Cisterns and Rain Gardens

One of my cousins, in Brisbane, Australia, tells me that every new house built there has to have a water tank attached of at least 5,000 liters (approx 1320 gallons).

We have a 320 gallon rain barrel in the backyard, fed by runoff from the garage roof. The volume of water, while fantastic, is simply insufficient to replace sprinklers in this climate. I need something more for the fruit trees and vegetables (it’s not for drinking).

So what about a cistern below-ground? That’s what they have done in the Middle East for millennia (photo) and they are common in many countries today, mostly above ground.

Since we are planning to replace the driveway, one option I considered was building a cistern under it, fed by runoff from the roof. It would have needed a pump to relay water to the garden. But it may be better to build the cistern under the garden itself. Once upon a time that’s probably where the septic tank was. It would still require a pump but my wife will stop worrying about the driveway collapsing. The technology is well known – many restaurants have tanks for their waste vegetable oil storage and this is not that different. I plan to put a small pond above part of the cistern and then more native plants around that.

In “green” parlance the pond and those native plants would constitute what is known as a Rain Garden because it is a slight depression designed to catch rain water once the cistern is full. If you are interested, the Tree People and LA City Council websites are useful resources. Start here and here (pdf) and poke around. Or you can use Google Images for “Rain Garden” and see what it pulls up.

Photo: Istanbul Cistern by Cirua in Wikipedia – it was built in the 6th century.