Dr. Margaret Shanafield from Flinders University (Adelaide, New South Wales, Australia) has led a new report on the state of non-perennial (seasonal, intermittent) rivers and streams that have been built on by successive governments in arid regions such as Australia and parts of rural USA. The report issues a stark warning against the continuing development of housing estates on these lands that is exacerbating already-threatened water supplies, particularly though not exclusively in arid regions. On World Water Day 2021, Politika News (virtually) sat down with Dr. Shanafield to talk global water supplies and the effects of the climate crisis on her homeland, Australia.
The latest report you have led on behalf of Flinders University gives a stark warning about the consequences of building on non-perennial (intermittent) rivers or streams. What effect is building on this type of land having on water flows?
Our study identified both the range and the common features of non-perennial rivers globally. Most people think of non-perennial rivers as purely a thing in dry climates – desert streams, perhaps – but they occur in every type of climate on earth. We also identified ten key topics related to our understanding of these rivers that require more scientific research to be properly understood. These topics range all the way from “What physical processes cause these rivers to start flowing?” to “How much water gets through their streambeds and recharges our groundwater?”. That’s not to say that these things haven’t been measured in certain locations, but we don’t have a solid, overarching understanding of how they work.
As our global population expands, our cities get bigger, and there are more people to feed, so too does our need for water. This is causing rivers that used to flow all year to become non-perennial. At the same time, we are building larger cities in more dry climates, and many of the streams in these areas are channelized or covered over. Of course, this alters the hydrology in those areas, affecting groundwater tables and vegetation in the region.
Why are non-perennial rivers and streams so important to the water supply in arid (and other) regions, such as Australia?
Over 70% of Australian rivers, including long reaches of our most important river basin, the Murray-Darling, are non-perennial. These rivers are the lifeblood of many of our cities and towns, and the groundwater recharge that takes place through their streambeds refills the aquifers we pump from. Without these rivers, Australia would be uninhabitable.
Why do governments choose to build on non-perennial rivers and streams? Why is this dangerous for residents and the surrounding environment alike?
In many semi-arid and arid regions, streams may flow only for a few months a year – or even just a few days a year. There have been studies that show that people think about these streams differently, and I think sometimes people even forget they are streams when not flowing. Only during big storm events are we inconvenienced by flows in these streams and forced to acknowledge their existence. Moreover, as our cities continue to grow, there is a lot of pressure to use every square meter of space, especially flat space! So if there was an area of a city that was historically left clear because it was swampy, it becomes more and more tempting to build over it, regardless of hydrology. Engineers can fix any of the inconveniences of nature, right?
Yet big storm events such as 50 or 100-year rains actually have the same statistical chance of happening every year. And when it rains, the water has to go somewhere – and usually wants to go where it always went. So building on top of them opens residents up to flooding and heartache. It also opens up the potential for social injustice when those with less money end up only able to afford the flood-prone areas.
New South Wales is currently experiencing horrendous flooding with officials describing it as a ‘one-in-a-50-year event’. Firstly, is this event being made more extreme by the problem your report explores? And what difficult, science-backed decisions does the government need to take in order to prevent fatalities due to flooding in the future?
We study rivers that dry; a lot of studies are finding that these rivers are going dry more frequently and over longer stretches. Australians have experienced this repeatedly over the past few years. Perhaps one of the factors making this flooding so hard for people is that it comes directly on the back of drought and bushfires. As they say “when it rains it pours” – in this case it feels like natural disasters keep pouring down. However, even in the face of all these natural disasters, we fail to think about (and act to limit) climate change and the increasing role of extreme weather predicted around the world (including, of course, Australia) if it isn’t checked.
If no changes are made to the level of residential building on non-perennial rivers, and the decline in river-flows that is currently being recorded continues to get worse, what are the potential consequences for human life and the planet?
Well, all living things need water to live. So when our rivers don’t flow the ecosystems along them can’t survive – including the human communities along them. There are ample examples of civilizations that have failed due to their rivers drying up.
As a separate issue, when we build along rivers (whether perennial or non-perennial!) we have to give them some space. Rivers naturally flood their banks on a regular basis, no matter how hard we try to control them. Again, with more extreme weather events predicted in our evolving climate, the chances that even ephemeral rivers will periodically flood seems probable.
In your report you talk about the effect of evapotranspiration on water supplies. What does this process look like and how is it being affected by human-driven global warming?
Evapotranspiration is the use of water by plants and trees. Some of the water they use is transpired through their leaves, just like humans sweat (though for quite different reasons!). As the climate heats some parts of our planet more, it’s predicted that evapotranspiration in those areas will increase. This could result in higher use of water along river corridors, though it’s not something we have researched.
Finally, given the crucial but sobering research you do, do you find yourself hopeful for the future?
I have to be hopeful that life will be good for the next generation – I have two little kids. I am hopeful that by better understanding our planet we can do a better job of taking care of this awesome planet we inhabit. Science is absolutely crucial for the human race. The planet will, in the long-term, be fine – on a geologic timescale we are just a blip. But how long humans are around is dependent on our understanding of how this place works and how well we can keep conditions within the range that humans can tolerate by not overstepping certain limits. Science helps us figure those limits out.
Politika News would like to thank Dr. Shanafield for her time. Readers can find the report led by Dr. Shanafield here.