In order to manage the entire water resource in the Murray-Darling
Basin, the Basin Plan also sets Sustainable Diversion Limits (SDLs) and
Baseline Diversion Limits (BDLs) for groundwater. The groundwater SDLs and BDLs
have been developed in a manner similar to surface water SDLs and BDLs as
discussed in the previous chapter. The definition of the SDL and BDL apply to groundwater
in the same way as to surface water (see chapter two).
This chapter discusses how the Murray-Darling Basin Authority (MDBA) has
set groundwater SDLs and BDLs and how they have changed significantly over the
various iterations of the Basin Plan. It also discusses the key criticisms of
the modelling of groundwater for the Basin Plan. Finally the chapter details
the concerns with the treatment of the connectivity of surface water and groundwater
resources in the Basin Plan.
Groundwater SDLs and BDLs
In the final version of the Basin Plan, the MDBA set the Basin-wide SDL
for groundwater at 3334 GL/y. The BDL for groundwater is set at 2386 GL/y.
The SDLs and BDLs for groundwater proposed by the MDBA have varied
significantly across the different versions of the Basin Plan. Table 3.1 lists the
groundwater SDLs and BDLs from the MDBA's Guide to the Proposed Basin Plan (the
Guide) through to the final Basin Plan.
As Table 3.1 indicates, the Guide provided for a relatively small increase
(309 GL/y) between the total Basin SDL (2095 GL/y) than the total Basin BDL
(1786 GL/y). The total allowable extraction of groundwater increased greatly
under Basin Plan (November 2011) with a SDL/BDL difference of 1988 GL/y. Under
the final Basin Plan this SDL/BDL difference was reduced to an increase of
948 GL/y but still represents a much larger increase in ground water
extraction than proposed in the Guide.
SDLs and BDLs from the Guide to the Basin Plan
Plan (November 2011)
Plan (May 2012)
Plan (August 2012)
Basin Plan (November 2012)
Unlike surface water which had extractions limited by the 1995 cap
agreed to by Basin states, no equivalent constraint has been applied to groundwater
use. As a result, the MDBA developed the BDLs for the Basin in reference to current
groundwater extraction levels and water entitlements. The Basin Plan divides
the Basin up into 66 groundwater SDL resource units (based on state planning
boundaries and hydrogeological regions) and sets a BDL and a SDL for each.
The number of SDL resource units has change across the various iterations of
the Basin Plan – for example, there were 79 resource units in the May 2012
version, and 70 SDL resource units in the August 2012 version.
The Basin-wide groundwater BDL and SDL is the sum of individual BDLs and SDLs across
all the groundwater resource units, respectively.
Determination of groundwater baseline diversion
As a reference point, the MDBA determined the BDL for each SDL resource
unit on the following basis:
1. where a water management plan or proposed plan exists, the
BDL is the plan limit unless the plan limit is greater than the level of
entitlement, in which case the BDL is the entitlement;
2. where there is no plan, the BDL is the entitlement along
with the effect of any rules managing extraction; and
3. where there is a cross-border agreement for groundwater
management, the extraction limit under the agreement is the BDL.
The MDBA has indicated that this policy is the most 'accurate reflection
of the limits of use imposed on current groundwater planning arrangements.'
The Basin states provided the MDBA with estimates of average use of groundwater
resources for the period 2003-04 to 2007-08. The MDBA stated that 'small
changes to some BDL estimates' had to be made following receipt of this
Modelling for groundwater sustainable diversion
According the MDBA, the proposed groundwater SDLs were informed by
numerical groundwater models or an analytical risk assessment which provided
the 'potential volume of water available for consumptive use' or the
preliminary extraction limit (PEL).
The MDBA undertook numerical modelling for 13 of the 79 groundwater resource
units where numerical models were already available. The MDBA also needed to
supplement this analysis with a Recharge Risk Assessment Method (RRAM) for the
remaining 66 groundwater resources units, as numerical models were not
available in all areas. The MDBA explained this approach:
Numerical modelling was carried out in 13 SDL resource units
where there were fit for purpose numerical models available. Where numerical
models were not available the [MDBA] has used a recharge risk assessment method
(RRAM), developed for the MDBA (CSIRO and SKM 2010), to inform the proposed
SDLs. Both the numerical groundwater modelling and the RRAM
provide the potential volume of water available for consumptive use.
