Last week, we kicked off our first public meetings after the release of the draft basin plan. I say this because we have been consulting with communities, individuals and representative groups since February.

The formal part of the public consultation started in St George, Queensland and Murray Bridge, South Australia. It was a great opportunity to get back-to-back perspectives from both ends of the basin. This week we met with communities in Shepparton and Griffith, and we have meetings in Deniliquin today. But it won’t stop there and throughout the rest of the 20 weeks of consultations on the draft plan, I will be meeting with more basin communities to hear their ideas, concerns and work towards getting the best starting point for water reform in the basin.

As we continue on the consultation process, I thought I would take the opportunity to address one of the concerns that has continually been raised — and that is how we came up with the proposed limits on water use. As anyone following the debate will no doubt know, we are proposing that 2750 gigalitres per year of water need to be returned to the environment. Already there have been significant efforts to recover water for the environment, which means there is 1468 GL/y left to be found by 2019 to meet this target.

But how did we get to the target of 2750 GL/y?

Well, working out an environmentally sustainable level of water use for a basin that is greater in size than the combined area of France and Germany is not an easy task. It is complex and challenging. It involves looking at a diverse range of environments, catchments and communities, which are all connected to one another.

There has been a long history to determining the environmental water needs of the basin, which dates back at least as far as the early 2000s when work first began on The Living Murray initiative. However, for the sake of brevity, I will just go back to a little over 12 months ago to the release of the Guide to the proposed Basin Plan which built upon much of this work.

When the guide was released in October last year, it suggested that between 3000 and 4000 GL/y of water needed to be returned to the environment. These numbers were based on a simple assessment that aimed at achieving a minimum of 60% of flows at the end of each of the major rivers in the basin, in the expectation that this would be enough water to support the basin’s environmental values. Given the simplicity of the method, it was useful for an initial assessment but lacked the necessary rigour for the draft basin plan.

Instead for the draft plan we returned to a method that the MDBA has been developing since 2009. Called the “hydrological indicator site method”, it involves looking at the environmental water needs of sites ranging from large floodplain wetlands (such as Narran Lakes, Macquarie Marshes, Lower Murrumbidgee Floodplain, Barmah-Millewa Forests) to small points along the length of the basin’s river channels. For these selected sites, environmental objectives and water requirements have been identified. Together, these sites combine to build a picture of the environmental water requirements of the basin’s environment.