Climate change and the draft Murray-Darling Basin Plan

Jamie Pittock

The Murray-Darling Basin Authority's (MDBA) draft Basin Plan does not adequately fulfil the obligation under the Water Act 2007 to deal with the risks posed by climate change to the availability of Basin water resources. To rigorously manage the anticipated impacts of climate change on water resources and ecosystems, three approaches are required.

Firstly, reductions in water allocations to account for potential losses due to climate change. CSIRO modelling suggests that between 1990 and 2030 the average surface water availability in the Basin could increase by up to 7% or decrease by as much as 24%. These impacts are magnified down the rivers, and in the worst case scenario, outflows may fall by up to 69%.

The Authority has erred in adopting the CSIRO median scenario of a 12% reduction because this is no more or less likely than other outcomes and because good risk management requires considering how to manage the consequences of less likely by more severe events. There are three ways in which the draft Basin plan could do this:

• Increase the amount of water allocated to the environment. The MDBA say in the draft Plan that they will manage the risk of climate change by implementing their plan. In the Guide to the Basin Plan in 2010, the Authority proposed to reallocate 3% of diverted water to the environment over a 10-year period for adaptation to climate change compared to a total reallocation of 27-37%. This volume of water is not adequate to ameliorate the impacts of a climatic step change, such as that experienced in south-west WA. However the draft Plan reduced the total reallocation to 2,750 GL/year of water to the environment (25%), suggesting that any climate change consideration has effectively been eliminated.
• Ensure that the environment does not continue to suffer disproportionate cuts in years of reduced water availability. In the Guide the MDBA adopted a policy of 'equitable sharing' of water losses between the environment and consumptive users. While better than the status quo it does not fulfil the Ramsar Convention obligation to give priority to maintaining the ecological character of wetlands. Further, equitable sharing is not guaranteed in the Plan as the details on implementation are left to state government water resources plans due in 2019.
• Review the plan frequently enough to adjust water allocations to climate changes. Reviews of the Plan are proposed for 2015 and in the lead up to a second Plan from 2021 which could fulfil this ideal. However the proposal to begin implementation of the Plan from 2019 militates against timely action.

The second necessary measure to manage the impacts of climate change is the application of adaptation measures. The draft Plan only proposes to use environmental water allocations and measures to sustain wetlands. Environmental flows are an important solution but both of these measures only work with good management that has been lacking from our state governments.

Environmental flows should be complemented by a range of additional interventions that have different risks and together spread risk to reduce the likelihood of unacceptable impacts. These complementary measures include protecting remaining free-flowing rivers, replanting riverside forests, removing redundant dams, and adding fish ladders and cold water pollution control devices to dams. These measures are not considered in the draft Plan.

The third necessary measure to manage the impacts of climate change is to regulate climate change-related inflow interception activities to prevent further loss of water. The total volume of water diverted from the Basin continues to increase as poorly-regulated activities take more water. These include forestry plantations, farm dams and take from overland flows. New climate change-related energy and sequestration activities threaten to exacerbate this trend, including from carbon farming methodologies and gas production.

Under the 2004 National Water Initiative these were supposed to be identified and regulated within the water market where they have a significant impact, but only South Australia has taken action. The draft Plan merely proposes that states are to 'identify' these inflow interception activities by 2017 for incorporation in water resource plans from 2019.

In conclusion, the draft Basin Plan does not propose adequate measures to manage climate change impacts. Three major changes are recommended for the Final Plan: reallocate more water from consumptive uses to the environment; cap water consumption by unregulated users and incorporate them in the Basin's water market; and spread the risk by adopting complementary adaptation measures.

Dr Jamie Pittock works at the Crawford School of Economics and Government, Australian National University.