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Irrigation-Soil-roots-Conservation Corner your plants, use a soil probe. Photo: Karolina Grabowska/Pexels soil probe tips

Soil Probe Tips for Success

February 11, 2021/in Conservation Corner, Features /by Gayle Falkenthal

Knowing how to use a soil probe as an important soil management tool will support your effort to create a healthy, thriving landscape full of beautiful plants.

You need to first know as much as possible about your soil to understand your irrigation needs. Irrigation is critical to keep your landscaping green and growing. But more isn’t better. One way to easily gauge your landscape’s needs is to use the Jar Test.

Another helpful tool is a soil probe. A soil probe lets you determine a lot more information about the soils in your landscaping. It will give you information about whether your irrigation is successfully reaching the roots of your plants, or even if it soaks in too deep past the reach of plant roots.

If you don’t understand your individual soil profile, you can’t plan effective irrigation. When there is variability in the conditions across your landscape, you may have different types of soils from one area to another or from a surface layer of soil to a deeper layer.

A good soil probe will help you figure out when your irrigation water has reached the right depth for the plants in your landscaping. It is a simple process with the right tools.

How to use your soil probe

Use a soil probe to test how well irrigation dispenses into your landscape. Photo: Courtesy University of Florida/Creative Commons soil probe tips

Use a soil probe to test how well irrigation dispenses into your landscape. Photo: University of Florida/Creative Commons

When your soil is moist, a soil probe should go into the ground easily, without a lot of effort. Your soil probe will stop when it hits hard, dry dirt, and won’t go further. But your soil probe could also be hitting rock, so you may want to reposition it just a few inches away and try again.

If you are confident you’ve hit only dry soil, put your fingers around the probe at the soil surface, and pull it out. Measure the depth in inches to learn how deep your irrigation will penetrate into the soil.

To properly irrigate your plants, understand the depth of their roots. Trees send their roots much deeper into the soil than shrubs, and shrubs have deeper roots than bedding plants like annual and perennial flowers or vegetables.

Most plants will do fine as long as the top foot of soil (12 inches) is filled with water when you irrigate. Shrubs should be irrigated to a depth of two feet (24 inches), and trees irrigated to a depth of three feet (36 inches).

You can purchase a soil probe at any general hardware store or gardening center. A basic soil probe costs between $30 and $80, but there are high-tech probes costing up to $300.

To learn more about your soil, sign up for Soil & Site Assessments virtual workshop.

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

Scholarship applicationsvfor 2022 are now available. Water industry education

Scholarship Applications Open for Aspiring Water Pros

February 8, 2021/in Education, Features, Jobs and Training /by Gayle Falkenthal

If you’re a student considering college studies leading to a career in the water and wastewater industry, several California water associations and San Diego regional member water agencies offer college scholarships.

Scholarships are available for community college, college, and graduate-level programs. Here are a few of the funding opportunities for study in the 2021-2022 academic school year.

Statewide water scholarships

Approximately 1,400 water and waster industry jobs will become available in San Diego County in the next five years. Photo: Water Authority scholarship application

Approximately 1,400 water and waster industry jobs will become available in San Diego County in the next five years. Photo: San Diego County Water Authority

The Water Environment Federation’s Canham Graduate Studies scholarship provides $25,000 for a post-baccalaureate student in the water environment field. The scholarship is for education-related expenses such as room and board, tuition, and books. The scholarship may not be used to cover stipends or wages.

The applicant must be a WEF member, complete an online application, and be enrolled in a graduate program. Recipients must commit to working in the water industry for two years following graduation.

Deadline: March 1, 2021. WEF Scholarship Application Link

The California Water Environment Association is offering $30,000 in scholarships this year to students pursuing a career in the clean water profession. The deadline to apply for the CWEA Kirt Brooks Scholarship program is Feb. 15.

The Association of California Water Agencies offers a $3,500 scholarship to qualified applicants attending a University of California or California State University school pursuing an undergraduate degree in a water-resources related field such as engineering, agriculture, environmental studies, or public administration. The applicant must be a junior or senior attending full-time during the 2021-2022 school year. Criteria include scholastic achievement and motivation to the vocation of water-resources management.

Deadline: March 1, 2021. ACWA UC and CSU Scholarships Application Link

The California-Nevada section of the American Water Works Association awards more than $20,000 in scholarships supporting students and professionals pursuing careers in a drinking water-related field. Two $5,000 graduate scholarships and four $2,500 undergraduate scholarships are available. Two additional $1,000 scholarships fund training as a drinking water treatment/distribution operator in trade or community college programs.