The MDBA stated that the numerical models used 'represented systems that
covered 73% of the groundwater [extracted] in the Murray-Darling Basin in
The MDBA explained that for the development of SDLs for resource units
where numerical model were not available (i.e. through RRAM) that:
...the first step in determining the PEL using RRAM was to
determine recharge across the Basin using the Water Vegetation Energy and
Solute (WAVES) model and upscaling techniques developed for the Murray‑Darling
Basin Sustainable Yields project and subsequently refined for the Basin Plan
(Zhang and Dawes 1998 and CSIRO 2010). Additional recharge information was also
used where it was made available by the states.
Modelling of groundwater SDLs included the MDBA developing a 'groundwater
assessment framework' which involved two stages:
The first stage considered the characteristics of the
individual groundwater resource units. Each groundwater SDL unit was
characterised as either:
- Deep groundwater;
- Non-renewable groundwater;
- Connected groundwater; or
- Non-connected groundwater.
The second stage assessed the Authority’s determination of
the BDL and assessment of the PEL in conjunction with the current or proposed groundwater
management arrangements to determine the SDL for each groundwater SDL resource
unit. The assessments within each of the characterisation groups considered:
is there an existing reduction program in place;
- is the BDL greater than the PEL;
is the BDL equal to the PEL;
is the BDL less than the PEL; and
- is there more up to date science or knowledge, or existing or proposed
water management arrangements in place and how do they relate to the BDL and
Addendum Report on Groundwater modelling
In July 2012, the MDBA released the Addendum to the proposed Groundwater
Baseline and Sustainable Diversion Limits: Methods Report (Addendum).
This report provides updated information regarding the modelling for
groundwater BDLs and SDLs. This included a review of the groundwater
assessments by the MDBA and other groundwater experts and led to a decrease in
the Basin-wide groundwater SDL from 4340 to 3184 GL/y in Basin Plan (May 2012).
The review included:
- an explanation of how the potential impacts of groundwater take on
surface water were accounted for when setting the groundwater SDLs;
- a discussion on data quality and how it was considered in the review;
- changes to deep groundwater SDL resource units.
The MDBA acknowledged there was limited science available for setting
groundwater SDLs and stated a 'conservative approach' should be adopted. According
to the MDBA, this approach provided the justification for some SDLs
being reduced in the Basin Plan from the initial estimates that were outlined
in the Guide.
This is despite the significant overall increase in the Basin-wide SDL
from the Guide to the first iteration of the Basin Plan.
The MDBA reassessed the information and data used to inform the SDLs in
the Basin Plan (November 2011) and determined that the most appropriate method
of revising the groundwater SDLs was to alter the 'unassigned groundwater assessment'
in three broad groundwater systems, the: Lachlan Ford Belt System; Highland
System; and the Western System. The revisions in these groundwater SDLs
focussed mainly on unassigned groundwater and deep aquifers. Unassigned
groundwater is the groundwater that can be 'made available for consumptive use
above the BDL'.
The MDBA's major reports that publicly detail groundwater SDLs, BDLs,
and SDL resource units pre-date some changes to the groundwater SDLs, BDLs and
SDL resource units that are listed in the final Basin Plan. Some of the
evidence discussed below refers to SDL, BDL and SDL resource unit figures from
earlier versions of the plan and therefore may differ from the figures included
in the final Basin Plan. However, despite the changes in numerical values, the
committee considers that the general thrust of the criticisms raised below have
not been altered by the final version of the Basin Plan.
Key criticisms of groundwater modelling
In April 2012, the Wentworth Group of Concerned Scientists (Wentworth
Group) stated in its analysis of the groundwater in Basin Plan (November 2011)
that the BDLs have 'changed considerably' since the Guide (from 1786 to 2352
GL/y) and that no evidence had been provided to justify these increases:
Across the Basin as a whole there have been some baselines
that have increased and some that have decreased.
However the accumulated decrease in baselines across the
Basin is less than 20 Gl. On the other hand, the accumulated increase in
baselines across the Basin is in excess of 600 Gl. This dramatic increase in
claimed baseline water use matters. Since the Baseline Diversion Limit is used
to establish the Sustainable Diversion Limit this large creep in baseline use
in just 13 months has the effect of increasing the Sustainable Diversion Limits
available for consumptive use and decreasing the available environmental water.
