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Published: 02 May 2012   •   Speeches and transcripts

Over the past months there have been criticisms that the draft Murray-Darling Basin Plan does not take climate change into account. In a speech to the 'Practical Responses to Climate Change' conference Rhondda Dickson, Chief Executive, Murray Darling Basin Authority explains why this is not the case.

The Murray-Darling Basin Plan: Adaptive management in a changing climate

Dr Rhondda Dickson, Chief Executive, MDBA

Today I'm talking about managing water resources in the Murray-Darling Basin, and how climate variability and climate change are factored into the Murray-Darling Basin Plan.

The Basin is huge. It covers a million square kilometres across 4 states and the ACT, and crosses several different climate zones.  All these zones have highly seasonal climate patterns as well as huge variability between years that produce the extreme floods and droughts like those we've experienced over the past decade.

A conundrum that climate scientists are fond of pointing out is how to distinguish the signals of long-term climate change from the natural variability - or noise - in a system.  This is no more evident than in the Murray-Darling Basin.

Leaving aside the challenges of climate science uncertainty for a moment, I would like to turn to what we can be certain about.  There is more than enough information to be confident about the two key challenges in managing the water resources of the Basin:

The first – is over-allocation.  At some point, after the middle of last century, we, the collective governments, began to over allocate the water resource.  The early signals were rising salinity levels during the 1970s, the closing of the Murray Mouth in 1981, the massive blue-green algae blooms in the Darling River in the early 1990s, all well before the significant environmental deterioration we saw in the recent Millennium drought.

The second - the highly variable climate of the Murray-Darling Basin will continue in the future. The big droughts and floods will come again and it's likely that these extreme events will become more frequent and intense in the future.   And the science is telling us that the most likely trend is for a drying climate, particularly in the southern Basin.

The draft Basin Plan addresses these two key challenges.

Addressing over-allocation by establishing sustainable limits to water extraction and returning water to the environment to restore the health of the system. 

This will increase the long-term resilience of the system and will allow the rivers, wetlands and floodplains to cope better in future drought years and to be in a much better state to adapt to a changing climate.

Managing for future climate by establishing an adaptive management framework and new ‘whole-of-basin' arrangements that allow flexible responses to new information about our changing climate system. 

Water management in the Murray-Darling Basin will always be a hostage to climate.  An adaptive management approach is the only way in which we can manage for an uncertain future.  An approach that allows for better understanding of future risks, incorporates new knowledge, allow opportunities for innovation, and draws on the ideas and local knowledge of people all across the basin.

How the Basin Plan deals with climate variability

In setting limits on take, you first need to start with the objectives you are seeking.

The MDBA's vision is for a healthy, working Murray–Darling Basin that supports strong and vibrant communities, resilient industries and a healthy environment.

The aim then is to address over-allocation – in a way that optimises environmental, economic and social objectives.  

The Basin Plan is about redistributing some of the water currently diverted for agricultural, industry and town use back into the environment.   This environmental water will be used to return many of the small and medium periodic flood events that have been missing from the system for decades.  And will greatly improve the connection of the river to its floodplains and thus the overall health of the system.

Under the Basin Plan, the Authority is proposing that 2750 gigalitres of environmental water be recovered from a 2009 baseline.  And has set sustainable levels of take (Sustainable Diversion Limits) accordingly. 

When you add in the environmental water recovered before 2009, by 2019, the year when the Sustainable Diversion Limits will be in force,  over 3500 gigalitres of environmental water will be available for purposeful and targeted environmental watering,

Determining sustainable levels of take in a highly variable system is challenging.  The first point I'd like to make is that the limits are long-term averages, varying yearly according to prevailing climate conditions.

To cover the breadth of the climate zone and different systems of the Basin, we assessed water needs at 122 indicator sites. 

We tested water flows at these sites under current arrangements, and near natural (or pre-development) conditions, and under three scenarios of water recovery (2400, 2800 and 3200).  These scenarios were modelled under the existing rules and constraints of river management.   

And to assess performance of each of the scenarios against all the variability that has been experienced by the system we modelled across 114 years of past climate data. 

This time series includes a number of climate extremes, such as the Federation drought, the Second World War drought and the recent Millennium drought, and the record floods of 1956 and the wet years of 70s. 

  • And I should point out that the recent floods of the past two years are well within the variability of the last 114 years (far below the flood levels of the 1970s). 
  • And the Plan is designed to manage water across the spectrum of climatic conditions, not just in one climate extreme, such as drought, although managing resources to improve resilience through drought is a key objective. 

The key point here is the better we can be at managing our water resources to deal with the current variability in our climate, the better able we'll be to adapt to future climate conditions.

What do we know about future climate change?

Over the past 5 years, the MDBA has collaborated with the CSIRO, the Bureau of Meteorology, the Department of Climate Change and Energy Efficiency and the Victorian Department of Sustainability and Environment to establish the South Eastern Australian Climate Initiative, or SEACI.

