In the second of a two-part series, Dr Tom Young, STRI technology manager and green roof consultant, discusses how green infrastructure can be used to help store stormwater on sites and how that can be linked to sports turf surfaces.
Here’s a transcript of the video.
That’s all great, holding the water on site on the roof like in this example, but a lot of situations that’s not always appropriate, or you might not be able to hold on to all the water. So, what else can we do to store water around a building or a site? What we’ll do is demonstrate what else you can do and if we have another rainfall event on the standard roof, what we’ve got here is a hose pipe so what we’re doing is harvesting the water from this and we’re now piping it into a storage tank over here.
This is very similar to a standard garden water butt and the principle is exactly the same where we’re taking water and instead of letting anything that does drain off the roof, we’re now going to store that elsewhere on the site. What we’ve got here is a tank that represents a standard rootzone. We’ve done a standard sport rootzone here, but this could be a raised bed or just a standard flower bed.
What we’ve used is a geocellular drainage layer which can connect together to make tanks, and you can see we’re piping the water in and that’s now starting to be stored in this tank. So that water can now be stored below, for example, on a football pitch or a flower bed or even a car park, and this system is very adaptable and can be utilised in lots of different situations.
What we’ve also got here, and you’ll notice the blue food dye that’s moving up the profile, is the ability to have passive irrigation from this system. This is where we utilise cones that are in the geocellular matrix that wick water from the storage into the rootzone, and they take advantage of waters natural ability to want to move upwards. That’s one of the reasons why trees can grow so tall is that once one water molecule goes up, it pulls the other one up after it, and that’s called capillary action. So you can see here, the water over a period of a few days has risen up in the profile and generated essentially a hanging water table which the plant can then obviously use.
You can see this system is used as below ground irrigation, so you’re watering the plant from below which is much more efficient than watering from the top. STRI has done extensive trials in Australia on sportsturf that have shown water savings of between 30 to 60%. Now that’s not to say you’re completely replacing overhead irrigation in a sportsturf application, but you’re seriously reducing the amount of water needed when you do apply it from above. So that’s one application on sports turf.
Also, for example, you can have one of these in a raised bed in a development or in a green roof and that’s what STRI have also done. A lot of work at the moment is designing these types of systems on roofs to reduce the amount of water that comes off them, but at the same time reducing the actual water needed to grow the plants.
So just to go through the system in a bit more detail, what you have here is the tile called a Permavoid tile. This is a geocellular system that can be used as sub-base replacement. In a sports turf situation, we would use that to replace the gravel drainage layer. On here, this is your water storage area and if we wish to have irrigation what we will do is utilise these cones here and we put wicks in.
What they do is they sit in the drainage layer and any moisture that is there or excess moisture that is there suck up into the rootzone. Then we also have to have a high spec geotextile and what that does is prevents rootzone from going down into the cell, but it allows water wicked up through those wicks to spread evenly across the system. You’ll see over here that the rootzone is evenly wet due to the geotextile spreading the moisture evenly through the rootzone.
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