Trees help reduce the urban heat impact in built environments. Photo www.flickr.com/photos/sdot_photos
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Runoff water, some trees, and a simple device can dramatically reduce urban heat.
Urban heat is an increasingly dangerous killer – and it’s only going to get worse as the climate warms. The good news is that tree cover is one of the most effective ways to cool a neighbourhood: a single tree can transpire hundreds of litres of water in a day, providing natural cooling better than many air conditioners – as long as it has enough water to thrive.
Now, a team of Australian researchers have demonstrated that a trick for harvesting stormwater can make trees even more effective.
The study revolves around a device, called the TREENET Inlet, which can harvest stormwater runoff from roads and soak it into nature strips. This device provoked saplings to grow 65 per cent more in height and 60 per cent more in diameter than control saplings, on strips without the devices.
The saplings with stormwater feeding were then 169 per cent better at photosynthesis during dry months.
According to Associate Professor Huade Guan, a hydrologist at Flinders University, trees with the inlet installed also had cooler canopy temperatures – meaning they were less ‘stressed’.
A paper describing the research is published in Frontiers in Climate.
The TREENET Inlet is a pipe, surrounded by a porous material, about 60 centimetres tall and 30 centimetres wide. It’s installed into a hole dug in a nature strip.
‘Water will be stored there temporarily, and slowly soaked into the surrounding soil,’ explains Guan.
The inlet is connected to the gutter via a small pipe, so it can collect stormwater.
The researchers tested the inlets in Mitcham Council, in southern Adelaide, on white cedar trees (Melia azedarach).
While the saplings grew better with stormwater, mature white cedars could also transpire more water. On average, trees near installed inlets transpired 17 per cent more water – and this rose to 21 per cent in dry periods.
Guan says that the inlets should work similarly well for other types of tree.
‘All trees need water,’ he says. ‘TREENET actually provides more water to support tree growth and functioning.’
The researchers point out that this device, which is now being trialled by other councils, is only one way that stormwater could be used to cool the streets and benefit urban greenery.
‘Increased land surface sealing due to urbanisation and building homes and infrastructure has decreased rainfall infiltration to the soil, decreased vegetation cover and increased demand on mains water resources,’ says lead researcher, Flinders PhD candidate Xanthia Gleeson.
‘TREENET is good for the street,’ says Guan.
‘But I think that in Adelaide, we should harvest more water. We should use other structures and other space – for example, residential gardens. Everybody can install something to retain the stormwater in our landscape.’
This article was originally published on Cosmos Magazine and was written by Ellen Phiddian. Ellen Phiddian is a science journalist at Cosmos. She has a BSc (Honours) in chemistry and science communication, and an MSc in science communication, both from the Australian National University.
Published by The Echo in conjunction with Cosmos Magazine.
So they have invented “Underground dams” and are having to coach it in health and eco terms so that the Extremists on the left don’t shut them down.
I love dams cause they work, even if hidden underground, so I’m on board. It will make our streets look more European.
That’s what towns & cities need…more leafy boulevards! So scenic. So shady. So there’s work in maintaining, pruning etc but look at the advantages!
This is not a new idea. Harvesting storm water runoff is thought to be one of the great untapped sources of an increasingly demanded resource. This water otherwise goes from the impenetrable hard surfaces in built environments straight to rivers or straight to the oceans, causing environmental damage with changed and accelerated flow patters and taking all the urban litter and contamination with it.
Spot on, Liz.
The TREENET Inlet is a good idea. Longitudinal centreline grass swails have been another good idea. (Have been used in Qld for a while)
For Adelaide , they deserve all the shade they can get . They’ve wiped out all their shade out in the country ,never seen so much barren dry dusty sheep paddocks with not a tree in sight ,, and eroded that much that it’s more rocks than dirt and grass . . And that’s close to Adelaide . ……. A great idea tho , keep them coming. … From my magnifying glass observation , it’s a nice well thought out landscape planting , it looks great , a picture . It’s all northern hemisphere plants . . But is it possible to use Aus natives to do that job . The closest that white cedar gets is India , it’s not an Aus native . It’s a great looking tree , and deciduous ,, for winter sun ,, very cleverly thought out. And the box hedge could be Lily pilly hedge ,, and the violets around the base of the tree could be Aus violets or mini lamandra . It’s not that hard . Also we have a really good Aus white cedar and foam bark and a few smaller trees ( large shrubs) 20 ft high that provide plenty of shade and feed the native birds and beasties . Not knocking it,, just tweeking it.