The future of water management

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From water scarcity to climate change impacts across water management, Associate Professor Fiona Johnson’s research ensures future communities and environments are as resilient as possible to challenges presented by climate extremes. Not only is this work leading to more sustainable and equitable preparation in the instances of flood and drought – it’s creating more robust impact models under climate change.

A/Prof. Fiona Johnson

Although current modelling methods have been used for decades, they don’t accurately take into account the increasing climate risks on water availability. “We know rainfall will change in different ways in the future, so we want to make sure we’re correctly estimating the amount that goes back into the atmosphere via trees versus the amount that ends of up in the streams and rivers,” explains A/Prof. Johnson. “We need models that better understand the real processes because once we have the estimates of how much water is in the streams, we can make decisions on how to share that water equitably amongst communities, environment, agriculture and industry.”

Through the creation of these models, governing bodies can then use a risk framework to best decide how to share water with consideration for further changes in future rainfall.

"“It’s all about how we make more informed and resilient decisions around where and when we use water.”

- A/Prof. Johnson

Local issues with global solutions

Given Australia’s relatively limited historical records and high variability in climate – A/Prof. Johnson and her team have worked closely with governing bodies to help determine the true state of Australia’s water situation. Much of this research has been in partnership with the NSW Government, who develop water sharing plans for catchments in NSW. As part of this process, the Water Group in the NSW Department of Climate Change, Energy, Environment and Water need to ensure they understand the impacts of climate change, and how it can affect water allocations to different users in the catchments.

By looking at methods that could better understand and correct for multiyear variability in climate model simulations of rainfall, A/Prof. Johnson and her team developed software which allowed them to better represent some of the low frequency variabilities in climate model simulations. “We used some really interesting methods called wavelets, which allowed us to look at a time series and break it up into different frequencies,” explains A/Prof. Johnson. “The cool thing about wavelets is that it lets us separate out the day-to-day changes from the long-term patterns and look at them separately.”

Lake Hume on the Upper Murray, New South Wales.

This also saw the team come up with new ways of measuring drought that focused solely on dry periods rather than the traditional approach of analysing both wet and dry. “We developed a new drought index that modified a popular industry measure of water availability,” explains A/Prof. Johnson.

“In our new method we measure the cumulative difference between the amount of rainfall and what is normal for that time of year.” This research has been particularly important within the context of Australia, which regularly experiences consecutive epochs of wet and dry years.

“We have variability as a very distinctive feature of our hydrology, which makes us quite unique.” A/Prof. Johnson.

“This is where a lot of our work in the hydroclimate space has been different from international approaches, because we need to make sure the climate model simulations provide good estimates of that variability and how it may change in the future.”

- A/Prof. Johnson

Prof. Johnson is modelling the Blue Mountains water catchment areas to be able to recommend improvements that will enable us to be more robust against climate change.

A new approach

At the same time, A/Prof. Johnson and researchers in the UNSW Water Research Centre were independently looking at methods to better model catchment behaviour under climate change. “We normally use quite simple mathematical models, and they work pretty well because you can run the models in just a few minutes,” explains A/Prof. Johnson. “But because they’re so simple they don’t really represent what’s happening on the ground in terms of plant growth and soils.”

With this in mind, the hydrology group started working with more complex models that represented changing vegetation and soil nutrients. This research allowed them to look at how well simple models matched the more complicated model when potential future climate scenarios were tested.

This work was also of interest to the NSW Government, leading to further collaborations investigating how best to model the impacts of possible changes in the ways that trees use water in the future. “We’ve set up one of the more complex ecohydrological models for a catchment in the Blue Mountains,” adds A/Prof. Johnson. “We’re then looking at ways to change the simpler models because then you can easily run them for any catchment and try to represent some of the processes that really matter for future water availability.”

Through this research, A/Prof. Johnson hopes to show better ways of modelling evapotranspiration, which would see the Water Group at the NSW Department of Climate Change, Energy, Environment and Water improve rainfall runoff models to be more robust against climate change.

Whether it’s reducing flood risk through informed land use choices or ensuring enough clean water is distributed equitably amongst community, environment and industry – the impact of A/Prof. Johnson’s research is far reaching.

“We all want to live on a planet that’s able to support us and our future generations. We’re only going to be able to do that if we ensure the decisions we make are holistically considered and sustainable going forward.”

- A/Prof. Johnson