The Murray-Darling Basin Authority provides no evidence to
justify the 600 Gl increase in baselines over the 13 month period since the
publication of the Guide.
The Wentworth Group claimed there was no new modelling undertaken since
the Guide and which would explain the groundwater SDLs as per the Basin Plan
In the 12 months since then, there has not been any new
science done—let us make that clear—but there has been a change of 2,600
gigalitres. We have increased the amount of groundwater we can take by 2,600
gigalitres. I am a little bit shocked at that without new science to back that
The RRAM approach was criticised by stakeholders for the lack of
scientific review. Environment Victoria's Healthy Rivers Campaigner, Ms Juliet Le
Feuvre explained this criticism stating the groundwater SDLs:
[are] based on the recharge risk assessment model, which
estimates on a very broad basis what recharge to groundwater is. They [the
MDBA] say that they have taken a precautionary approach and halved it and
halved it again, but there is no scientific review of the model that they have
used, so it would not be a precautionary approach at all.
The Wentworth Group also challenged the validity of the modelling
undertaken for groundwater SDLs stating there were key limitations and flawed
assumptions made with this approach:
The draft Basin Plan divides the Murray-Darling Basin
aquifers up into
79 groundwater units [Basin Plan (November 2011)]. Numerical groundwater models
currently cover 13 of these 79 resource units. The areas covered by the models
are generally the most heavily used alluvial systems...
The Recharge Risk Assessment Method was used as a
prioritisation tool for the Guide to the Basin Plan. Its results were never
intended to be used to provide quantitative recharge estimates...
Given the great uncertainties in the calculation of the
recharge rates, the need to retain groundwater resources for future
generations, and the limited information available about reliance of ecosystems
on groundwater discharges, using risk factors of 50% and 70% of the recharge is
Given the information gaps regarding groundwater in the Basin, many
stakeholders have argued for a precautionary approach to be taken. For example,
the National Water Commission (NWC) has stated that the potential impacts
regarding extraction of water from groundwater systems will take a long time to
emerge so an adaptive and precautionary approach is essential.
The Basin State Ministers also supported a precautionary approach for
all aquifers consistent with the NWC position and also noted that extraction
limits for groundwater resources may shift over time depending on new
information and the best available science in relation to these resources.
Despite the prospect for future review some stakeholders claimed the
proposed amount of extraction is too high. For instance Dr Paul Sinclair from
the Australian Conservation Foundation stated:
The increase in groundwater extraction contemplated by the
proposed basin plan is reckless. The draft plan proposes to increase the
extraction of groundwater by 2600 gigalitres, about the same amount it once
returned to the rivers. Enormous amounts of public money and effort are being
dedicated to addressing the problems that have arisen from past decisions to
over-allocate surface water based on poor understanding and political self‑interest.
The authority should be prevented from repeating the mistakes of the past.
The Wentworth Group was also critical of the modifications made to
groundwater extractions after Basin Plan (November 2011), arguing that the Basin‑wide
groundwater SDL in subsequent version of the Basin Plan were not based on
strong scientific evidence. As Mr Tim Stubbs explained:
We have had a pretty comprehensive look at that huge increase
[in Groundwater Methods Report] and we released a submission asking a lot of
questions about the science justifying that increase. We could not see that
science. The authority put out a subsequent document [Addendum] but again it
really lacked the details and proved to have some very dubious assumptions in
it—assumptions that were made to get to those final numbers. It was very
interesting that a number of weeks after that version a subsequent version of
the plan [Basin Plan (August 2012)] came out and we saw a drop of around 1,000
gigalitres in those groundwater numbers. Craig Knowles said at a media
conference, I think, that he got the boffins in a room and looked at the
numbers. That translated to a one-day workshop with a handful of groundwater
experts and others. The big concern is that we are making decisions about the
future of the Murray-Darling basin through a one-day workshop. It is an
interesting way of going about public policy, particularly when we are spending
huge amounts of money and time modelling the surface water and saying how much
water needs to go back in there, and then completely separately having a
one-day workshop to adjust the volumes of groundwater by around 1,000
gigalitres. And the two are connected.
