Research and Planning
The ACT's Murray Darling Basin Water Cap
The ACT water cap is an agreement between the ACT Government and the Murray Darling Basin Ministerial Council determining the total amount of water that the ACT is allowed to use or divert from the Murray Darling Basin.
A water cap is the agreed way to assist all users of water in the Murray Darling Basin in having access to a fair volume of water, and to help ensure there is sufficient water flowing in the system for its long term health. New South Wales, Victoria, Queensland and South Australia all operate under a cap as required under the Murray-Darling Basin Agreement.
How much are we allocated under the cap?
The agreement currently allows the ACT to take out of the rivers, a net 40 GL (gigalitres) of water per year.
This means for example, in an average year (without water restrictions) the ACT takes approximately 70 GL from the rivers (65GL for drinking water purposes and another 5GL for other uses). Of this water, approximately 35 GL goes through sewage treatment systems where it is treated to a high level before being discharged back into to the river system. This means the ACT's net use from the Murray Darling Basin is only 35 GL.
Is this enough water for the ACT in future?
The 40 GL cap is currently enough water for the ACT to use sustainably.
The amount of water allocated to the ACT grows as the population increases.
The amount allocated to accommodate each new person is calculated on per person water consumption figures at that time, and is discounted by 25% to reflect water reduction targets set in the ACT Government's Think water, act water strategy.
So there is sufficient water for the ACT under this cap into the future, if we continue to use it sustainably.
What conditions apply to the cap?
A number of conditions apply to the cap. They are that:
- The ACT may purchase additional water from interstate and sell it if it is not required, but cannot sell unused water from its own cap;
- Any growth in demand for water for significant new industry and for future Commonwealth use will be provided for through water trading; and
- Existing cap credits (water from our cap we did not use in previous years) will be recognised. The ACT already has a cap credit of in excess of 60 GL. So if we use more than our cap in a year, we can use our credits to offset that extra use.
The ACT's water cap will be reviewed after 2011, as part of the new Murray Darling Basin administrative arrangements.
Note that water provided to Queanbeyan by the ACT and water Queanbeyan returns to the rivers is included in the ACT cap.