Agriculture Reference
In-Depth Information
Collecting Rainwater
Before we look at irrigation, let's first look at how we can save water. The first method is
rain harvesting. While a rainwater barrel is a good starting point for water conservation, I
find it interesting to actually run the math and see how little water they hold. I wonder if
they are taking the limelight away from more important methods.
Heide Hermary of Gaia College showed me this. If your roof is 1,000 square feet (93
square metres) and you get one inch of rain on a spring afternoon, you'll have 625 gallons
of water coming off that roof. Where I live, one inch of rain is fairly common during a
storm.
Let's say you're collecting that rain into only a 60 gallon rainwater barrel. It will get nice
and full and you can use it to water your tomatoes another day, but 90% of that rainwater is
going elsewhere, maybe into your city's storm drain system. Your barrel can only take 1/10
inch of rain from that 1,000 square foot roof, so while I like the 60 gallon rainwater barrel,
I think there are better solutions, especially if you have long dry spells during the summer.
A 600 gallon rainwater cistern could handle almost a full inch and a 1,500 gallon cistern
could easily take two inches of rain. Think of it as a giant rainwater barrel. Ideally, almost
every house would have one of these, the size dependent on the amount and seasonal pat-
terns of rainfall in your area. If you don't like the sight of them, they can be cleverly hidden
or even buried.
The thing is, they can also be expensive. A more attractive and potentially less expensive
solution would be to build a small pond, bog or rain garden into which you can direct the
roof water. A pond the size of a king-sized bed and four feet deep should hold an inch of
rainwater off the roof. If constructed thoughtfully, it can also provide drinking water for in-
sects and animals. Most gardens should have some open water for this purpose, with places
for insects to stand while drinking so they don't drown. Mosquitoes aren't a problem if you
keep the water moving and use larvae control methods.
