Proposed Basin Plan consultation report
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- Groundwater Sustainable Diversion Limits
Shared reductions27.Issue The ‘shared reduction’ component of the SDLs attracted strong commentary relating to lack of certainty and equity. Submissions sought an apportionment of this component. ‘The uncertainty bough about by the 971GL/year shared reduction target makes it impossible to accurately estimate the impacts.’ Submissions also expressed concern about the volume of shared reductions that regions might have to contribute; others questioned why a certain connected valley was included or excluded among those required to contribute to shared reductions. Other submissions agreed with the proposed market model for recovering shared reductions. ‘[Submitter’s name] is an advocate of a cost-effective, market-based approach to meeting environmental water requirements (where these are scientifically based), and as such, is not uncomfortable with the concept of a shared reduction.’ RESPONSE The ‘shared reduction’ approach was taken to provide greater flexibility in where environmental water can be recovered, to enable recovery at the least economic cost and to allow market forces to operate. This approach also allows governments undertaking water recovery to consider both how environmental water needs are best met and system constraints that could limit where water can be recovered to meet these needs. MDBA’s view is that the benefits of this flexibility outweigh the disadvantages of certainty about where the reductions will occur. Further, transparency of the Australian Government’s water recovery, through the publishing of a water recovery strategy, will assist in addressing uncertainty. Each upstream catchment must meet its own environmental watering needs, but the system’s major trunk rivers, the Barwon-Darling and the Murray, rely on significant inflows from their tributaries to complement some local inflows directly into the trunk rivers. Some of the additional reductions required to meet the environmental needs in these two catchments will need to be sourced from upstream catchments. MDBA has not specified how much water each catchment must contribute to the shared reduction amounts, other than to acknowledge that some catchments are physically restricted from reliably contributing to downstream flows because they are only tenuously connected to the system’s major waterways. The 2015 SDL review will be an opportunity to review whether the shared reduction can be distributed. At that time there will be more information available on the location of works and measures that may affect the SDLs and progress on recovering water particularly through infrastructure investments, as well as where best to recover water to meet the range of environmental water needs. Groundwater Sustainable Diversion Limits28.Issue Submissions were critical of the changes to groundwater SDLs in the proposed Basin Plan compared to baseline diversions and diversions proposed in the Guide to the proposed Basin Plan (the Guide). Some submissions focused on the magnitude of change in total SDLs between the Guide and the proposed Basin Plan. The feedback focused on two main areas: concern that the change in the groundwater SDLS would have an impact on the surface-water resources of the Basin; and that the groundwater SDLs were set too high and that they represented an unsustainable level of take. ‘Much greater scientific understanding of the relevant groundwater resources and the degree of connectivity between surface and groundwater systems in the Basin is required...it is at best premature to be suggesting such huge increases in groundwater extraction when so little is known about the long-term consequences of doing so.’ The submissions in general looked at the aggregated volume of the SDLs across the Basin and were concerned that the increased groundwater SDLs compared to the Guide would largely negate the gains from reducing surface-water take across the Basin. Implicit in some of the submissions was the assumption that the groundwater resources of the Basin could be aggregated to a single volume and for every 1 ML of groundwater extracted there was a corresponding 1 ML reduction in surface water flow due to the connectivity between surface and groundwater. Some submissions stated that they do not believe that there was enough information and science to set the unassigned groundwater SDLs at the levels in the proposed Basin Plan. They believed MDBA should take a more conservative approach and reduce the unassigned groundwater SDLs. These submissions said that further increases in the groundwater SDLs should occur only when additional information and science were available to determine the groundwater SDLs more accurately. ‘[Submitter’s name] questions whether there is sufficient evidence to indicate that the proposed SDLs represent an ESLT for groundwater.’ There were also some that considered the groundwater SDLs to be too conservative and that they should be higher. Some of these submissions suggested that uncertainty factors that had been applied were not appropriate and should be removed to allow a higher level of groundwater take. RESPONSE Submissions raised significant concerns about the groundwater SDLs in the proposed Basin Plan. In response to these issues MDBA undertook further analysis and consulted with groundwater experts and has decided to change some elements relating to groundwater SDLs in the proposed Basin Plan. In summary the result is a reduction in the overall groundwater SDL from 4340 GL/y to 3,184 GL/y. The response below sets out the changes made and the basis for these changes. Recap on the groundwater provisions in the proposed Basin Plan In the period between the release of the Guide to the Basin Plan and the release of the proposed Basin Plan, changes to the assessments of the groundwater Baseline Diversion Limits (BDLs) and SDLs resulted in a change in the total of groundwater BDL was 1,787 GL/y to 2,352 GL/y, and for SDLs from 2,095 GL/y to 4,340 GL/y. Two reports published by MDBA provide details of the groundwater settings in the proposed Basin Plan and the methods applied in this work:
Revisions to groundwater provisions arising from consultation and further work In response to concerns raised during the consultation period and through submissions received on the proposed Basin Plan regarding the groundwater SDLs, MDBA carried out further investigations on particular matters associated with groundwater provisions. This work included issues raised in individual submissions and also the convening of a review workshop of groundwater professionals to review the MDBA groundwater methodology and discuss the applicability of the methods used to determine the proposed groundwater SDLs. In response to the further work on the groundwater provisions, MDBA revised a number of the groundwater SDLs. As a result the total of groundwater SDLs in the proposed Basin Plan is now 3,184 GL/y. Changes to groundwater SDLs Revision of unassigned water availability The largest change in the proposed SDLs in the proposed Basin Plan is in the areas with unassigned water. The total change is a reduction of around 1,000 GL/y distributed across 35 groundwater SDL areas. Unassigned groundwater is the groundwater that can be made available for consumptive use above the BDL. In the proposed Basin Plan released for consultation, for groundwater systems where a technical assessment identified the potential for unassigned water, depending on the system, half or all of the increase up to the limit indicated by the technical assessment was allowed (i.e. an unassigned water factor of 0.5 or 1.0 was applied). After further investigation and consideration by a group of experts, a number of options were explored focusing on modification of the unassigned groundwater factors, and the implications arising. The characteristics of each of the three broad aquifer systems were considered and key arguments for revision identified:
In response to this further work, including the key arguments set out above, a consistent and more precautionary approach to unassigned groundwater was adopted by MDBA for the proposed Basin Plan. In summary, an unassigned groundwater factor of 0.25 is now applied throughout areas with unassigned groundwater. Revision of groundwater SDL in the Gunnedah-Oxley Basin A change has also been made to the SDL for the deep groundwater resources of the Gunnedah-Oxley Basin. The SDL has been reduced from 300 GL/ to 102 GL/y. The initial proposal was based upon the forthcoming NSW plan limit, adjusted to accommodate the way MDBA specified limits on groundwater extraction nearer the land surface. The revised proposal is based upon the method adopted in other such systems in the Basin, coupled with the revised unassigned water assessment approach set out above. This approach will allow future incorporation of the additional information on this aquifer that will become available through the Namoi Water Study and projects funded under the Independent Expert Scientific Committee on Coal Seam Gas and Coal Mining. Other changes incorporated Changes to the SDL areas and associated SDLs have occurred in Victoria. Victoria now has two SDL areas for the part of the state within the Basin. A change has also occurred in the Victorian Goulburn-Murray: Sedimentary Plain area (GS8) where the SDL has increased by 42 GL/y after a review of the numerical groundwater model, where a peer review had identified the earlier interpretations of results as unduly conservative. On review, MDBA decided to adjust its approach in this case. In NSW, MBDA has merged two Water Resource Plan areas into one (New South Wales Great Artesian Basin Shallow) with three SDL areas rather than the two in the proposed Basin Plan. NSW has also provided updated information regarding entitlement and stock and domestic use used to determine the groundwater BDLs. There have been small increases and decreases in a number of NSW SDL areas.
Some submissions expressed a view that there was a technical argument for making further reductions in the NSW areas which are currently undergoing a reduction program. MDBA previously agreed to allow the reduction program to be completed before any further revisions were considered. Given that any change would be in the context of compounding uncertainty in the systems as current reduction programs have not been completed, and noting that storage volume in these systems exceeds 200 years of use, MDBA considered these views but decided to maintain the SDLs in the seven SDL areas in New South Wales currently undergoing a reduction program. Further documentation Some submissions on the proposed Basin Plan groundwater provisions expressed a desire for more detailed technical information to inform the provisions of the Basin Plan itself. MDBA is committed to providing the supporting documentation associated with its proposal. This includes the recent changes to groundwater SDLs in the proposed Basin Plan. Accordingly, addendums to the proposed Groundwater Baseline and Sustainable Diversion Limits: methods report8 and the Groundwater Sustainable Diversion Limit Resource Unit Summary Report Cards9 will be released in June 2012 to further document the changes that have been made. MDBA considers that the groundwater SDLs set out a sustainable framework for the management of groundwater in the Basin. 29.Issue
Groundwater data availability is variable across the Basin. There are areas with metering and high levels of groundwater monitoring and associated information, and other areas without metering and low levels of groundwater monitoring and other information. Where data and numerical groundwater models were available, numerical modelling was carried out in 13 SDL resource units which account for about 80% of groundwater use in the Basin. Where numerical models were not available, MDBA used a recharge risk assessment method (RRAM), originally developed for CSIRO. In determining the groundwater SDLs, the numerical groundwater models and RRAM considered the risks of groundwater extraction on:
Information on the methods used to develop the SDLs is available in two key reports setting out the methods and the technical information and data used during the development of the individual groundwater SDLs for the proposed Basin Plan:
There have been a number of revisions to the SDLs in schedule 4 of the proposed Basin Plan: Matters relating to groundwater SDL resource units. These changes are described in the response to issue No. 28 30.Issue Submitters were critical of the exclusion of the water resources of the Great Artesian Basin from the proposed Basin Plan. RESPONSE Section 4 of the Act defines Basin water resources as excluding groundwater that forms part of the Great Artesian Basin. Consistent with this, the Great Artesian Basin has been excluded from the provisions of the proposed Basin Plan. Yüklə 0,77 Mb. Dostları ilə paylaş:
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