Suitable candidates include environmental and civil engineers; water, wastewater, and recycling treatment plant operators; distribution system operators; chemists; laboratory technicians; biologists, ecologists, and environmental scientists; and others whose roles support safe and reliable drinking water.

Deadline: March 15, 2021 AWWA Scholarship Application Link

Eight local scholarships are available from two member water agencies for students in the North County and East County. Photo: Water Authority

Up to eight local scholarships are available from two member water agencies for students in the North County and East County. Photo: San Diego County Water Authority

San Diego regional water scholarships

The Helix Water District offers two $1,000 scholarships to graduating high school seniors who will begin their university studies next fall. Applications are due April 1 for the Dr. Lillian M. Childs Scholarship and the Robert D. Friedgen Scholarship, which provide help with freshman year expenses. The scholarship committee reviews each applicant’s grades, extracurricular activities, volunteer and work experience, academic and career goals, and financial need.

High school seniors must graduate in Spring 2021 and attend a four-year college or university next fall. Applicants must live in Helix’s service area, including the cities of Lemon Grove, La Mesa, and El Cajon, the community of Spring Valley, and unincorporated areas of the county.

Deadline: April 1, 2021. Helix Water District High School Students Scholarship Application Link

The Vista Irrigation District offers up to six scholarships to high school students living or attending school within the district. Awards range from $1,000 to $3,000. The purpose of the scholarship program is to encourage students to learn more about water-related issues impacting their community. Students who compete for a scholarship must complete an essay and provide a personal statement related to their background and/or goals. Selection criteria also include community involvement or volunteer service and letters of recommendation from high school faculty.

Deadline: April 5, 2021. Vista Irrigation District High School Students Scholarship Application Link .

The San Diego County Water Authority and its 24 member agencies have created a regional workforce development task force to address the ‘Silver Tsunami’ of experienced employees reaching retirement age. With approximately 1,400 water and wastewater jobs expected to open up across San Diego County in the next five years due to retirements, water industry careers offer promising lifelong professional opportunities. For more information, visit sandiegowaterworks.org

Set yourself up for landscaping success by building the best foundation in your soil structure. Photo: walkersalmanac/Pixabay healthy soil

Oxygen, Water, and Life Create Healthy Landscape Soil

February 4, 2021/in Conservation Corner, Features /by Gayle Falkenthal

Your landscaping soil needs three things to feed the billions of microbes within it to transform brick-hard, lifeless dirt into healthy, living soil sponges: oxygen, water, and life. Think OWL to remember these important, interconnected factors.

Oxygen lets microbes breathe free

Oxygen is needed by healthy plant roots and soil organisms. Healthy soil has lots of tiny little pockets of air. When soils are eroded, graded, or disturbed, their structure becomes compacted and hard. Compaction takes place when tiny air and water bubbles are squeezed out of the soil. This kills the healthy microbes working to keep your soil replenished. Microbes can be killed by fertilizers, pesticides, or even heavy traffic from people or vehicles.

Water for your microbes and plants

Microbes and plans both need water to live. But too much water in your soil will displace oxygen, saturating the soil. This creates an anaerobic condition. It is the unhealthy microbes like bacteria, viruses, or parasites that prefer anaerobic soil. If this condition persists, diseases may develop. They will endanger the health of your garden.

Water is constantly moving through the soil. Water in the soil needs to be replenished as plants use it, as it evaporates from the soil surface, and as gravity pulls it down past the root zone of your plants.

Bring your soil to life

The microbes consume organic matter, and then they are consumed by bigger creatures (worms, ants, slugs, centipedes, larvae, etc.). They are consumed in turn by creatures further up nature’s food chain. Photo: Malcolm Fowles, Wikipedia

Life in the soil includes all the bacteria, protozoa, nematodes, and fungi, the food they eat, the excretions they make, and the root systems they sustain. Living microbes are most quickly incorporated into your soil by adding high-quality compost.

Plants attract microbes to their roots by feeding them carbon. Bacteria and fungi hold the soil together with microscopic glues and binders. The microbes consume organic matter, and then they are consumed by bigger creatures (worms, ants, slugs, centipedes, larvae, etc.). They are consumed in turn by creatures further up nature’s food chain.

Carbon and other nutrients cycle through these many life forms, creating healthy living soil, no matter what the soil type.

