Water Conservation Lessons From California

Decades of drought brought about MWELO, WUCOLS, and other acronyms. What do they mean and what can landscapers learn from them?

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By Dave Phelps
From the June 2023 Issue

Everybody’s talking about the wild climate extremes and the news out of California tells it all: the hottest days, most extended droughts, most devastating fires and mudflows, and even tornadoes in LA and “firenadoes” (or whirls) in the wildfires. Meteorological terms like atmospheric rivers and bomb cyclones are entering the common knowledge.

water conservation California
The most overarching effect [of the drought], besides more water metering and higher water rates, has been the adoption of the Model Water Efficient Landscape Ordinance or MWELO. (Photo: Adobe Stock / Montreehanlue)

While California politics may be contentious, nobody can argue with former Governor Brown’s declaration of the changing climate as “the new abnormal” or Governor Newsom calling it “a damn emergency.” Three of Newsom’s executive orders directly address the situation, affect the landscape industry, and are worth reading. EO-N-20 addresses the increasing loss of biodiversity, while EO-N10-21 and EO-N-3-23 address climate change and water conservation.

The challenge for landscapers, property managers, and ecological stewards to plan concurrently for too much water, not enough water, and fire—while also attempting to save and create habitat—has led to improved practices that directly affect the landscape and turf industries in California.

The challenge for landscapers, property managers, and ecological stewards to plan concurrently for too much water, not enough water, and fire—while also attempting to save and create habitat—has led to improved practices that directly affect the landscape and turf industries in California. These practices might be worth considering in other jurisdictions as well.

Model Water Efficient Landscape Ordinance (MWELO)

The most overarching effect, besides more water metering and higher water rates, has been the adoption of the Model Water Efficient Landscape Ordinance or MWELO. (For background on MWELO, see “Water Efficient Landscape Design”) This ordinance—unlike previous draconian water restrictions that seemed arbitrary, blunt, and had questionable efficacy—is a holistic approach that applies common sense to the issues at hand. Nor does it go away when there’s a season of decent rain.

At first glance, it appears to be only a water budget and a local climate-based program for landscape water use. A thorough read, along with the accompanying Guidebook, however, provides a wide and solid foundation that has resulted in MWELO’s inclusion in the California Green Building Standards Code. This means MWELO requirements are triggered at local building departments when permits, design reviews, or plan checks occur for projects that include any significant landscaping.

Complaints regarding MWELO have been many, mostly centered around its cost and complexity. As part of the Building Code, however, it gets updated every three years so it’s currently being simplified. Adoption was slow initially, but efforts of the Department of Water Resources (DWR) and the National Resource Defense Council (NRDC) have—in some cases through class action lawsuits—brought many municipalities and water agencies into compliance. In fact, many have opted to create their own ordinances exceeding state requirements.

Turf & Irrigation

When it comes to turf, there are several aspects of MWELO worth noting. One is the clear distinction between Recreational or “functional” and Non-Recreational, or purely aesthetic turf. When you look at traditional turf use in many California communities through the lens of MWELO, you quickly realize just how much turfgrass is currently inappropriate for the climate in which it’s planted. This is especially true of parking strips and street medians. Under MWELO’s 2015 rules, which still apply today:

  • Turfgrass is limited to 25% of all landscaped areas in newly constructed single family residential homes with more than 500 square feet of landscaped area.
  • Renovations to existing outdoor areas with more than 2,500 square feet of landscaping must also comply with these regulations.
  • Non-Recreational grass is effectively banned in landscapes of new commercial, industrial, and institutional buildings. In multi-family settings it is only allowed in areas dedicated for community recreation.

Another key factor of MWELO is the acknowledgment that overhead or spray irrigation causes run-off when applied in areas that are too narrow, too close to hardscapes, or on steeper slopes. The current version disallows overhead irrigation on areas less than 10’ wide, within 2’ of a hardscape where the water doesn’t drain back into the landscape area, and on slopes exceeding 25%. In addition to this, requirements for proper pressure regulation, matched precipitation rates, and low-head check valves are baked into the ordinance. Application rates are also limited to eliminate run-off and weather or soil moisture-based controllers. Rain shut-off devices are also mandatory. So are swing joints on pop-up bodies, metering, manual shut-off valves, manifold isolation valves, and in many cases, flow sensors.

These overhead spray restrictions, along with the water budgets, and the necessity of the turf area(s) to be Recreational, or functional, in nature on non-single family residential lots, have had a huge impact on current landscapes. “Special” landscape area designations also promote edible landscaping, reclaimed water use, rainwater capture and use, and even greywater systems.

Stormwater

The Storm Water Pollution Prevention Plan (SWPPP) along with Low Impact Development (LID) requirements work hand in hand with MWELO to promote the disconnection of hardscapes and downspouts with storm drains and instead create rain gardens, vegetated swales, and infiltration areas.

At the same time, the effort to eliminate run-off, or reduce it to the maximum extent practicable (MEP), has been applied to stormwater as well. The Storm Water Pollution Prevention Plan (SWPPP) along with Low Impact Development (LID) requirements work hand in hand with MWELO to promote the disconnection of hardscapes and downspouts with storm drains and instead create rain gardens, vegetated swales, and infiltration areas.

This confluence of ordinances also has incentives for increased use of large landscape trees with the necessary soil volumes to ensure their health and longevity. The ability of the landscape to sequester carbon, slow down, filter, and reduce stormwater, as well as recharge local aquifers, is coupled with requirements to maximize the efficient use of potable water.

Beyond Water

MWELO goes beyond the efficient use of water in the landscape. One of the most important aspects is its focus on soil, mulch, and creating friable soils conducive to healthy root growth. While allowing for what is best for specific plants, it mandates a minimum amount of soil organic matter for most landscapes. It also includes minimum mulch requirements and promotes sheet mulching, while equally encouraging some non-mulched areas for native bee habitats. It also discourages the use of invasive plants.

