The impact of climate change on the Murray-Darling Basin will require a major adaption of the plan in 2026 to allow for more frequent dry periods, which will likely occur on average every five years instead of every 10.
The assessment of the climate risk facing the Murray-Darling Basin plan is included as part of the 2020 review of the progress on the plan, released on Tuesday.
The Murray-Darling Basin Authority (MDBA) is not proposing to alter the plan before its final review date in 2024 but the progress report has flagged that further adaptations to water use are inevitable.
“It is clear that a substantial shift in focus and effort is needed to adapt water management in the basin to climate change – which will reshape water availability and use in the basin,” the report said.
“The unprecedented dry and warm conditions and the associated record low inflows in the basin are an important warning sign to basin communities, interest groups and governments.
“Without the environmental flows provided for by the basin plan, the already devastating environmental impacts, such as the Lower Darling fish deaths, would have been worse. The basin plan and water management arrangements in the basin will need to be responsive to climate extremes in the future.”
Based on modelling by the CSIRO and the Bureau of Meteorology, which is also being released, the warnings in the plan are based on CSIRO’s scenario B. It assumes a two-degree rise in temperatures and a 10% fall in rainfall. But the CSIRO modelled other scenarios with far more dire falls in rainfall.
The MDBA is not proposing any immediate action, even though the current plan does not include the likely impact of climate change, despite there appearing to have been a step change in rainfall patterns in the basin.
The review undertaken by the MDBA essentially amounts to marking its own homework but chief executive Philip Glyde defended it, saying the MDBA had relied on outside input from scientists and consultants and would make as much of the underlying data available as it could.
It has concluded that progress has been made toward achieving the plan’s goals.
“The evidence shows that the basin plan has cushioned the Murray-Darling Basin from the impacts of this most recent drought. Without water for the environment, the impact on the health of the basin would have been more damaging and long-lasting,” Glyde said.
“In the face of climate challenges, we have still seen good progress and outcomes that should be celebrated.”
However, it also identified shortcomings where the plan is lagging behind schedule.
The most obvious of these is the progress on New South Wales’s 20 water resource plans. The plans were lodged more than a year late by NSW and the MDBA does not expect to finalise them until the end of 2021. These plans, which include the detailed rules on how water will be shared between users, are crucial to the plan’s success.
Glyde also noted the states were lagging behind schedule on implementing what are known as the Sustainable Diversion Limit adjustment mechanism projects. These projects proposed by the states, and funded with $45bn of commonwealth funds, aim to improve water efficiency or remove constraints, such as low bridges, that prevent water from being used to assist the environment.
“Until all components of the basin plan are operational, the full benefits for basin communities and the nation cannot be delivered,” the report warns.
The report also puts particular emphasis on the need to make progress on recognising cultural flows and ensuring First Nations people are included in both the planning and processes of the basin plan.
“First Nations, basin governments and the MDBA should develop a practical pathway for the use of water for cultural and economic outcomes,” the report says.
“This should build on current knowledge and fast-track initiatives, such as the $40 million Cultural Flows project for First Nations. Action should be focused on short-term practical activities, as well as build the foundations for enhanced First Nations outcomes in the longer term.”
Glyde said the MDBA was committed to working with First Nations to identify options that enhance outcomes for the large number of communities in the basin.
“The appointment of a First Nations Authority member will help the MDBA collaborate with First Nations to enhance our knowledge of the Murray–Darling and apply this to water management,” he said.
The MDBA said it was also committed to improving transparency and would work to make more scientific data and its models open to all.
Professor Richard Kingsford, a spokesman for the Wentworth Group of Concerned Scientists, said: “There is some really good stuff in the report, but there are some really difficult issues ahead.
“It does tackle climate change – it says it is happening – and to some extent it’s true that opening up the plan and saying we will be revisiting it would be difficult. But there are some serious questions around whether we have the right level of sustainability.”
The current plan was drawn up using historical data on rainfall and flows and did not take account of climate change.
Glyde argues that the plan is one of the biggest and most ambitious in the world.
Among the achievements claimed in the report are that the plan has protected flow regimes across much of the southern basin, delivered positive ecological responses through providing water for the environment and protected some rivers from the worst impacts of the unprecedented drought.
It also claimed success in delivering water to support the Coorong, Lower Lakes and Murray Mouth ecosystems through the drought, substantially avoiding the environmental degradation that occurred during the millennium drought.
But it acknowledged the basin plan was unable to effectively support many floodplain and wetland ecosystems until implementation of critical improved water infrastructure and river operating rules were in place.