Connectivity between surface and groundwater
resources in the modelling
Groundwater and surface water connectivity was perhaps the single most
contentious issue regarding the treatment of groundwater in the Basin Plan.
The committee heard extensive evidence that the two resources should be treated
as closely linked and that Basin Plan did not adequately address this issue.
The National Water Commission has stated that although it is not always
apparent, these resources are 'intimately linked' and should be managed as a
single resource, unless proven otherwise.
Conservation Councils in particular have stated that the water resources
in the Basin need to be considered as connected when considering how much groundwater
is sustainable to extract. For example Mr Tim Kelly, Chief Executive of the
Conservation Council of South Australia stated that 'by default, these systems
should be treated as connected' and that the MDBA 'should not be allocating
further water from them.'
This position was echoed by the Wentworth Group that stated the Basin
Plan's failure to include the impact of increasing groundwater extractions in
the surface water modelling means the surface water SDLs are unlikely to
deliver the claimed outcomes. The Wentworth Group analysis of the Basin Plan
(November 2011) stated:
The failure to adequately analyse the impacts of increasing groundwater
extractions on surface water means the draft basin Plan will not adequately
protect environmental assets, particularly those dependent on low flows.
Dr Bill Young from the CSIRO advised the committee that, as with the
surface water SDLs, the adaptive management approach that the MDBA have stated
it will use will allow for further consideration of new science and information
in relation to groundwater and surface water connectivity:
The surface water impacts from the groundwater...will take a
long time to emerge. There is a review process that has been put in place.
There may be no demand for that increase in groundwater use to happen in a
hurry, but that does not necessarily mean it is scientifically defensible. But
it does not mean it is necessarily risky either. There is an opportunity to
review this. If the authority follows through with its commitment to adaptive
management, we will be monitoring the increases in use, we will be monitoring
the impacts on stream flows and we will be monitoring the consequences and
outcomes for environments across the basin.
The CSIRO was also critical about the level of rigor that MDBA applied
to this issue:
...the evidence base that has been presented by the authority
to date to support the [Basin Plan (November 2011)] has not demonstrated that
it has undertaken a rigorous assessment of the surface water impacts of the
proposed levels of groundwater take.
Other Basin stakeholders also voiced concerns regarding the limited
knowledge and scientific understanding of the impact of the proposed groundwater
extractions. Professor Mike Young noted that he did not believe the appropriate
amount of information was available for the approach the MDBA was taking with groundwater
under the Basin Plan (November 2011) and that he supported the NWC approach to
Another witness, Ms Beverly Smiles from the Inland Rivers Network explained:
One of the concerns is that where this new groundwater
extraction is being proposed overlays the Great Artesian Basin in recharge
areas, and there is a whole range of concerns around this proposal. Those of us
who have been following water for a long time know that the knowledge and
science around groundwater is relatively new compared to what we know about
what is in front of our faces on a regular basis with surface flow.
Some stakeholders have suggested any increases to groundwater extraction
should be delayed until detailed evaluations are completed:
Any consideration of increased extraction should be delayed
until a thorough assessment of characteristics, surface groundwater
connectivity, groundwater dependent ecosystems and resource sustainability can
be carried out.
The Wentworth Group have strongly criticised the assumptions used to
calculate the diversion limits and have stated the assumptions used 'ignore the
long‑term connectivity of surface and groundwater' resources:
...in documentation supporting the draft Basin Plan [November
2011] the [MDBA] states that for the purpose of determining Sustainable
Diversion Limits, rivers that are classified as losing streams (i.e. ones where
there is a flux of water from the rivers to the underlying aquifers) can be
treated as unconnected systems. This is then used to justify the assumption
that drawing these aquifers down further will not increase the loss of water
from the overlying rivers.
However, this assumption is incorrect. The aquifers that
receive water from losing river reaches will provide water to these rivers
further upstream or downstream; i.e. there are gaining reaches elsewhere.
Allowing additional extractions from these aquifers simply means that the level
of the watertable will drop, and the extent of the losing stream will increase
into areas that are currently gaining streams. Reducing the length of these
gaining streams will affect river flows, including important base flows.
