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Common challenges across water resource plans

The 33 water resource plans being developed under the Basin Plan will for the first time enable the entire Murray-Darling Basin to be managed as an integrated system.

The Murray–Darling Basin is a complex network of connected rivers, streams, floodplains, lakes, wetlands and groundwater.

There are a range of challenges that are common across all water resource plans, including:

  • changes to baseline diversion limits
  • climate change
  • connectivity.

These challenges are considered by Basin state governments and the Murray–Darling Basin Authority in developing and assessing water resource plans.

Baseline diversion limits and the Basin

Water management in the Basin is changing. As part of this transition a new system of water limits begins, replacing the current ‘cap’ system. This next phase is an integral part of implementing the Basin Plan.

The new system will focus on sustainable diversion limits (SDLs). SDLs are how much water, on average, can now be used in the Basin by towns and communities, farmers and industries. Each area also has a baseline diversion limit (BDL), which is an estimate of how much water was used in the Basin, before the Basin Plan – generally these figures represent the level of water use allowed under state law in 2009.

SDLs and BDLs are linked—any change to the BDL will then impact on the SDL. Initial limits were established under the Basin Plan in 2012. Limits need to consider the best available information, and will adjust as new information comes to hand. Improving how water is accounted for will ensure regulation and compliance is robust.

Baseline diversion limits and water resource plans

Under the Basin Plan, as with the current cap system, some diversions are not fully accounted for under the new limits.

Governments are committed to obtaining more information about these diversions, and continuously improving measurement and monitoring—this means the BDL estimates could be improved through the accreditation of water resource plans and in the future.

As part of plan development, the Basin state governments may choose to conduct further modelling, consultation, analysis and measurement to review the BDLs established in 2012 and if necessary, update these for each water resource plan.

Changes to the limits do not mean more water is available for use, this water is being used already—it is just bringing this use into the new system, ensuring it can be monitored, and use does not grow over time.

Further work is being conducted to improve accounting of floodplain harvesting, disconnected streams, farm dams and plantations. In future, these activities will be included in the estimate of the BDL to improve water accounting, but we know this will take some time and may need further adjustments in the future.

Since 2012 we have an improved understanding of how state policies work in conjunction with the Basin Plan and the Water Act.

At the time of Basin Plan development, South Australia’s water allocation plans were being drafted. Their estimates have improved since the development of the Plan and have been applied to the model, which improves the BDL estimate.

When the Basin Plan was developed there were some instances where there was no estimate on how much water was being used. We now have a better understanding of water use in these areas and an estimate has been determined, using relevant data and best available methods.

BDL estimates may also change, as we gain a better understanding of accounting to ensure the system considers the best information and is set up to ensure water is accurately accounted for.

This means the baseline diversion limits are expected to change as part of the development of water resource plans—because better information is available and needs to be incorporated. 

Climate change and the Basin

Climate change and climate variability is shifting Basin weather patterns, rainfall, and river flows. Projections suggest an increase in drought frequency and severity, and at the same time heavy rainfall events are expected to increase.

A shift in rainfall patterns will affect the storage of water and change demands from irrigators and communities. CSIRO warns that outflows at the Murray River mouth in South Australia are likely to be influenced by climate change by 2030.

The Basin Plan sets sustainable diversion limits, which limit how much water can be used, to ensure there is enough water to sustain natural ecosystems.

Water management practices in the Basin take into account climate variability. Water is allocated based on availability. In a wet year, more water will be available for use compared to a dry year.

The environmental water holders consider climate variability when planning use of their allocations, and the MDBA also considers climate in setting out the Annual Environmental Watering Priorities.

The Basin Plan has been developed to ensure climate variability and climate change is considered in real-time, and climate change patterns, measured over decades, are considered through regular reviews.

Over the coming years, the MDBA will be conducting and coordinating research to inform the Basin Plan review in 2026. An important focus of this research is understanding the future implications of climate change on our water resources.

Climate change and water resource plans

The current state-based systems of allocations to water users remain, with water allocations based on availability and seasonal conditions. The allocation system is an ongoing adaptive method of responding to climate variability and climate change.

Climate change is considered in the development of all water resource plans. The plans are just one of the ways climate change is managed through the Basin Plan.

The plans include a risk assessment, where Basin states consider the risks of climate change and determine their future management responses.

The plans also require Basin states to decide on their management approach to extreme dry periods. Given the predictions on climate change, it is vital that extreme events are planned for and managed appropriately.

The plans ensure Basin states consider the groundwater resources, and protect groundwater-dependant ecosystems. For the first time, under the Basin Plan, Basin-wide limits have been set for the amount of groundwater that can be taken from the Murray–Darling Basin. The plans will help water managers to manage groundwater resources in a variable climate.

The Basin Plan ensures that in times of drought, water is prioritised for critical human needs—across the Basin, water will be provided to communities for drinking and household water, before being allocated for any other use. These measures will be included in water resource plans.

Connectivity and the Basin

Connected rivers are healthy rivers. Connectivity helps native fish, waterbirds and plants thrive, restores habitats and helps fish and other aquatic animals move between lakes, wetlands, rivers and ultimately the ocean. Connectivity is particularly important for native fish populations and recruitment, because many native fish species’ lifecycles are completed at different spatial scales, sometimes in different parts of the Basin.

Connecting the rivers improves water quality, and flushes salt, nutrients and sediment out to sea. All water users benefit when rivers are linked across the whole system.

The Basin Plan aims to manage the rivers as a connected system. For the first time, the rivers of the Basin will be managed better within and across state borders, and ensure that the tributaries flowing into main rivers are managed as part of the connected system.

Connectivity and water resource plans

Water resource plans must address specific requirements on connectivity, including clearly identifying the connections for that particular catchment, and clearly set out how these connections will be managed.

When a plan is developed for an area that crosses state borders, Basin states are required to work with adjoining states and ensure all relevant plans have been developed in consideration of the level of water resource connectivity.

The level of water resource connectivity, whether within or across state boarders, will define the range of rules to manage connections that may be set out in the relevant plans.

Groundwater and surface water systems, like rivers and wetlands, can be highly connected and need coordinated management. In developing the plans, states need to consider connections between groundwater and surface water and ensure the health of both systems are maintained.

In the northern Basin, the NSW Government is conducting further work on connectivity as agreed under the Northern Basin Review toolkit measures and subsequent compliance reviews undertaken by the MDBA and Ken Matthews - Independent review of water management and compliance. In response NSW are reviewing management strategies and may revise these to improve flows in the northern basin which could be incorporated into their plans.

In the southern Basin, the connections of the Murray River have been established for many years, and will continue to be managed primarily through the Murray–Darling Basin Agreement.