Without any of these elements, your landscaping will not thrive. Organic matter, planning and some labor may be involved, but creating healthy soil using the OWL method – Oxygen, Water and Life – will pay off in reduced maintenance, reduced inputs, reduced pollution on land and in our waterways, and the beauty of your thriving, healthy landscape.

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

City of Escondido Wastewater Treatment Plant Operator Carrie Selby is among a growing number of women working in water and wastewater industry careers. Photo: City of Escondido

Women in Water Symposium

February 1, 2021/in Education, Features, Jobs and Training /by Gayle Falkenthal

The fourth annual Women in Water Symposium in March will be online this year due to the coronavirus pandemic. Previously hosted at Cuyamaca College, symposium sessions will be each Thursday starting March 2. This year’s conference theme is “Flow With The Change.”

Three specific career level tracks are offered to address needs at each level: entry-level for those new to water careers; mid-career for those transitioning and advancing within the industry; and upper level, for senior professionals looking to leave a legacy.

Session topics include negotiation skills; diversity, equity, and inclusion; dealing with change; the impact of COVID-19; and building a sustainable career. Program elements for all tracks are designed to create a larger community of people with the interest and aptitude to take on what were previously considered non-traditional careers.

The symposium is an opportunity for students, water industry professionals, and people exploring careers in the water and wastewater industry, to make connections.

“The Women in Water Symposium made it possible for me, as a young graduate student, to meet experienced, female engineers at any moment, from breakfast to sessions and everything in between,” said Alma Rocha, a San Diego State University graduate student studying environmental engineering.

“I got to meet so many amazing people and help them out with referrals to jobs and events that might help their career, ” said Alec Mackie with the California Water Environmental Association. “A very rewarding event.”

Vanessa Murrell, Foundation for Grossmont and Cuyamaca Colleges grant manager, said the conference is open to anyone, and this year is not limited by location by being held in a virtual environment.

Nurturing the next generation of water professionals

Water Authority General Manager Sandra Kerl is a longtime supporter and speaker at the Women in Water Symposium series at Cuyamaca College. Photo: Cuyamaca College

Water Authority General Manager Sandra Kerl is a longtime supporter and speaker at the Women in Water Symposium series sponsored by Cuyamaca College. This year’s symposium will take place online. Photo: Cuyamaca College

The Water Authority and its 24 member agencies have created a regional workforce development task force to address the “Silver Tsunami” of experienced employees reaching retirement age. The task force reports approximately 4,500 water and wastewater positions in the San Diego region. More than 1,400 of those workers are expected to reach retirement age by 2024. Water and wastewater treatment plant operators in California earn an annual average wage of more than $72,000, according to the U.S. Bureau of Labor Statistics.

Registration is $25 and free to students. Attendees only need to register once for all symposium sessions. Participants can attend any session from all three tracks. Register here.

Improve Your Landscaping Soil With a Soil Test

January 28, 2021/in Conservation Corner, Features /by Gayle Falkenthal

One of the first steps in your landscape makeover project involves preparing the soil to allow efficient use of irrigation. San Diego County soil quality needs a lot of help. The area is defined by impermeable soils with poor infiltration areas. Water doesn’t flow through the soil to replenish the groundwater, because it is made primarily of clay which is too dense.

In impermeable soils, irrigation doesn’t soak evenly into the ground, or flow through living soil and plants in a healthy way. No matter where you do your landscaping, you need to put in some work to improve your soil structure as much as possible. Irrigation will be more efficient and more cost-effective, and your landscape plants will receive the nutrients and water they need to flourish.

Check for particle size

Before you can build better soil, you need to figure out what type of soil you are working with. The three basic types of soil are:

Clay: Soil made up of the smallest particles
Silt: Soil made up of a mixture of particle sizes
Sand: Soil made up of the largest particles

In general, sandy soil drains faster than clay soil, because there is more space among the larger sized particles. Soil structure also influences soil quality. Lifeless, compacted sandy soil will not absorb water, while healthy clay soil will be more sponge-like, holding and releasing water when needed.

Learn your soil type using the jar test

Some tests can be done onsite to figure out what kind of soil you have. Others require lab analysis. Certain conditions require specialized tests, such as soil used for food production or soil receiving a lot of stormwater.

For most landscaping projects, you can test your home landscaping soil yourself. Watch the video, then follow these directions for a “Jar Test.” This is a fun science project to do with kids.

