Rainwater Harvesting Made Simple

 Excerpted from the article "Reaping the Rain" by Andrea del Moral  in Dam Nation: Dispatches from the Water Underground, based on an interview with our good friend,  Brad Lancaster.

Sourcing the Rain

On any house lot, there are three potential sources for harvesting the rain. The easiest to capture is the rain that falls on the yard. Shape the surface of the soil to slow down runoff, raise paths and patios, and sink all planting areas to capture the flow. Choose plants -- primarily low-water-use natives -- that can absorb and hold that water in their root systems. Brad's yard is an undulating series of basins all contoured to welcome, catch, and hold every drop of rain that falls on the property. This means that rainwater doesn't run off into the street, where it would be swept away with motor oil to be further polluted in the sewer system or discharged directly into a local waterway.

The street waters the street trees! See www.HarvestingRainwater.com for more. Drawing by Annie Danger.

The second source of rainwater is the street. Streets run a little like rivers: Brad's asphalt watershed begins at the stop sign on the corner. The road has been graded so that water flows to the curb and then runs down the gutter to distant storm drains. The 20-foot strip between the street and the property line "was just bare earth," Brad explains. "We wanted to turn it into a walkway. So we got people to park on the street rather than the right of way, then dug sunken basins and planted the trees. Wherever there was an existing driveway dip, we directed that water in by creating a small swale [raised mound] on the downhill side of the driveway and making the basins a little lower than the street. We've got raised path ways between the basins, which keep the water from going from one basin to the next. The water that enters the basin infiltrates the soil, rather than erosively running over it. We keep all that water in public property so there's no water rights issues; we're not taking public water out of the public domain." Nineteen low-water-use native shade trees and numerous native shrubs, wildflowers, and cacti use the street runoff to beautify and shade the footpath and the street.

The third source of rainwater is the roof -- and if you're diplomatic, stealthy, or charismatic enough, your neighbors' roofs as well. To harvest this rain, you need a plan for storing more water than the soil of a small urban lot can hold. Brad's cistern is a modified septic tank (no, never used for sewage!) that holds 1200 gallons of water. It was special ordered, reinforced with rebar, and drilled with holes through the interior baffle so water could fill the whole tank at once. It was then delivered with a crane. That's a lot of trouble for a big concrete bottle of water. But the Lancasters are interested in doing things that haven't been done before, especially if it's cheaper and uses recycled or salvaged materials. The tank, with modifications, cost $600; a smaller, commercially available water tank costs over $1,200.

The cistern sits near the house and has a colorful mural painted on the side. Rocks stack up around the base, and plants grow in the cracks between them. It takes up a lot of space, but then, "This is not just a tank!" Brad exclaims. "This is right on our property line so it's also an eleven-foot section of fence. There's a rental unit on the other side with a bay window. There used to be a tenant who would hang out in his underwear and watch everything that we did. We wiped him right out of the scene and then we planted the other side, so he still had a view . . . It's just a different view."

Much of the roof water gathers in the gutters and runs to a pipe, which funnels into the top of the covered tank. Near the bottom, a Y-valve and garden hose send water to the garden. Since most of the plants in the garden are natives, they don't need to be watered at all. A twice-weekly dose of stored rainwater allows the salad greens, squash, and tomatoes to survive the frequent dry spells.

The north slope of the roof has no gutter. Water runs off the house and a nearby garage workshop into a small garden bed. The plants here -- fig trees, orange trees, and squash -- need a lot of water, which they get from the roof in the rainy season. The garden is covered by a black mesh shade cloth that cuts out 30 percent of the light, which reduces evapotranspiration, and thus the plants' water needs. In the dry season, ABS pipe runs to upside-down buckets buried in mulched basins, slowly distributing greywater from the laundry machine to the roots of the plants.

For more, much more, read Dam Nation: Dispatches from the Water Underground.