Local fire marshals have also changed the landscape paradigm by reducing the use of pyrophytic plants (those that co-evolved with periodic fire events and thrive with frequent low-temperature fires), promoting defensible space zones, and even implementing no-plant zones around structures in some municipalities.

To add to the benefits of ordinances promoting healthy soils, irrigation efficiency, and stormwater plant filtration—along with carbon sequestration and fire safety—many agencies and municipalities have added significant financial rebates to achieve compliance. While the situation has been a dramatic wake-up call, and a financial burden to property owners, the rebates are driving a paradigm shift.

The old “mow, blow, and go” has been replaced with ecological management, regenerative practices, and increasing biodiversity and eco-services.

In the past, vast stretches of immaculate, verdant turf were an image of prosperity and affluence. However, it’s quickly becoming a sign of being out of touch and ecologically irresponsible. The old “mow, blow, and go” has been replaced with ecological management, regenerative practices, and increasing biodiversity and eco-services.

The knowledge base necessary to deal with an exponentially growing plant palette, soil ecology, natural plant pruning and maintenance, and the latest advances in irrigation technologies, are raising the bar of the landscape industry. The new paradigm requires a whole new level of acumen, of knowledge, and of skill. Yes, it’s certainly more complicated, but the compensation is also higher and the demand for this higher skill level is growing.

Landscape Triage

Enter the concept of Landscape Triage. In California, it’s the starting point of the transition to MWELO compliance. In any area, it adds real societal and ecological benefits for long-term landscape resilience given the rapidly increasing climate extremes and the biodiversity crisis. To understand the concept, consider this scenario playing out across California and any area facing water shortages.

How does a Board of Directors or Landscape Committee use their limited resources to best address what is, in many cases, a dramatic shift in landscape expectations? What are the low-hanging fruit they can afford in the near term? What are the phases they can budget for to come into compliance; to project a confident, proactive, and ecologically responsible stance; and to assure users of the space/stakeholders that “they got this?” If you can answer these questions for them, you’re bringing real value to the table.

The answer is multi-faceted, but fairly simple: Look at their turf. First, determine where are the larger, most level, and centrally located areas that could be considered “recreational” or “functional?” Define those areas and re-design the irrigation to maximize its efficiency. This usually means swapping out old spray nozzles with low-volume rotating mini-rotors on pressure-regulating pop-up bodies or fine-tuning the nozzles on rotors.

Then, address areas of turf less than 10’ wide. Maximize local rebates and implement sheet mulching and a spray-to-drip transition using “climate-appropriate” plants with Low WUCOLS values (see below). Next, swap out the old controllers with “smart” controllers that reprogram the irrigation schedule every day given historically averaged evapotranspiration curves modified by current weather data and overridden with rain shut-off devices.

Trees, if practicable, should be placed on their own hydrozone, a valve or valves able to be operated independently in dire situations to maintain a tree’s health and special needs—such as infrequent deep soaking to promote a deeper root zone. The financial, social, and ecological value of mature trees offsets conservation guidelines that may apply to shrubs or perennials during drought.

Water Use Classification of Landscape Species (WUCOLS)

Naturally, the knowledge necessary to make this transition is not insubstantial. This is where the Water Use Classification of Landscape Species (WUCOLS) database is brilliant. It defines plant water needs by climate zone, species, and even cultivar. It was devised and updated by UC Davis and the California Center for Urban Horticulture (CCUH) and is now required by MWELO.

WUCOLS provides the irrigation needs for over 3,500 plant groups used in California landscapes based on extensive field experience of horticulture experts. Essentially, it provides guidance in the selection/care of plants relative to their water needs. For California landscapers, the WUCOLS database allows creation of “favorite” plant lists by water needs for climatic region. While zones are specific to California, similar climates can benefit from the data.

The WUCOLS water use designations are used in the Estimated Total Water Use (ETWU) calculations required by the performance approach to the MWELO (yes, there’s math involved). The landscape designer must show the ETWU is less than the MAWA (Maximum Applied Water Allowance). This is game-changing.

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While one could easily argue that all these ordinances and regulations are too onerous, too expensive, and an infringement on property owners’ rights, one could also look at the “new abnormal” and “damn emergency” we find ourselves in. A confluence of common sense, science-based, watershed, climate specific, and plant-based ordinances incorporated into building permit processes is much more effective long term than a “you can only irrigate Tuesdays and Thursdays” restriction implemented largely when it’s too late.

I like to refer to landscapers as “first responders.” Not to deflate the importance of police, fire, etc., but rather to impart the significance and responsibility of those who design, install, and maintain our lands. The landscape is an imperative part of our experience and a driver of societal well-being. This era of increasing climate extremes demands our best effort right now. It’s necessary to transition our landscapes with regenerative strategies in alignment with science. It’s time to raise the bar. The climate issues we see in California are only the beginning of what will be a multi-generational struggle worldwide. Let’s take these lessons to heart and promote them to other areas that can benefit from the California experience.

water conservation CaliforniaPhelps is a landscape architect in California. He has been a landscape contractor, certified arborist, Master Gardener, and water-efficient landscaper, and has taught a wide range of landscape topics for CLCA, ReScape, CNPS, UC Master Gardeners, etc. His company, Garden Enlightenment, currently specializes in MWELO compliance and regenerative landscape practices and has online courses on Soils, Sheet Mulching, Pruning, and Irrigation. 

Do you have a comment? Share your thoughts in the Comments section below, or send an e-mail to the Editor at cmenapace@groupc.com.