Use a one-quart size glass container.
Add one cup of soil from the garden. You can select one area or take samples from several areas and blend them together.
Add three cups of distilled water.
Close the jar and shake it until all the soil solids are suspended in water.
Put the jar on a shelf and wait 24 hours.
If the container is still cloudy, wait another 24 hours.
After 48 hours, the soil layers should be settled on the bottom.
Measure the layers in proportion to each other, with the total adding up to 100 percent.
Sand will be on the bottom, silt in the middle, and clay on top.

Refer to the graphic to determine your soil type, based on the proportions of sand, silt, and clay.

Compare your soil to these diagrams to determine your landscaping’s soil composition. You can then adjust amendments to reach the optimum mix. Illustration: San Diego County Water Authority

Which jar does your home sample look most like? You will be able to work with your soil type to improve its condition, providing the best possible foundation for your landscaping plants and the most efficient irrigation.

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

National University's new four-year degree program will help water and wastewater employees advance in their careers. Photo: John Chacon, California Department of Water Resources John Chacon / California Department of Water Resources,

New Regional Degree Program Responds to Water and Wastewater Workforce Needs

January 26, 2021/in Education, Features, Jobs and Training /by Gayle Falkenthal

Driven by the rapidly growing demands for skilled career professionals in the water and wastewater industry, National University and Cuyamaca College will launch a new degree pathway program starting in February 2021.

Developed in collaboration with regional employers, the new Bachelor of Public Administration degree with a concentration in Waterworks Management provides a seamless pathway for graduates of the Cuyamaca College Center for Water Studies to transfer into the bachelor’s program after earning their associate’s degree. Transfers are also available to graduates of other community colleges.

“Responding to regional workforce needs, National University and Cuyamaca College are excited to roll out the Waterworks Management academic pathway, informed by industry leaders,” said Dr. Sara Kelly, academic program director at National University. Transfer scholarships are available for qualifying students.

Transfer program reduces completion time, cost

The new degree program will build capacity to train the waste and wastewater workforce of the future. Photo: John Chacon, California Department of Water Resources

The new collaboration allows students to complete both an associate’s and a bachelor’s degree while reducing the time and cost. Student support services at both institutions help foster a seamless process for students to transfer from Cuyamaca College to National University.

“Working collaboratively with National University, we can help our region and state respond to the need for skilled and educated water and wastewater professionals,” said Cuyamaca College President Julianna Barnes. “We know that with impending retirements in the industry, there will be a need for 12,000 to 20,000 water and wastewater professionals throughout the state in coming years.”

As current seasoned leaders retire, water and wastewater agencies struggle to fill job vacancies requiring a focused bachelor’s degree. Students earning the new degree will complete National University’s four-course concentration of upper-division courses studying water and waterworks management and leadership, water law and compliance, and human resources and labor law.

Graduates will be able to address the issues and challenges facing water and wastewater agencies at the state, regional, and local levels, including governing requirements and regulatory compliance while employing water management best practices.

Courses taught by water industry professionals

The new collaboration between National University and Cuyamaca College also welcomes Cuyamaca alumni into the program. Photo: California Department of Water Resources

Dr. Joseph Allen, Director of Community College Pathways at National University, said the curriculum was constructed based on the insight and recommendation of regional employers, coordinated by Cuyamaca College and the San Diego County Water Authority.

“There was a need for highly trained leadership in this industry,” said Allen. “This program provides a bachelor’s solution to train the management and leadership in the specific leadership areas needed in addition to the Associate’s degree in this field. Cuyamaca College has a solid program for the technical side and the frontline workers. Our new program is the next step in preparing the leaders of tomorrow for waterworks management.”

The program took more than a year to develop. Qualified water industry professionals from the Water Authority, regional member agencies, and consulting experts will teach courses.

“There is phenomenal talent in connection with this program, from around the world and not just San Diego,” said Kelly.

Cuyamaca College’s innovative Center for Water Studies program is the oldest and most comprehensive of its kind in the California community college system. It prepares students for careers at water agencies as technicians, mechanics, electricians, engineers, plant operators, information technology specialists, and more. Program alumni are eligible for the National University program.

Degree program launches in February 2021

National University offers all courses online, starting with the first cohort of students in the program in February 2021. Administrators plan to eventually offer onsite and hybrid courses involving the Cuyamaca College Center for Water Studies field operations skills yard for hands-on experience.

As a veteran-founded, private nonprofit institution, National University is dedicated to serving service members, veterans, and their families. This new BPA waterworks concentration is particularly well suited for veterans using their GI benefits to further their education. Veterans are eligible to apply their military experience and education toward certifications in the water industry.

