In 2002, a landmark decision was made to invest $700 million (AUD) to recover 500 gigalitres of water to restore the iconic River Murray south-eastern Australia. A cornerstone of this initiative was the construction of pumps, regulators and levees to deliver water onto the floodplain.

We are now embarking on a more ambitious $12+ billion restoration program to recover an additional 2750GL. Building on the success of the River Murray initiative and recognising the potentially significant impacts to rural communities, it has been agreed that the target can be reduced by up to 650GL where equivalent environmental outcomes can be achieved through the use of works.

Can this be done? The political stakes are high – livelihoods can be dramatically affected and lots of cash is on the table. The scientific challenge is immense – the method to assess the ‘equivalence’ must be defensible and yet there is limited experience in the use of large scale works to base it on. This paper explores the lessons learnt thus far and the technical and political challenges we face as we embark on the largest river restoration project in Australian history.