Josiah Cain, a landscape architect and water-systems expert based in Marin County, California, is best known for his work on San Francisco’s California Academy of Sciences ― he helped create its spectacular 2½-acre, native plant–covered living roof. But he’s also worked on many smaller-scale residential projects that are water-wise and beautiful.

Why gray water in the garden?
We need to take advantage of water multiple times. Technically, we know everything we need to know to recycle gray water in an efficient, safe way. But gray-water policies vary wildly from state to state ― some have no policy, others give permits on a case-by-case basis. Culturally, we’re in the Dark Ages.

Is rainwater harvesting easier than gray water?
Absolutely. It’s technically feasible, and most regulators are comfortable with it. The only drawback with rainwater harvesting is that water is
so cheap [0.00285 cents per gallon in Denver, for example]; it’s hard to get it to work as an investment [$1.50–$4.50 per gallon, depending on installer and whether setup is above- or belowground]. It’s for people who can afford it.

Is water too cheap in the West?
Tier One water, for basic needs, should be cheap. But Tier Four, for the most aggressive water uses, should have higher prices to encourage conservation. Without financial incentives to use rainwater and gray water, many people won’t.

You grew up near Northern California’s Trinity River. How did that affect your work?
Living where most of the state’s water comes from, and having a connection to that ecology, was important. I grew up chasing salmon on that river. They’re no longer there.

Glossary

Gray water Recycling home wastewater (from laundry, dishes, and bathing) for use in toilets and gardens; works with a home purification system.
Living roof A waterproofed roof covered by a lightweight growing medium and planted with vegetation; reduces rainfall overflow that’s lost to storm drains.
Rainwater harvesting Using a storage system (generally a storage tank and piping) to collect rain and pipe it to house and garden.
Water "tiers" A growing number of water agencies use tiered rates to discourage excessive use. They generally charge the least for a base amount ― what you’d typically use indoors, for example. After that, the more water you use, the more expensive it gets.

Next: Southwest-based landscape architect Christy Ten Eyck

Southwest-based landscape architect Christy Ten Eyck shares advice on shaping an arid garden.

When you design an arid garden, where do you start?
A lot of thought goes into making the path of water sacred. That is, to not let the rain that runs off the roof spill out into the street. Slow it down. Create places for it to collect.

How do you manage rain-water?
You can do a lot with grading ― swales, berms, basins. Or you can install a series of gentle terraces. I like permeable ones such as dry-stacked stone, gabions, living walls. They behave like check dams but look more artistic.

What else can we do?
Shade, shade, and more shade. Don’t stop with the patio. You want some tree canopy to soften that transition area between deep shade and harsh sunlight. If you provide enough natural shade, you won’t need to add thirsty plants (like hydrangeas) or fountains and ponds to feel cool.

How can we add water features without being wasteful?
I like the brimming effect ― water spilling quietly over the edge of a simple basin and recirculating. It’s using the least amount of water for the most effect.

Glossary

Arid Garden A landscape with plants suited for a dry climate. Shade structures and water create cooler, more comfortable microclimates. Basin A bowl-like depression in the soil’s surface.
Berm A mound or low wall of earth.
Check dam A small dam across a swale, channel, or dry streambed that slows rainwater runoff.
Gabion A rock-filled wire cage, often used to make walls.
Swale A low-lying stretch of land that gently moves water from point A to point B.

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