The Science of Sustainability

Reporter's Notes: Putting Landscaping on a Water Budget

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Is your yard a dated relic of California's water guzzling past, or, an exemplar of the drought-tolerant future that the state's trying to nudge us all towards? Image courtesy of Muhammad Mahdi Karim, www.micro2macro.net.GNU Free Documentation License 1.2

California: This is your new water budget.

In an effort to make plants guzzle less, the state has imposed new restrictions on how much water new and rehabilitated landscapes can use.

For instance, as of January 1st, whenever a developer in California plans a property – commercial or residential – that has at least 2500 square feet of yard and garden, he'll have to tailor the plantings to conform to the amount of water the state deems sufficient for that site. That's where the water budget comes in. More details on the ins and outs of what the state is now requiring can be found here. As I reported in my QUEST radio piece, some California cities are imposing tighter restrictions in hopes of saving more water. Check your city's water efficient landscape ordinance for details.

That being said, homeowners needn't worry that a crew of strapping regulators will be ripping up their front lawns. Existing landscapes won't be impacted by the new rules. But homeowners might wonder how their own landscaping would stack up if their properties were being built today. In other words, is your yard a dated relic of California's water guzzling past, or, an exemplar of the drought-tolerant future that the state's trying to nudge us all towards?

Here's how to figure it out:

Click on this link to get your very own Water Budget Workbook. Choose the tab on the bottom of the page that says "MAWA" — that stands for Maximum Applied Water Allowance.

Choose your city from the list provided. If your city isn't on the list, choose another nearby city that is, but be sure it's in the same "EvapoTranspiration Zone" where you live.

Evapo what?

"Evapotranspiration" is the loss of water to the atmosphere, by evaporation from the soil and plant surfaces, as well as by "transpiration" from plant tissues. A more detailed explanation of what that all means can be found here.

The state's Department of Water Resources and UC Davis developed this beguiling map that divides the state into 18 different zones based on long-term monthly average evapotranspiration. Not everyone in the Bay Area lives in the same zone with local zones ranging from Coastal Plains Heavy Fog Belt to Northern Inland Valleys. For a close-up view of the map where you can choose your zone, click here.

Now, that you've selected your city — or at least one in the same zone — input your square feet of landscaping, and you'll get your water budget in thousands of gallons. But what does that mean in terms of what you're growing?

That's where the Estimated Total Water Use calculation comes in. Click on the ETWU tab on the bottom of the page. Now, you can determine how much water your landscaping likely drinks, based on how thirsty your plants are. You can even look up which species of flowers, trees and shrubs are water hogs and which are sippers by clicking here to consult the "Water Use Classification of Landscape Species: A Guide to the Water Needs of Landscape Plants." It classifies species according to "high," "medium" or "low" water use.

To meet state regulations, the Estimated Total Water Use of a site must not exceed that site's Maximum Applied Water Allowance. Play around with these spreadsheets, and you'll get an idea of how your own yard compares to the water-sipping future that state regulators envision.

Happy water budgeting!

Listen to the Wither The Lawn radio report online.

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Katharine Mieszkowski

About the Author ()

Katharine Mieszkowski is a Bay Area environmental reporter. She grew ),(up in a suburb of Houston, where there's still no curbside recycling. ),(A graduate of Yale, she's been a staff writer for Salon and Fast ),(Company. On the green beat, she's covered everything from ),(Yellowstone's grizzly bears to Wal-Mart, gray water to plastic bags. ),(Her work has also appeared in the New York Times, Rolling Stone, ),(Mother Jones and on All Things Considered. She lives in Kensington, where there is curbside recycling, but no food-waste program yet.