels of extraction – 412.3 GL
- Improved assessment of the extent to which aquifers could sustain additional extraction – 1,497.3 GL
- Adoption of existing state-based reduction schemes – 94.9 GL
Related parts of the Basin Plan
Under the Basin Plan’s Monitoring and Evaluation program, we’ll monitor groundwater extractions and aquifer levels to ensure the sustainability of the Basin’s groundwater.
For those concerned about how the use of groundwater will change surface water quality, the Basin Plan also includes a Water Quality and Salinity Management Plan. The overarching objective of this is to maintain appropriate water quality (including salinity levels) for environmental, social, cultural and economic activity in the Basin.
One quick, final note: people have a lot of questions about Great Artesian Basin water use. However, under the Water Act 2007 (Cth), we cannot manage the water in the Great Artesian Basin.