A fresh look at water management

Back in the 1990s there was a growing recognition that if scientists didn’t start looking at the practical issues around protecting our freshwater systems, both in terms of the quantity and quality of the water, they weren’t going to be there for much longer. That sparked my interest: how do you manage freshwater systems in a sustainable way? 

I had always been good at chemistry at school, but the thought of spending my life wearing goggles and stuck in a lab wasn’t really appealing. In zoology, on the other hand, we went on all sorts of field excursions at university, which was rather more exciting. I now get to combine the two fields.

The hard science I’ve done mainly looks at chemical tracers, particularly stable isotopes, sampling everything from micro algae – the smallest of lifeforms – right up to the biggest predators. When aquatic plants are photosynthesising and taking up nutrients from the water, they end up with a particular signature in their tissue, which we can measure with a mass spectrometer. When an animal eats that plant, they become labelled with a very similar signature. It’s the old adage: you are what you eat. This way we can map the entire foodweb of a river system. It’s a method we use to not only identify what critters are eating, but where they’ve been eating from. It’s a very powerful technique for understanding the major sources of food, and where it’s being produced in the landscape.

I’ve maintained an active interest in this sort of hard science, looking at issues around improving river health. But I’ve also veered into the policy side of things, too, serving as a National Water Commissioner, and currently as a member of the Murray Darling Basin Authority. As a scientist, I’ve always wanted to influence policy and a good way to do it is to get involved in guiding it. 

There’s always been competition for water resources. It’s an intriguing fact that the word “river” shares the same origin of the word “rivalry” – both from the Latin rivalis, to describe the “people who shared the same stream”. 

There’s a growing recognition that whatever we’re doing today we need to do it in a sustainable way – and there will be trade-offs with that. The goal is, really, how do you do all the things that we’d like to do to keep communities and the economy going, but not at the expense of the natural environment? That’s been a big driver for me.

Under a changing climate, the big issue right now is ensuring our catchments are more resilient to extreme weather events. We’ve greatly modified the landscape since European settlement in this country, and our rivers and a lot of the catchments are simply not resilient anymore to these bigger, more frequent rain events. 

Clearly, we need to take a different approach to the way we manage our landscape and our catchments, because it’s ultimately impacting not just livelihoods, but food production, water security – all of those things are threatened. 

We’re realising that it’s not just an environmental problem in terms of land-based pollution, but it’s also a serious economic problem too. For a long time, I believed that if you had the right science, everyone would listen and go, “well, that’s the answer”. But I’ve realised that there’s a whole lot of other things going on that you need to be aware of as well. Increasingly, we’re working in this transdisciplinary space, because you need to be able to quantify what the economic impacts are, and you need to understand the social drivers of change.

Over the last couple of decades, there’s been a growing community interest in restoration projects, fixing up waterways, people planting trees. But it’s not being done at the right scale, and it’s not targeted enough. That’s been one of the things we’ve been working on, developing tools that enable people to identify the best actions to take, and where’s the best place to do them so you get the best outcomes for the least cost. It’s an optimisation problem. We’ve been working on developing planning tools that guide that investment. When you start looking at the economics behind it, you’re going to see that there’s a real economic opportunity for landowners to derive benefit from doing the work – and without landowners, you’re just not going to see the scale of investment that’s needed to tackle the problem.

We understand what the problem is: when it rains, the water runs off our catchments quicker. Stream banks have been cleared so they erode faster. I’m in southeast Queensland, and we know right down to the sub-catchment where all the sediments are coming from that the Port of Brisbane ultimately has to dredge out of their river every year. And it’s productive farmland, a couple of catchments upstream. So we know what the problem is. 

And over the years we’ve also known what the economic cost of that is, in terms of the cost of water treatment, the loss of water storage, the costs of dredging, the potential impact of coastal fisheries – all of those economic factors are understood. And they’re huge. But we’ve still not addressed how we need to fix it at scale. 

It’s not just a case of protecting the natural assets we’ve got. It’s now a case of restoration – and targeted restoration. This is the next big thing. We know most of the pollutant load is coming from a small part of the network. As much as 80% of the sediment and nutrients in the Brisbane River comes from less than 20% of the stream network. 

You can do a lot of well-intended things, but if you’re not doing it the right places, then you can spend a lot of money and get little benefit from it.