A collaboration between eWater Group, CSIRO, and the Murray-Darling Basin Authority (MDBA) is changing the way Australia understands how water moves through rivers during dry periods, a breakthrough for sustainable water management across the Murray–Darling Basin and beyond.
The joint paper, Variable Loss Dynamics for Low Flow Simulation in Source via the AARS Plugin, was presented by Rebakah May, eWater Hydrological Software Engineer, at the Engineers Australia Hydrology & Water Resources Symposium (HWRS 2025) in Canberra in November 2025.
The project combines science, technology and policy under the Murray–Darling Water and Environment Research Program (MD-WERP), a five-year Australian Government initiative supporting research to improve how water is managed in the Basin.
When Every Drop Counts
The Murray-Darling Basin is Australia’s largest and most important river system. It stretches across four states and the ACT, supporting millions of people, agricultural production, and unique environments.
But the Basin is also one of the most complex and stressed river systems in the world. With a changing climate, many regions are facing longer dry spells and declining river flows.
As competition for water increases, understanding exactly how much water moves through a river, and where it goes, becomes critical.
Traditional computer models simplify these natural processes. They estimate how much water is lost as it travels downstream but often miss how the river’s past conditions, whether it has recently been dry or wet, influence how much water is absorbed into the ground or evaporates.
That means the models can sometimes overestimate how much water reaches downstream communities or the environment, especially in dry times. For water managers, that uncertainty can make it harder to plan environmental watering, manage drought impacts, and share water fairly.
A New Way to Understand River and Groundwater Connections
To solve this challenge, scientists at CSIRO, working with MDBA, developed a new modelling approach called Alluvium as River Storage (AARS) under the MD-WERP program.
In simple terms, AARS treats the material beneath and beside a river – the sand, gravel and groundwater – as a kind of sponge that can soak up or release water depending on how wet it already is.
By building this memory into models, AARS helps them reflect real-world behaviour more accurately, showing how rivers lose or gain water depending on previous conditions.
When tested in CSIRO’s AWRA-R model, AARS was able to better reproduce observed low-flow events in northern Basin rivers such as the Border Rivers, Gwydir and Barwon–Darling, compared to more traditional loss methods.
From Research to Real-World Use
To bring this scientific advance into everyday water management, eWater Group worked with CSIRO and MDBA to integrate AARS into eWater Source, the national river system modelling platform used by Basin governments, consultants and researchers.
By creating AARS as a community plugin within Source, the new model can be easily added to existing projects, allowing practitioners across Australia to apply the latest science without changing how they already use Source.
Testing on the Macintyre River confirmed that AARS behaves consistently with its earlier implementation, while maintaining realistic results even in complex modelling scenarios.
This also marks a first for Source: AARS is the first groundwater model integrated as a community plugin, giving users flexibility to test and refine the tool while ensuring compatibility with Source’s core framework.
Why This Matters
The improved AARS modelling approach will help water managers and decision-makers to:
- Plan and share water more fairly between states, communities and the environment.
- Protect ecosystems that depend on low flows for survival.
- Plan for droughts and extreme climate conditions with greater confidence.
- Use the latest hydrological science through a tool that’s open, transparent and accessible.
This collaboration showcases how combining scientific research (CSIRO), policy expertise (MDBA), and hydrological software innovation (eWater Group) can turn complex science into practical tools that benefit communities and the environment.
Looking Ahead
While the new AARS plugin already provides significant improvements, the team will continue exploring how the approach could be built even more deeply into Source. That could further strengthen how models capture the link between surface water and groundwater, a relationship that’s crucial for managing the Basin under future climate pressures.
For now, the AARS plugin offers a robust and ready-to-use solution that bridges the gap between research innovation and real-world decision-making.
More Information:
Variable Loss Dynamics for Low Flow Simulation in Source via the AARS Plugin
Presented at the Engineers Australia Hydrology & Water Resources Symposium (HWRS 2025), Canberra, November 2025. Head to CSIRO website for more: Commonwealth Scientific and Industrial Research Organisation, Australian Government – CSIRO
Authors: Rebekah May, Sudeep Nair and Tom Roberts (eWater Group); Shaun Kim and Russell Crosbie (CSIRO); Jahangir Alam and Alistair Korn (MDBA).
Supported by: The Murray–Darling Water and Environment Research Program (MD-WERP), funded by the Australian Government. Learn more about MD-WERP: https://getinvolved.mdba.gov.au/murray-darling-water-and-environment-research-program
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