What is AB 1881?
California Assembly Bill 1881 is the Model Water Efficient Landscape Ordinance (MWELO) and it goes into effect Jan. 1st, 2010.


What's in it and why do I care?
If you (or your office) produce planting and or irrigation plans, AB 1881 has specific details and provisions as to applicability and content of those plans.

Some of the provisions are:

  • minimize over spray and runoff
  • landscape water budgets
  • landscape design by "hydrozone" (groupings of plants by water usage)
  • ET controllers and creation of base schedules
  • provide soil assessment and soil management plans
  • provide landscape maintenance plans
  • provide landscape maintenance practices
  • encourage the capture and retention of storm water onsite
  • encourage the use of recycled water
  • encourage use of economic incentives
  • educate water users

.new construction and rehabilitated landscapes which are developer-installed, homeowner-provided and/or homeowner-hired landscaping in single-family and multi-family residential projects with a landscape area equal to and greater than 2,500 square feet requiring a permit, plan check or design review.

Effective Jan1 st, 2010 all local agencies shall adopt the Model Ordinance, or one that is at least as effective (i.e. "stringent"..our word..) as the Model Ordinance in conserving water.

Like this newsletter? Sign up for our monthly newsletters

"A local agency may establish and administer penalties to the project applicant for noncompliance with the ordinance to the extent permitted by law."

Some Elements of the Landscape Documentation Package.
(A long...long... list of requirements that we will only just touch on here....)

Each irrigation plan shall have a Hydrozone Informational Table that includes:

  • controller number (controller "A", "B" etc..)
  • valve circuit number (that corresponds to the hydrozone number from the Planting Plan)
  • plant type (low, medium, high water use as defined in WUCOLS)
  • irrigation method (drip, spray, etc..)
  • area in square feet
  • % of landscape area

Some other notable items from the Model Ordinance...

The Maximum Applied Water Allowance will set the (maximum) amount of water you will be allowed to use on the landscape. Oh and by the way, we now have to use an ET Adjustment factor of .7 !

Example: If your annual ET is 45, its adjusted down to 31.5 Are you thirsty yet?

...but..if you have a Special Landscape Area (SLA), you can use your established ET factor . (Interestingly enough, the terminology for this is: "ETAF for Special Landscape Areas shall not exceed 1.0)

(An SLA is an area of the landscape dedicated to edible plants, areas irrigated with recycled water, water features using recycled water and areas dedicated to active play such as parks, sports fields, golf course, and where turf provides a playing surface...suggestion..start growing tomatoes.)

Irrigation Efficiency
For the purpose of determining the Maximum Applied Water Allowance (MAWA), irrigation efficiency is assumed to be 0.71. Irrigation systems shall be designed, maintained and managed to meet or exceed 0.71 efficiency. (many spray nozzles are considered to have an irrigation efficient less than 71%...which means they cannot be used!)

native parkway plantingOverhead Irrigation
Narrow or irregularly shaped areas less than eight (8) feet in width in any direction shall be irrigated with sub-surface or low volume irrigation technology. ..and ..Overhead Irrigation shall not be permitted within 24 inches (it is, or was 18" in Santa Monica...) of any non-permeable surface.

Allowable irrigation within the setback from non-permeable surfaces may include drip, or other low flow non-spray technology. The setback area may be planted or unplanted. The surfacing of the setback may be mulch, gravel, or other porous material. (but there are exceptions...) ...

exception: ... the landscape area is adjacent to permeable surfacing and no overspray or runoff occurs; or ....

exception:....the adjacent non-permeable surfaces are designed and constructed to drain entirely to landscaping (sloped), or the irrigation designer specifies an alternative design or technology as part of the Landscape Doc Package and clearly demonstrates strict adherence to irrigation system design criteria in Section 492.7. That's pretty clear, isn't it?

There's much much more.....

Concerned? Confused? Freaked out?

Don't be, we got it covered.


1158 26th St., #241
Santa Monica, CA 90403


"Atomic Irrigation........Irrigating the planet"
(in a AB 1881 world)

Ca. Dept of Water Resouces
Chanceofrain.com, 1881 bullet points

irrigation sprinkler