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Water Harvesting on the Cheap

Water harvesting doesn’t have to cost an arm and a leg.

July 19, 2016

When it rains in Baja Arizona, oh, does it pour! Several inches can fall in one hour.

That’s good news if you’re in a natural environment, where 50 percent of rainwater soaks into the earth. What happens to the other half? Forty percent of it evaporates and 10 percent becomes runoff.

If the same storm visits a city—with a high concentration of buildings, pavement, and other impervious surfaces—50 percent of the rain becomes runoff.

How can we capture that runoff? Water harvesting! The goal? To allow rainwater to slow, spread, and sink into the ground. The result? An urban oasis that encourages rainwater to stay around and help us thrive.

Rainwater nourishes trees and shrubs that cool our environment. It feeds fruit and vegetable gardens. With proper filtration, it also can be used as drinking, cooking, and bathing water.

But I’m not going to talk about my rainwater-harvesting cistern. (Don’t have one—too expensive!) Or my graywater-recycling system. (Can’t afford that either!)

Instead, this story is about creating a graywater-harvesting brigade with recycled kitty litter buckets. Refusing to spend money on mulch – and getting a driveway full of it for free. Harvesting bumper crops of beans from an ornery mesquite tree.

As you may have guessed, water harvesting will require some tools. Let’s start with one you already own, your brain. Here’s its first assignment:

Think Like Water

Remember that, regardless of the terrain, water always flows downhill. Do you like where it’s going? Or do you need to send it to some other place?

Next, decide what you want your water to do. Want it to help you grow food? Before you plant that cute little mesquite tree, plant the water first. Here’s how:

Dig a basin, adjacent to the hole for your tree, and build small trenches to direct rainwater to it. Line those trenches with rocks that will slow the flow and prevent the formation of gullies. You’ve just created a water-harvesting feature called a swale.

Now that you’ve planted the water, you might be tempted to put your mesquite in the basin bottom. After all, that’s where the rainwater pool is deepest. Don’t do it! The truth is, trees are like people. They don’t want wet feet any more than we do. So, plant your trees on the basin slope.

Tip: During the summer, our hard, dry soil makes digging by hand nearly impossible. So, embrace technology and use a jackhammer. Don’t know how? In a moment, I’ll show you where you can learn—for free.

Graywater Bucket Brigade

Let’s keep talking about that dry season. Daytime temperatures are scorching, rain is scarce, and your plants are thirsty.

A popular solution is to install an irrigation system and let them drink up. And drink they do. Did you know that, in Tucson, 40 to 60 percent of all residential potable water use is for outdoor plants?

That’s a lot of water. And a lot of money.

So, meet my kitty litter bucket brigade: ready, willing, and able to serve. Basically, I collect used water in buckets, and redirect it outside.

The bucket holds the half-gallon of water that I scooped out of the kitchen sink. The scooper is a recycled yogurt container. Total cost of this system: about four bucks for the organic yogurt—it was tasty—and zero for the two kitty litter buckets. I got them from a neighbor.

What do plants enjoy in their graywater cocktails? I treat mine to the very best in biodegradable soaps, Bio Pac and Oasis. The Food Conspiracy Co-op sells them in bulk and in containers.

Tip: Your best graywater sources are the shower or bathtub, kitchen and hand-washing sinks, and bleed-off water from cooling systems. Don’t pour it directly on plants that you intend to eat, like lettuce and spinach, and root vegetables like garlic and onion. Save it for fruit and nut trees and fruiting plants like artichokes and tomatoes.

Free or Cheap Mulch

In the life of a desert gardener, there are fewer questions sweeter than this one: Want free mulch?

Why do we love ground-up tree trunks, branches, and leaves? Because mulch holds moisture in the soil. It also increases soil nutrient density and controls weeds. In Tucson, you can get free mulch from Romeo Tree Service and Finest Tree Service. Why are they being so nice? Simple economics. Dropping a load of mulch in your driveway helps them avoid landfill tipping fees.

The downside: You can’t call these companies and expect delivery tomorrow. You’ll have to wait until they have a job in your neighborhood. That may be months away. But when they come, look out. Here comes a ginormous mulch pile!

Tip: Use the right mulch for the job. If you’re growing vegetables, mulch your garden with straw. Feed stores sell straw bales for around $10 each. If you’re covering the ground around trees, shrubs, and perennials, use wood mulch.

Lean, Mean Bean Machine

In 2005, I bought a mesquite from Trees for Tucson. It barely reached my shoulders, and now it towers over the house.

The secret to its success? A water-harvesting berm that grows a native plant rock garden while retaining rooftop runoff. My mesquite also produces bumper crops of beans, which I get milled into flour.

The downside: I can’t get near this tree without getting scratched or poked. I’m convinced that it hates me.

Why do I put up with my ornery mesquite? Because I’ve done the math. It shows that one five-gallon bucket of mesquite beans yields around two gallon jugs of flour. Cost per gallon? Three bucks if you’re at a Desert Harvesters event.

Figure that mesquite flour retails for $15.95 a pound, and that a gallon jug holds approximately five pounds of flour, and you’ll realize substantial savings.

Tip: Get up to three natives a year from Trees for Tucson. Per-tree cost is $8 and includes delivery.

Learn More about Water Harvesting – For Free

As a Watershed Management Group Co-op member, you’ll learn by doing. Want to wield the jackhammer I mentioned earlier? A professional instructor will show you how.

The WMG Co-op uses a barnraising model that gets members working to earn labor hours on other members’ projects. When you’ve earned enough hours, the co-op comes to your property. Your only costs are the WMG’s project management fee and the price of materials. Co-op membership is free.

Named for a Victory Gardener who fed eight people from a single plot in Buffalo, New York, Martha Retallick is writer, photographer, and wannabe gardener in Tucson.

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