Climate change has long been acknowledged as a background pressure on the Murray–Darling Basin. In the 2026 Basin Plan review, it has moved decisively into the core of decision-making, shaping how water limits, environmental outcomes and future risks are being assessed.
The MDBA’s Discussion Paper makes clear that future Basin management can no longer rely on historical climate assumptions. Instead, the review is drawing on updated hydroclimate science to test whether the Basin Plan’s current settings remain workable under plausible future conditions.
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How is climate change being assessed in the Basin Plan review?
Climate risk is being assessed through a structured framework that applies three distinct lines of enquiry. These test outcomes under current Basin Plan implementation, full Plan implementation, and full implementation under a range of plausible future hydroclimates.
This approach is designed to distinguish between short-term climate variability and longer-term shifts in water availability. It also reflects recognition that relying on a single projected future can obscure risk, particularly in a system as spatially and hydrologically complex as the Basin.
What does the latest climate science say about the Basin?
The Sustainable Yields Report, released in late 2025, provides the most comprehensive picture to date of how climate change is expected to affect the Basin’s water resources. It concludes the Basin is virtually certain to become hotter, with cool-season rainfall likely to continue declining across much of the system.
Runoff and long-term average river flows are projected to decrease, particularly in the southern Basin, while groundwater recharge is also expected to decline. At the same time, climate variability is likely to increase, bringing more frequent and intense droughts alongside fewer but potentially larger flood events.
These changes have direct implications for water availability, environmental resilience and the reliability of existing planning assumptions.
Why does this matter for water availability and planning?
Under warmer conditions, higher evaporation and reduced soil moisture mean less rainfall translates into usable runoff. Even without changes to extraction settings, this reduces the volume of water moving through river systems and available to support ecosystems, communities and industries.
For water utilities and regulators, this creates growing tension between long-term planning horizons and increasing uncertainty. Infrastructure, entitlement frameworks, and operational rules designed around historical inflows may struggle to perform as intended under sustained drying.
How are sustainable diversion limits being tested against climate risk?
Sustainable diversion limits sit at the centre of this reassessment. The MDBA’s initial SDL assessments explicitly incorporate climate change as a material risk through the third line of enquiry, which tests outcomes under plausible future climates benchmarked to global warming scenarios of 1.5 and 2 degrees.
Rather than selecting a single forecast, the assessments examine a range of drier, median and wetter futures. This risk-based approach highlights where environmental outcomes may become vulnerable even if SDLs are fully complied with, and where climate change could undermine the assumptions that underpinned the original Basin Plan.
What does this mean for environmental outcomes?
Environmental watering has delivered measurable gains over the past decade, particularly during recent wet years. However, the Basin Outlook Report indicates these gains may be harder to sustain as baseline conditions shift.
Reduced flow volumes, altered seasonality and declining floodplain inundation frequency all place pressure on river-dependent ecosystems. In some valleys, climate-driven reductions in key flow events may limit the effectiveness of environmental water, even where delivery is well planned and coordinated.
This raises questions about how environmental objectives should be prioritised and measured in a future where historical benchmarks may no longer be achievable.
How is uncertainty being managed in the review?
The Basin Plan review explicitly recognises uncertainty as an enduring feature of climate-affected water management. Rather than attempting to predict a single outcome, the assessment framework uses scenario testing to identify where risks are emerging and how severe they may become.
This adaptive management approach aligns with the Basin Plan’s ten-year review cycle, allowing settings to be reassessed as new evidence becomes available. It also reinforces the importance of monitoring, evaluation and transparent reporting as conditions continue to evolve.
The evidence assembled so far indicates that climate change is now being directly tested against Basin Plan water limits, rather than treated as a future consideration.