Ask the water-saving experts

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