02.06.12Ben Green

Landscape Water Volume & Cost: A Guess at Best

Rob Maday, Founder, Landscape Resource Amount of water used by housing irrigation

In Richard Restuccia’s post last year, Inspect What You Expect, he touched on the importance of seeing results as an instigator of change. Rob Maday, founder of, is of the same thinking and takes the measure what you manage philosophy to the next level with water consumption, by encouraging consumers to understand the difference in water consumption for landscape versus other uses. Rob agreed to share his thoughts and advice as a guest blogger in his post below. Make sure to also visit his webpage to check out the Water Calculator tool he developed, which takes your zip code and tells you all kinds of useful information regarding water usage.  This is not some crazy technical website, it is very practical and I think is an amazing resource.  I like his holistic approach to water management because he focuses on exactly what your climate says about being water wise.


Here’s a worrisome thought:  The vast majority of homeowners have no idea what proportion of potable water flowing into their property is used inside versus outside the home.  That means millions of households with landscapes pay a water bill each month with the limited understanding that in summer months they pay more and winter months a touch less.  Without knowledge of the distinction between water used in the landscape and water used inside (bathrooms, kitchens, laundry, etc.), it is impossible to clearly communicate the gravity of the Western states water crisis.

When gas prices reach upwards of $4.00/gallon, people take note and adjust their lifestyles accordingly.  But how will we ever make the giant strides necessary to preserve a dwindling resource when there is no clear dollar sign affixed to irrigation water in our water bills?

Current water conservation efforts are all well intentioned and are actually effecting change…but not to the degree needed.  I posit that until all households have a water metering setup that can differentiate between the two uses, the most powerful instigator of change, money, cannot effectively work to the water conservation movement’s advantage.

Without any wide-reaching proposals on the horizon for such legislation, we are left with a number of ways to “estimate” how much water our landscapes drink.  Beyond the general percentages that are tossed around (30-40% of water bill goes to landscape) I’ll highlight three of the most popular methods of estimating water usage and costs:

1.  Landscape Coefficient Method: The most notable, and most widely used, is the Landscape Coefficient Method(Disclaimer:  To understand and utilize this method, you’ll need to invest some time.) The landscape coefficient is a detailed formula that incorporates a variety of site conditions including Evapotranspiration, plant density, spacing, specific landscape species water needs, microclimate, and more.

Landscape Evapotranspiration = Landscape Coefficient x Reference Evapotranspiration

This method works well for new or large projects or for professional planning purposes, but to the average homeowner looking for a quick answer, it is a non-starter.

2.  Site Observation: Or, for existing landscapes, one can use the time-tested method of site observation; count the irrigation heads and drip emitters, note all of their flows, add up their totals, note which circuit they are on, multiply the run times by the flows, then do some basic math conversions.  This process is a tad time consuming and leaves room for assumptions that can produce inaccuracies, but is nonetheless another viable option.

3.  Online Calculators: If the above methods don’t apply to your situation, Google “water usage calculators” and you’ll find a variety of online resources that aim to estimate your water needs.  There is a whole spectrum of calculators from dizzyingly complex to downright basic which satisfies a diverse number of users.  One such simple calculator, provided on Landscape Resource, simply prompts the user to select their location, enter a square footage, then hit calculate.  The results are derived from the Landscape Coefficient Method and compare a water-wise plant scheme to a cool season turf grass in order to illustrate the potential savings in gallons and cents.

Although somewhat limited, the above three methods for estimating water usage are currently some of the best and most available tools in the landscape industry.  Hopefully, more effective ways of communicating the cost of irrigation water to the public will become more available and standard practice in the near future.  In the interim, landscape professionals are in a position to design and install systems that include dedicated irrigation meters, in addition to their palette of standard water saving devices, aimed at giving homeowners the tools and resources needed to make appropriate landscape decisions.

Rob Maday, ASLA, graduated with honors from Cal Poly State University, San Luis Obispo, with a degree in Landscape Architecture and a desire to create landscapes in keeping with California’s climate and culture.  In addition to his private landscape architecture practice (RMLA), Maday created, developed and administers an online resource:   The mission of the website is to improve California’s landscape by promoting sustainable and progressive landscape choices.

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Ben Green

Ben Green is our walking encyclopedia for irrigation systems, technology and materials. From basic to complex, Ben has installed irrigation systems of all types for a variety of properties. For almost 10 years now, Ben has developed from a ValleyCrest intern to become our go-to project manager for large complex landscape installations. Ben’s interest lies in the science and technology behind the tools and systems that enable best water management practices.




  1. Wednesday, 8:10 Randy Barron

    We make it a tad more simple for our water customers, Ben. Our sewer usage fees are predicated on average winter water usage. This sewer cap is indicated on the customers bill, along with the 4 increasingly pricey tiers of water rates. The four tiers are up to sewer cap, sewer cap + 8kgal, sewer cap +30kgal and above 30kgal. This pricing structure lets the customers know how they are doing on their landscape water use. It’s not as ideal as our dedicated irrigation billing (which is based on landscape square footage and current ETo), but it gives a good snapshot.

  2. Monday, 10:03 Ben Green

    Hello Randy,

    I had no idea that type of information is available on your water bill. I am assuming each water district has something similar or is this very unique to your city? Which City do you represent?

    Thanks again, i am going to take a look at my bill right now.


  3. Monday, 11:10 Randy Barron

    City of Santa Rosa, CA, Ben. The monthly bill includes the sewer cap, usage in each tier, and a bar chart comparison to last year’s monthly use. For our dedicated irrigation customers, we can provide a water use analysis that includes a multi-year breakdown of usage per tier, amount over/under budget, and the $ amount that could have been saved irrigating to budget. This is an excel sheet with charts that is provided at each audit, and on request from the customer. We also arrange for the customers to sign a release allowing us to update these analyzers for their landscape contractors (Lets them see how they’re doing and where to improve). It’s also an excellent ‘estimate’ of landscape water use 🙂

  4. Monday, 11:20 Ben Green

    Thank you for the reply, I am going to see if my city has something similar.

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