SEACI has produced 15 climate projections that extend out to 2030 – these projections use scenarios of local rainfall and potential evaporation to estimate changes in stream flow across the region.

The scenarios range from a 10% increase in stream flows to the extreme dry of a 30% reduction.

While we don't have a firm understanding of which of these 15 projections is likely to eventuate – and we lack certainty about climate trends over the next 5 to 10 years - the range of climate projections has had a major influence on the decision to design a Basin Plan that is flexible and can be adapted to future climate conditions.

The adaptive approach of the Murray-Darling Basin Plan: allows adjustment as climate trends become more certain.

We believe that our adaptive and pragmatic approach is a critical step in adapting to climate change: allowing enough flexibility in the planning process.  Our ability to predict future climate trends is improving all the time, as is our understanding of how climate will affect stream inflows. 

A draft Basin Plan which has inbuilt review and adjustment mechanisms is essential in this situation.  The Basin Plan will be reviewed at least every 10 years, and has the capacity for reviews as frequent as 5 years.  This means that all aspects of the Plan such as sustainable diversion limits, the environmental watering plan, salinity plan, trading rules, and risk management strategies, can be reviewed and adjusted at least every 10 years.  

The review periods allow new climate data, models and forecasts, as well as local knowledge, to be incorporated as these become available.

But the Basin Plan also has mechanisms for continuous adjustment and adaptation:

  • environmental watering priorities will be determined every year with the State water agencies – and these priorities will be adjusted as a result of experience and new information, as well as seasonal predictions. 
  • the existing water allocation arrangements will be continued.  These arrangements have been developed over many years and allow for conservative annual adjustment in response to preceding and forecast conditions - a critical feature of sustainable water management in a highly variable climate
  • creating an unrestricted water market through the Basin Plan trading rules.   An effective water market provides an important avenue for adaptation for Basin industries and communities in the Basin – both to the climate extremes of flood and drought, and to future climate change.  A recent study by the National Water Commission confirmed the major economic and social benefits of water markets and trading.  It was a key factor in helping farmers remain productive during drought.

An important feature of the draft Basin Plan is our proposal for a 2015 review, which gives us the opportunity to adjust the sustainable diversion limits in advance of their proposed enforcement date in 2019. 

The 2015 review provides for a rigorous assessment of the implications of future climate change for the environmental outcomes sought under the Basin Plan – a strong recommendation from CSIRO and one we agree whole-heartedly with. 

But there is an important consideration that is yet to be addressed - that is, what environmental objectives we wish to maintain in a changing climate. 

  • Should the environmental outcomes determined for the Basin Plan based on historic climate be retained in the face of a drying climate trend, or should they be modified proportionally in the same way as will occur for consumptive water users.  
  • While setting out the environmental objectives for management is a critical part of the process, we could hold a 3 day conference on this topic alone, so I'll move on.

To recap: the Authority has:

  • used historic climate variability to develop sustainable diversion limits to improve the health and resilience of the system, and
  • has designed an adaptive framework for the Basin Plan as a practical response to climate change

Is this the right approach?

The draft Productivity Commission report released last week on Barriers to Effective Climate Change Adaptation provides some very useful guidance here.

A key point of the Productivity Commission report is that priority should be given topolicy reforms that help communities, industry and governments deal with current climatevariability and extreme weather events.

This is the space we're in now with water management in the Murray-Darling Basin. There is an urgent need to reform our use of water under the current known climate.

Thesereforms deliver direct community benefits from a more resilient environment, and help build adaptive capacityfor responding effectively to future impacts.

The Productivity Commission is much more cautious in its advice on implementing reforms to address future climate trends.

It makes the point that where there is uncertainty, and where the up-front costs are high, there is likely to be a benefit to the community in deferring action until better information becomes available.

This report has reaffirmed to the Authority that we are on the right path in addressing the current—and pressing—need for reform.  And at the same time creating a flexible and adaptive framework that allows new information to feed into future management decisions.

The Basin Plan, needed now

It's very clear that while there are divergent views across the Basin – about how water should be managed, and how climate change should be taken into account – there is also a consistent message that people want to get on with improving our management of water resources.

We believe the quest to find the “perfect science” on climate change is not a reason to delay making a start in reforming our water use and getting more water flowing into the environment.

Our adaptive framework is designed in a way that allows new science to be brought forward and considered.

A major step in the reform process but it is just a beginning

As an Authority, we need to ask: do we now have enough information to deliver a sound Basin Plan to the Minister to better coordinate and manage water use in the Murray-Darling?

We are very firmly of the belief that we do.

Could we do more work? Yes, we can always do more work. And that's why we've set up an adaptive framework in the Basin Plan to provide opportunities to feed new information and ideas.

And we'll continue working with experts in climate science as part of our future work program.

Our formal consultation period has now ended, but we will continue to seek feedback in finalising the Basin Plan.

We welcome suggestions and ideas for how climate change could be better integrated into water management in the Murray-Darling Basin.

ENDS

For media information contact the MDBA Media Office at media@mdba.gov.au or 02 6279 0141.

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