Waiting for the rain

One of the main principles of permaculture is that the ideal garden should require as little human input as possible. Since water usually accounts for the greatest input, catching and retaining rainwater is the best way to minimize what must be put into the system.

There are several ways to go about catching rain. The easiest is to just put a few barrels around the house, one at each downspout. The average roof can catch thousands of gallons of water each year, more than enough to meet the needs of the both the garden and lawn. For fun, you can estimate the amount of water your roof could catch with the following equation:

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([sq ft of ground covered by the roof] x [avg rainfall in inches per year])/12 x 7.5 = gallons per year of rainfall

For our house we calculate (1200 x 35.2)/12 x 7.5 = 26,400 gallons per year! What is so cool about catching rain this way (besides not having to run the sprinklers all the time) is that it prevents the water from running off into the sewer system, and instead helps return it to depleted underground aquifers by slowly percolating it through the ground. Also, using rainwater on the garden is better for the beneficial microbes in the soil, since it is free of chlorine and other chemicals that are meant to kill living things.

We bought a few 55-gallon drums from the Kalona Cheese Factory for $5 each and are planning to place them around the house. The picture above is our first barrel at work. The filter on top of the barrel is a 5-gallon container half-filled with layers of drain gravel, sand, and activated charcoal to take out sediment. It fills to the brim after a 1/2 inch downpour! So far we are using it to water our lawn, indoor plants, and inedible outdoor plants. We will have the water tested for VOCs and other contaminants before using it on the vegetables, since we have a composite asphalt roof that could be leaching badness into it.

Another way to collect rainwater is to catch it directly in the garden by using swales. Swales are 1-2 foot deep trenches placed on a downslope to catch water running downhill, suck it into the ground, and store it there. Everything below the swale needs much less frequent watering, because the plants can constantly draw from the large lens of water that forms under the soil. We will put in 3-4 of these around the backyard, which is entirely downsloping, and will plant accordingly (drought-tolerant plants above the swales, water-loving plants below). Here is the beginning of the first swale in the veggie garden. It will be filled with layers of drain gravel, mulch, and straw.



Yet another way to suck water into the ground and keep it there is by planting a rain garden. This is usually a concave area near the street that is planted with native plants with long roots that quickly drink up the water and store it in the soil. The garden catches the rain before it runs off into the sewer and eventually returns it to an underground aquifer. We will tackle the rain garden once the weather warms up again in the spring. Until then, here is an example of what it will look like: