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How Much Water Can Your New Landscape Conserve?

Landscape designs using the least amount of potable water necessary are greatly encouraged in arid or Mediterranean climates like in San Diego County. It’s an important motivation for homeowners to consider efficiency and sustainability to lower water use, saving a precious resource.

An example of drought tolerant landscaping with low water use plants. Photo: Kelly M. Grow, California Department of Water Resources landscape conserve

How Much Water Can Your New Landscape Conserve?

Landscape designs using the least amount of potable water necessary are greatly encouraged in arid or Mediterranean climates like in San Diego County. It’s an important motivation for homeowners to consider efficiency and sustainability to lower water use, saving a precious resource.

Maximizing your landscaping’s ability to capture and use natural rainfall can also help reduce or even completely eliminate your reliance on potable water for irrigation.  Compare how much water your new landscape design will need against your existing landscaping’s water use. You’ll be able to estimate your future water savings.

Start by calculating the water use requirements of landscaping filled with plants that require high amounts of water, or moderate amounts, low or very low water requirements.

In these examples, evapotranspiration (ET), irrigation efficiency, and landscape area are exactly the same. The only difference: our examples are home to plants with different water requirements.

How to calculate your landscape’s water use

To calculate water use, you can refer to the San Diego Water Efficient Landscape Ordinance for guidance. Go to www.sdcounty.gov and search “Landscape Ordinance.” The four key variables are:

  1. Landscape Area (LA) – the square feet of area being landscaped with plants that require irrigation
  2. Evapotranspiration (ET) – this is the number in inches based on your San Diego Climate Zone
  3. Plant Factor (PF) – This is moderate, low, or very low depending on the plant selection
  4. Irrigation Efficiency (IE) – There is no such thing as a perfect irrigation system. Many factors can limit efficiency and impact your water use and the health of your plants.

Use a landscaped area of 1,000 square feet, with an ET of 51 inches annually, and IE of 0.7. Look at the big difference your plant selection can make in your water use.

Example 1: High Water Use plants (PF = 0.8) – 36,137 gallons of water per year

Example 2: Moderate Water Use plants (PF = 0.5) – 22, 586 gallons of water per year

Example 3: Low Water Use plants (PF = 0.2) – 9.034 gallons of water per year

Example 4: Very Low Water Use plants (PF = 0.1) – 4,517 gallons of water per year

From the highest estimate to the lowest estimate, you could potentially save 17,103 gallons of water every single year.

This article is part of a year-long series inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.

Drought Takes Hold in West After Second Dry Winter

Dry conditions in the Southwest, largely associated with La Niña, have intensified what the National Oceanic and Atmospheric Administration is calling the most significant U.S. spring drought since 2013, affecting an estimated 74 million people.

Opinion: The 2021 Drought is Already an Emergency

The 2021 drought is quickly becoming an emergency. Kern County’s supply from the State Water Project has been reduced to just 5 percent of a full allocation. Rainfall is about half of average. And with each passing dry day, the drought gets worse.

MCCSD Officially Declares Stage 3 Drought

The Mendocino City Community Services District board declared a Stage 3 drought at its latest meeting, March 29. The district has recorded approximately 20.5 inches of rain for the year to date; this is the second-lowest recorded total in the past 100 years.

A Stage 3 drought includes the following mandates:

  • 20% reduction in water usage of allotments
  • Designated irrigation times and an irrigation audit for landscape maintenance.
  • No vehicle washing except with a hand-held bucket or hose equipped with a positive shutoff nozzle
  • Prohibition on refilling of decorative fountains or ponds unless such water is part of a recycling system.
  • No refilling of hot tubs or swimming pools.
  • Drinking water served at restaurants only upon request
  • Recommended use of paper plates at restaurants to avoid dishwashing.
  • A temporary moratorium on new groundwater extraction permits for new development, expansion of existing use, and changes of use, which require a hydrological study.
  • Prohibitions on aquifer pump tests.

California’s Water Worries May Not Affect San Diego

California could be facing a dry summer after two dry winters, but there shouldn’t be a huge impact on local supplies.

California water officials have already cut in half the amount of water they expect to deliver from the state water project.

That could be a major cut for central valley farmers and other water users that rely heavily on the Sacramento Delta for their water.

Opinion: New Priorities Needed for California’s Next Drought

A series of key decisions await Gov. Gavin Newsom as the state heads back into a potential drought.

So this seems like the right moment to review what happened last time: Water was prioritized for big agriculture at the expense of the Sacramento-San Joaquin Delta, endangered species and California communities. The State Water Board, in a review of the drought of 2014-15, found operations “not sustainable.”

Know Your Plant Factor Water Requirements

Landscaping plants have different water needs. The water requirement of each plant in your landscaping can be determined by gathering information about the plant and then comparing it to the amount of water needed by the cool-season grass growing in your climate zone.

Knowing how to classify your plants by water use characteristics will help you plan your sustainable landscaping. Photo: Water Authority plant factor

Know Your Plant Factor Water Requirements

Landscaping plants have different water needs. The water requirement of each plant in your landscaping can be determined by gathering information about the plant and then comparing it to the amount of water needed by the cool-season grass growing in your climate zone.

Take a tip from landscaping professionals. They use a resource called the Water Use Classification of Landscape Species to classify plants according to their water requirements, called Plant Factors.

These water requirements divide plant species into four categories: Very Low, Low, Moderate, and High.

When you are selecting plants for your landscaping, use the classification to choose low water use plants for your landscaping. You can also use it to group a handful of higher water use plants together if you want to indulge in a few favorites.

When you have decided on your plant palette and placement, you can now figure out the water use of your entire landscape area. This will help you plan out your artificial irrigation.

Factor in watering requirements

Determine water use before choosing plants for your new sustainable landscaping. Photo: San Diego County Water Authority

Watering needs for landscape plants use a measuring stick based on cool-season turf. It’s because cool-season turf is extremely thirsty.

When you replace turf areas with climate-appropriate plants that use less water and irrigate them with more efficient systems, you can conserve a tremendous amount of water. You don’t need to turn your landscaping into a dry and dusty area to do it.

High Plant Factor: Plants needing 60 to 100 percent of the water needed for a grass lawn (PF of 0.6 – 1.)

Moderate Plant Factor: Plants needing 30 to 60 percent of the water needed for a grass lawn (PF of 0.3 – 0.6)

Low Plant Factor: Plants needing 10 to 30 percent of the water needed for a grass lawn (PF of 0.1 – 0.3)

Very Low Plant Factor: Plants needing 10 percent or less of the water needed for a grass lawn (PF of less than 0.1)

Irrigate More Efficiently By Grouping Plants

According to the San Diego County Water Authority’s Sustainable Landscaping guidebook, plant selections are colored-coded to identify their water needs under this system. It gives you an easy way to group plants by their water requirements in your new landscaping, so you can irrigate them more efficiently.

This article is part of a year-long series inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.

Welcome to the Board: Ismahan Abdullahi, City of San Diego

Ismahan Abdullahi was seated on the Board of Directors on January 25, 2021, representing the City of San Diego. Director Abdullahi serves on the Administrative and Finance and Engineering and Operations committees for the Water Authority.