“There are so many different pathways in life,” said Allen. “Whether you’re 18, whether you’re older. You’ve got family, children, and deployments. We’re going to put you on the right pathway to help you reach your final destination in your career.”

BPA program information is available on the National University website.

Mulching for Water-Use Efficiency

January 26, 2021/in Education, Features /by Kristiene Gong

Even though temperatures rarely drop below freezing in most parts of Southern California, many people overlook winter when it comes to caring for their native plants and traditional landscapes. There are many things that can help keep landscapes healthy and water-efficient, especially during the winter months when there is more natural rainfall. One of these things is to use a layer of mulch to prevent water loss and insulate landscapes during colder times.

Mulch types

For maximum sustainability and to support plant health, use a locally sourced and blended organic mulch. If the goal is to create a walking trail or other area that is not intended to grow plants, consider a longer lasting wood mulch or inorganic mulch. Organic mulch may be available at low cost from local landfill recycling centers. For optimum soil and plant health, look for a mulch that has a blend of leaves, stems and woody portions of the plants. This type of blended mulch will break down over time and add organic matter to the soil to support natural biological processes, prevent erosion, maintain soil moisture and support water infiltration into the landscape. In addition, composted blended mulch has gone through a natural maturation process that kills weed seeds and pathogens.

Mulching tips

Apply a layer of mulch three to four inches deep and remember to keep it at least four to six inches away from plant stems to avoid creating a condition that is prone to disease. In areas where the goal is to build the health of the soil, avoid using weed guard type fabrics. Pulling weeds and clearing debris also helps to increase the efficiency of mulch and removes hiding places for pests.

Reduce irrigation costs

With a layer of mulch on your landscape, you can conserve water because the layer of mulch will help keep moisture in the soil – this is especially important because most plants grow deeper roots in the fall and early winter. Be sure to also manage your irrigation by setting your irrigation schedule seasonally, controlling overspray and fixing any other problems promptly.

Winter Landscape Tip: Tell your landscaper about FREE training. Webinars in English and Spanish include sustainable landscape principles and irrigation essentials. Learn more: https://qwel.watersmartsd.org.

Qualified Water Efficient Landscaper training is made possible by the San Diego County Water Authority, its member agencies and the County of San Diego.

Want more tips for water-use efficiency and maintaining your sustainable landscapes? Check the free WaterSmart education classes and on-demand videos: WaterSmartSD.org.

Gary Croucher-Board Chair-San Diego County Water Authority-Primary

Water Authority’s Legal Efforts Protect Local and Regional Ratepayers

January 21, 2021/in Features, View From The Chair /by Mike Lee

I have some important news for our region to share: The San Francisco Superior Court has ruled the San Diego County Water Authority is the prevailing party in the agency’s first two lawsuits heard challenging rates and charges set by the Los Angeles-based Metropolitan
Water District of Southern California.

The order entitles the Water Authority to recover its attorneys’ fees and costs in those cases, in addition to a $44 million damage and interest awardmade earlier.

“San Diego prevailed, and the judgment not only benefits its own ratepayers but all of thenearly 19 million people in Metropolitan’s service area because enforcing cost-of-service principles serves the interests of all ratepayers,” said Superior Court Judge Anne-Christine Massullo in her Jan. 13 order, which can be appealed.

The exact amount of recoverable fees will be decided later. It is deeply gratifying that the court not only validated our claims but acknowledged the importance of protecting ratepayers by water agencies following the law.

The order makes it clear once and for all that our desire to protect San Diego ratepayers was never intended to harm MWD, its other member agencies or the ratepayers they serve. Rather, the litigation was necessary to address serious flaws in MWD’s rates that will, as the court said, ultimately benefit not only San Diego County ratepayers, but all Southern Californians.

This order is another major step toward achieving Water Authority board objectives and one of my key initiatives as Board Chair: to conclude the litigation and work together with other MWD member agencies to address MWD’s water resource and rate challenges. This is essential in order to ensure MWD’s fiscal sustainability—and that of its member agencies—now and in the future.

Click here to learn more about this issue.

WaterSmart homeowner Jeff Moore's back yard zen garden featuring his landscape work fit beautifully into his area's climate zone. Photo: Water Authority caring for

Match Your Climate Zone to Your Landscaping Plan

January 21, 2021/in Conservation Corner, Features /by Gayle Falkenthal

Making smart decisions about your landscape design and your plant choices relies in large part on your climate zone. San Diego County’s six different climate zones vary in their average conditions. By choosing wisely, you can minimize the need for artificial irrigation and still create a beautiful, sustainable landscape.

