Revision of sustainable allocation is needed
The revised Plan will take a different approach to sustainable allocation in comparison to the current Plan. The amendment process will explore acceptable impact and use groundwater models to inform sustainable allocation.
When water is taken from the groundwater system it has an impact. The scale, timeframe and values impacted will vary. Acceptable impact is based on understanding what impact from consumptive uses we accept. It will consider all values including economic, environmental, social and cultural.
The amendment process is now starting to look at acceptable impact.
Have you experienced any of these impacts:
Have you had to deepen a stock and domestic bore in the last 5 years?
Have you noticed a change in your water quality over the last 10 years?
Have you noticed a change in the yield from a bore over the last 10 years?
The Plan sought to manage groundwater sustainably by setting a target management level for each management area of the confined and unconfined aquifers. This is evidence that the sustainable limits cannot manage the resource for continued social, economic, cultural and environmental benefit of current and future generations.
In the unconfined aquifer the target management level is based on a proportion of recharge in the management area. The allocation of a proportion of recharge is an equitable and logical approach. Particularly as at the time of developing the Plan a regional groundwater model was not available to test use scenarios. But the proportion of recharge allocated for use was not a precautionary approach and lacked consistency with the objectives of the Plan. The allocation of 90% of mean annual vertical recharge is a very high proportion. It relies on an accurate estimate of recharge, allowing no room for error. The recharge values for the Plan were determined from a variety of available sources, some dated to 1978 and 1995. Allocation of 90% of mean annual vertical recharge failed to consider that recharge was known to have declined since those values were determined. In low and moderate risk management areas the Plan allowed for greater than 90% of recharge to be allocated where allocations exceeded the sustainable limit. Allowing for over-allocation in any management area is contradictory to managing risk to the resource.
Some groundwater declines that the Plan identified in the lead up to adoption have continued. Water use is approximately 50% of allocation in the confined and unconfined aquifers. If water use increases in combination with a changing climate, groundwater level declines will continue.