Dr John Williams summarised the Wentworth Group's concerns about the Basin
Plan (November 2011) introducing uncertainty by not considering the water
resources as connected:
...we need to realise that groundwater and surface waters are
connected, in most instances. At the moment, until you establish where the groundwater
systems are and without recognising the implications of taking water out of the
groundwater system on the surface water—and that being done properly, which the
Basin Plan does not do—you have no understanding of the impact of the groundwater
allocations on the subsequent surface water allocations, which makes them most
The issue of groundwater connectivity remained a key concern of the Wentworth
Group as the final Basin Plan was presented to Parliament in November 2012. On
this basis, one representative of the Wentworth Group raised doubts about the
reliability of the 3200 GL/y relaxed constraints surface water modelling:
We accept that the 3,200 modelling, with the eight
constraints removed, would produce a substantive improvement in the health of
the river system, subject to two significant and important caveats. The first
is: that would require an assumption that increases in groundwater extraction
would not have a negative impact on stream flow, which is an enormous
assumption that we do not believe is valid...
This was detailed further by the Wentworth Group as the following
Mr Cosier:...the plan proposes an increase in surface
water flow of
2,750 gigalitres. It also proposes an increase in extraction of groundwater by
1,700 gigalitres. The modelling for the environmental outcomes for both the
2,750 gigalitres and the 3,200 gigalitres with the constraints removed assumes
that groundwater will have no impact on streamflow.
Senator NASH: Assuming there is no connectivity.
Mr Cosier: Assuming there is no connectivity. The
National Water Commission advice to government is the absolute opposite. If you
cannot demonstrate no connectivity, you should assume 100 per cent
connectivity. As it stands, we are looking at a scenario of 2,750 gigalitres
being added to the river [through increased surface water flows] and
1,700 gigalitres being taken from the river [through increased groundwater
As a result of the MDBA's treatment of ground‑surface water
connectivity, the Wentworth Group claimed the environmental outcomes achieved
by the 2750 GL/y reduced surface water extractions could not be properly
evaluated because of the lack of information about the impacts of increased groundwater
extractions. As Mr Cosier and Mr Stubbs explained:
Mr Cosier: ...The plan as it has been presented to
parliament is for a
2,750 gigalitre SDL target. The public documentation we have from the [MDBA] is
that that will achieve a certain number of environmental outcomes based on 113
indicators that have been referred to recently. All of those comments, all of
those statements...ignores groundwater extraction. So parliament is being
presented with a basin plan that pretends to produce certain environmental
outcomes for the volumes that parliament believes it is being asked to sign up
to, when in fact none of those outcome targets have incorporated anything to do
with groundwater extraction.
Senator XENOPHON: And that is the question you think
ought to be put to the [MDBA]...?
Mr Cosier: Yes. And, our view is that, if it is not
satisfactorily answered by the [MDBA]...the parliament should reject this plan.
Mr Stubbs: I think the question to be asked is: can
the [MDBA] quantify the volumetric impact of that groundwater extraction on the
river system? If the [MDBA] cannot provide you with a number which you can then
subtract from the 2,750 to understand what volume will actually be flowing down
the river and then go and look at the outcome targets or rerun the model to
find out what that volume will actually achieve—if the [MDBA] cannot reply to
you with a number—then clearly you cannot understand what we are actually
getting, because you can never subtract that number from the 2,750 and you can
never rerun the model to find out whatever that number is and what
environmental outcomes you will actually be signing up to. Until you can do that,
you do not know what you are signing up to as far as environmental outcomes.
The Australian Conservation Foundation also noted the new modelling for
3200 GL/y did not take into account any future impacts from additional
The MDBA responded to this issue and challenged the groundwater
extraction figures used by the Wentworth Group:
The [MDBA] strongly refutes the statements by Mr Cosier at
the public hearing on 23 November 2012 that the Basin Plan “proposes an
increase in extraction of groundwater by 1,700 gigalitres” and “potentially
1,700 gigalitres being taken from the river”. The Basin Plan sets the Basin
wide groundwater baseline diversion limit (BDL) at 2,386 GL/y, which reflects a
more accurate determination of the potential extraction under current planning
arrangements than the estimate of the BDL as at late 2010 which appears to
inform Mr Cosier’s remarks. The Basin wide groundwater SDL of 3,334 GL/y
allows for an additional 984 GL/y of overall groundwater use above the
The MDBA also challenged the idea of assuming 100 per cent connectivity
of surface and groundwater resources. As Dr Rhondda Dickson told the committee:
...The Wentworth Group have characterised groundwater as if
it were one whole combined pool that was all directly linked to surface water.