The California Irrigation Management Information System (CIMIS) divides San Diego County into these six climate zones: Coastal, Coastal Inland, Upland Central, Transition, Mountain, and Desert.

This climate system provides you factors to help you understand which plants will thrive in your landscaping under its native conditions. Gardening in harmony with your local climate zone and your microclimate helps you use resources, including water, most efficiently.

Descriptions of San Diego’s six climate zones

Which CIMIS climate zone are you in?

San Diego County’s geography falls within six of the 24 CIMIS climate zones. Photo: CIMIS

Zone 1: Coastal Prairie

The Coastal Prairie zone hugs our county’s coastline. It is the zone most strongly influenced by the ocean, with a mild marine climate resulting from the warm Pacific Ocean. Winters are mild, summers are cool, and there is almost always moisture in the air.

Zone 4: South Coast Inland

South Coastal Inland areas are just inland from the beach, or on high bluffs above the coastline. You can feel the ocean breeze, but you can’t taste the salt in the air. There is less fog and humidity than the immediate coastal area, and higher temperatures.

Zone 6: Upland Central

The higher elevation Upland Central areas are influenced both by moist coastal air and dry interior air. Humidity, morning fog, and wind are moderate, with low annual rainfall.

Zone 9: Transition

This marine-to-desert transition climate is farther inland. It features a combination of warmer thermal belts and cold-air basins and hilltops, with an occasional marine influence. The climate can vary from heavy fog to dry Santa Ana winds.

Zone 16: Mountain

Steep slopes, variation in sun and wind exposure, shallow soils and heavier rainfall affect plants in the Mountain regions. Average annual rainfall is 30 inches, and wet years can bring 45 inches or more.

Zone 18: Desert

Dry and hot daytime conditions combine with cold nighttime temperatures in the Desert zone. Humidity is very low, and water is scarce. Average annual rainfall can be as low as 2.5 inches, with an average of just 6 inches.

Learn more about the specifics of your climate and microclimate on the California Irrigation Management Information System website.

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

Fruit trees, especially citrus, thrive in San Diego County’s climates with just a little bit of care. The Pineapple Guava (Acca sellowiana) is a good choice with spectacular blooms. Photo: WIkimedia/Creative Commons License Edible Plants climate zone

Sustainable Gardeners, Get Into Your Climate Zone

January 14, 2021/in Conservation Corner, Features /by Gayle Falkenthal

People around the world know San Diego for its beautiful, sunny, and mild weather. San Diego residents know our daily weather has more variety than visitors might imagine.

Climate is defined as the average weather conditions in an area over a long period, generally 30 years or more. German climate scientist Wladimir Koppen first divided the world’s climate into six regions in the early 1900s.

Since then, U.S. climate zones have been defined in more detail. The U.S. Department of Agriculture defines climate zones according to the lowest average temperature in the region. You may also be familiar with the 24 climate zones identified in Sunset Magazine’s iconic Sunset Western Garden Book. The book is now out of print, but is available online as an interactive edition. Existing print copies from the last edition printed in 2012 are prized heirlooms.

Devoted gardeners still follow the 24 climate zones featured in the guide. This is based on the California Irrigation Management Information System (CIMIS) adoption of a similar map identifying 24 climate zones.

San Diego County’s geography falls within six of the 24 CIMIS climate zones. Photo: CIMIS

Evaporation + Transpiration = Evapotranspiration

Depending on the amount of rainfall, temperature, humidity, wind, shade, and the nature of the soil, water in the ground evaporates at different rates. When evaporation is higher, the soil becomes dry more quickly.

Evapotranspiration (ET) is the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces, and by transpiration from plants.

Reference Evapotranspiration (ETo) is a baseline formula. All your plant water needs are measured against this baseline in a complex series of measurements and calculations.

Why is understanding evapotranspiration important?

In metropolitan San Diego County, our annual ETo rate increases as you move inland, meaning the soil becomes dry more quickly.

Fortunately, we don’t need to worry about making these calculations on our own. CIMIS maintains a statewide system of weather stations and reference plots. From these, it has identified the six main ET Zones in San Diego County.

Understanding your ETo zone and gardening climate zone are important first steps toward deciding how much water your landscaping will need. Working against the ETo and gardening climate zones can greatly increase your need for irrigation.

Learn more about your ETo climate zone’s specifics and gardening microclimate on the California Irrigation Management Information System website.

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.

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