By Lauren Roden

Researchers are developing a new method to speed up and improve predictions about floodplain inundation in the Murray–Darling Basin, supporting water managers to make more effective decisions about water delivery.

The floodplain modelling tool is a key part of the One Basin CRC project, Reducing uncertainties and enabling multiple benefits in water delivery operations, which explores how water planning approaches can be enhanced to achieve better outcomes for communities, the environment and industry.

“There are constant challenges in river management to get water where it is needed at the right times, balance water in the various storages, and limit unnecessary evaporative losses – and these plans are made in the face of a lot of uncertainty about things like water availability and demand,” Research Fellow in Hydroclimate Forecasting at the University of Melbourne Dr Tristan Graham said.

“Our aim is to provide a tool that allows water authorities and other operators to understand the potential outcomes of different water delivery strategies to help inform their decisions, which can impact a range of stakeholders.”

Dr Graham, who is based at the Mildura Hub of the One Basin CRC, is responsible for building the rapid inundation model that will provide information about the extent of floodplain inundation.

“Current inundation mapping is high quality, but it can take days and sometimes weeks to produce a single scenario, and it is set up to provide conservative – worst case – estimates of flood extents,” he said.

“Our model will produce results much faster – possibly in minutes – allowing more scenarios or possible inflows to be tested. It will also provide best estimates of flood extents.

“This combination of fast evaluation and best estimation will allow river operators to make decisions based on the probability of an outcome occurring – for example, a one per cent chance of unwanted flooding. Being able to predict inundation prior to making decisions will help them plan coordinated flows downstream and deliberate overbank flows like watering the forest.

“The model can also provide useful insights for other stakeholders, such as forest managers, who are more interested in the likely extent of floods rather than conservative extents.”

Partnering for change

The three-year project, which is in its early stages, brings together a wide range of collaborators, including water authorities, irrigators and researchers, who share the goal of maximising the value of increasingly scarce water.

Australian National University (ANU) researcher Dr Wendy Merritt, who has been acting as project lead, believes having the technical, institutional and governance knowledge and expertise built into the one project is critical.

Alongside ANU and the University of Melbourne, the project’s core partners are Murrumbidgee Irrigation, the Murray–Darling Basin Authority, the University of Adelaide and Water Technology. They are supported by a significant group of affiliate partners as well as other organisations involved in water planning and river operations.

“There seems a broad acceptance that there will be less water into the future, as well as more extreme weather events such as floods and droughts, and that river operators and water managers will need to evolve decisions and operations to achieve intended outcomes for the communities, environment and industries who rely on water deliveries through the Murray–Darling Basin river systems,” Dr Merritt said.

“This project draws on research and industry partner capabilities in technical modelling, integration sciences, and river and irrigation systems operations, and leverages the institutional and governance knowledge of the partners and collaborators, to identify and assess opportunities to enhance outcomes from water deliveries.”

Dr Merritt said the partners’ contribution to the project went well beyond their extensive knowledge of river operations and water management.

“In this space, there has recently been a huge investment in models, tools and governance, and our partners have been instrumental in helping scope our research and find our niche within this packed playing field, where our project outcomes can have greatest impact,” she said.

Proven outcomes

The project’s prototype tools and processes, developed to support water delivery decisions that consider all water users, will be tested through a series of case studies.

The primary case study for the rapid inundation model is the Barmah-Millewa Forest, which is complex in terms of the physical system and the multiple organisations involved in managing the river and allocating and delivering water to meet critical human, environment or production needs.

“The Barmah-Millewa Forest represents a key challenge for river operators due to the reduced flow capacity compared to upstream and downstream, and being an incredible ecological asset, recognised as a Living Murray icon site and Ramsar-listed wetland of international significance,” Dr Graham said.

“River operators have to take many things into consideration when controlling flows through this reach, and their decisions can impact the forest along with many other stakeholders.

“For example, overbank flows during summer–autumn can damage the forest, and water needs to be held high for some nesting birds to successfully breed and hatch their young. Then there are recreational uses – making sure storages and waterways are safe and pleasurable for boating, fishing and camping.

“We want to provide a tool that can help inform their operational decisions and consider the impacts on these other stakeholders.”

When the project ends in 2027, Dr Merritt would like to see that partners have confidence in the tools and assessments developed through the project and are identifying ways to adopt and adapt them to improve their operations and produce benefits for other water users.

She also hopes some of the identified opportunities to enhance outcomes from water delivery can be piloted and further assessed for their feasibility and effectiveness within the life of the One Basin CRC.

Regional impact

The first researcher to be located at one of the One Basin CRC’s regional hubs, Dr Graham said it was a privilege to have the opportunity to work regionally.

“My family and I settled quickly into Mildura and I am certainly grateful for the 15-minute trip to work compared to the hour-and-a-half commute each day,” he said.

“The idea of having researchers located closer to the communities and environments they are researching makes a lot of sense.

“Seeing things in person, and spending time with the people who benefit from our work can give us a fuller understanding of the context of our work and guide us to do impactful research.”

Dr Merritt said the project was lucky to have Dr Graham working in the region from day one, especially as it can be challenging to find people who are the right fit for a job and have the flexibility to move.

“The type of research we are doing in the project does need the researchers to spend time in the regions and communities to understand the situation on-ground and build trust and relationships with those operating or affected by river operations, whether it is through this regional research model or another,” Dr Merritt said.

“Being based in Mildura, Tristan has been well-placed to meet in-person with decision-makers, river operators and community members in the region who have valuable insights about the case study and his work.”