That is very simplistic and wrong—that is not how the system works...
There are 66 different aquifers that have been assessed... [F]or
most of the aquifers that are highly connected to surface water—a lot of the
alluvial aquifers—there is no increase in the diversion limit. The baseline
diversion limit is determined and then the sustainable diversion limit is the
same as that—there are a couple where it is a little bit lower; there is one up
There are a lot of other aquifers that have very little
connection, or no connection in the case of some fossil aquifers, with surface
water, so there are different issues to consider. The issue of recharge is a
key consideration in determining the sustainable limits of those. The
simplistic point that is being made is just not correct and does not have any
grounding in science. It is just a simplistic expression of how the system
The MDBA further stated that:
As part of the determination of groundwater SDLs the [MDBA]
has categorized the level of connectivity between surface and groundwater
resources as high, medium or low. There are 30 of 66 groundwater SDL areas
where the connectivity level has been classified as low.
The MDBA also explained:
In relation to the potential impact on surface water of the
increase in groundwater use permitted under the Basin Plan, the Authority’s
July 2012 Addendum to Groundwater Methods Report (p10) relevantly states:
“In regards to the issue of the potential impact of
groundwater extraction on surface water resources the MDBA has calculated that
the unassigned groundwater assessment for the revised draft Basin Plan (28 May
2012) has a potential reduction in surface water resources from unassigned
groundwater extraction in the Lachlan Fold Belt and Highland unassigned systems
of between 29 and 58 GL/y. It is essential to note the time span of the
potential impacts can vary from a few years to hundreds of years and in some
cases may never be realised. Mindful of this context, the MDBA is of the view
that this is an acceptable risk”.
The groundwater SDL revisions since May 2012 do not change
the scale of the Authority’s assessment undertaken for the revised draft Basin
The committee considered the issue of surface-groundwater connectivity
in its interim reports for this inquiry and is disappointed that this issue continues
to be only partially addressed by the MDBA through separate groundwater
modelling. The committee supports the Wentworth Group's statement that the Basin
Plan fails to fully assess the impacts of increasing groundwater extraction in
the surface water modelling which undermines the effectiveness of the MDBA's
SDLs to deliver a healthy basin.
The committee also supports the recommendation of the Windsor report
which states that 'the Murray Darling Basin Authority improve data of groundwater
availability, use and connectivity with surface water prior to proposing
sustainable diversion limits for groundwater.'
The committee notes with concern that the MDBA has not done more to address this
The MDBA has acknowledged that groundwater SDLs may be adjusted
according to new information presented through current research projects.
The committee welcomes and acknowledges that the MDBA has taken steps to
improve groundwater information. While it is accepted that certain groundwater
information will take time to develop and that SDLs should be adapted
accordingly, the MDBA needs to make the rationale for future changes as clear
as possible to the public and the Parliament.
The committee supports the suggestion by the workshop of groundwater experts
for an ongoing Groundwater Advisory Group
to provide technical advice to the MDBA on groundwater matters. The committee strongly
encourages that any such group include experts in relevant fields, such as
climate change and coal seam gas mining to inform changes to groundwater SDLs.
The committee considers that formal and public updates from such a group would
help Basin stakeholders and communities further understand groundwater issues
and improve the public accountability of the MDBA regarding this issue.
The committee recommends that before 2016 the MDBA undertake a thorough
review of the groundwater aspects of the Basin Plan including:
- the methodology and the assumptions underpinning the groundwater
BDLs and SDLs; and
- the connectivity of all groundwater and surface water resources
to ensure that the modelling used in the Basin Plan is scientifically sound.
The committee also recommends that in conducting this review the MDBA
should consult with a range of scientific experts. To ensure reliability, the
final review findings should be peer reviewed by the CSIRO. To ensure
transparency, the results of the review should be published by the MDBA.
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