Outdoor Residential Use Standard

Published: July 23, 2021

The Basics

  • The outdoor residential standard applies to both single family and multiple family housing units within a supplier’s service area.
  • The outdoor residential standard uses concepts like evapotranspiration, irrigation efficiency and landscape area (square feet) to calculate a water use budget for a supplier’s total residential landscapes.  The state will not provide/will not enforce landscape budgets for individual residential parcels.  More details provided below.
  • The state provided each supplier with residential landscape area (based on aerial imagery) for review. Total residential landscape area (in square feet) will be incorporated into a landscape water use equation/standard (provided by DWR) to produce a supplier level residential landscape budget in gallons.


August 2023

The State Water Board's proposed regulation includes the following:

Outdoor Residential Water Budget (gal/yr) = LAM x LEF x (ETo-Peff) x 0.62

Outdoor Residential Water Budget Factors




Landscape Area Measurement includes the following landscape types:

o   Irrigable-Irrigated (II),

o   Irrigable-Not-irrigated (INI) – up to 20%, through June 30, 2027

o   Special Landscape Areas (SLA), and

o   New

Aggregate data provided by DWR for all designations except for new landscapes installed after 2018.


Outdoor Residential Standard or landscape efficiency factor (unitless). 


Reference Evapotranspiration (inches per year). Provided annually by DWR.


Effective Precipitation (inches per year). Capped at 25% of total precip. and provided annually by DWR.


Conversion Factor to generate units in gallons per year.


Landscape Efficiency Factors (LEF) by landscape type and year

Compliance Date

Irrigable - Irrigated (II)

Irrigable-Not-Irrigated (INI)

Special Landscape Areas (SLA)

New Construction/ (1/2019)*

July 1, 2023





July 1, 2030





July 1, 2035






October 2022

Below is a summary of DWR’s recent Long Term Framework recommendations to the State Water Board as submitted on Thursday, September 29, 2022.

Note that these recommendations are subject to change per the final rulemaking process that allows for additional evaluation and public comment.  The State Water Board is expected to initiate final rulemaking in early 2023, as announced at CalWEP’s fall Plenary on September 8, 2022.

Residential Outdoor Standard:

    1. Established a reference evapotranspiration factor (ETF) of 0.80 and will decrease to an ETF of 0.63 by 2030 with no further recommendations to reduce.

    2. For new residential construction, the standard is established at 0.55 with potential to decrease based on future MWELO amendments.

    3. For Special Landscape Areas (SLA), like food gardens and recreational turf, the standard ETF is set at 0.80 and will decrease to an ETF of 0.63 with no further recommendation to reduce. Alternatively, suppliers can choose to include SLAs under the CII-DIM standard which is set to an ETF of 1.0.

    4. The Outdoor Residential Standard should be applied to 100% of irrigated landscape area and 20% of irrigable-not irrigated landscape area.

October 2021

Landscape Objective Equation

At the October 25, 2021  stakeholder meeting, DWR released revised recommendations for the outdoor standard ETAF. See slide below for summary. 

Landscape Area Measurement

DWR reported that provisional landscape area measurement data was delivered to retail suppliers earlier this year. DWR received feedback from 56% of retail suppliers. Currently, landscape area for 395 of the 398 retail water suppliers have been finalized and will be delivered "over the next couple of weeks."


August 2021

Landscape Area Measurement

All suppliers should have received their landscape imagery data by now.  DWR requested feedback/changes on individual supplier’s landscape measurement data by June 30th. DWR has until August 30th to provide landscape measurement files back to those agencies that requested changes. 

Landscape Objective Equation

DWR has also released a proposed landscape budget equation that will be used to determine a supplier’s residential outdoor budget and is seeking input. There has been much conversation about whether to use irrigated or irrigable landscape measurements to apply to the budget equation. 

On June 30, at the Standards, Methodologies and Performance Measures Workgroup meeting, DWR proposed:

    • ET adjustment factor of 0.7
    • Irrigable not irrigated (INI) used as buffer (20% of INI) - (Option 5 below)


  • June 30 – Water suppliers LAM data correction/ request for ongoing data corrections
  • June 30 – Standards and Methodology Workgroup Meeting, DWR proposed:
    • ET adjustment factor of 0.7
    • Irrigable not irrigated (INI) used as buffer (20% of INI)
  • August 30 – Deadline for DWR review submitted adjustment requests and deliver final LAM data to the suppliers
  • August 25, 10:00 AM - 12:30 PM
  • October 25 - Standards, Methodologies and Performance Measures Workgroup
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