TO: Board of Supervisors
FROM: Brian D. Bordona - Director of Planning, Building and Environmental Services
REPORT BY: Emily Hedge, Planner III
SUBJECT: Adopt an Ordinance amending Chapter 18.118 Water Conservation Regulation for Landscape Design
RECOMMENDATION
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Adopt an Ordinance of the Napa County Board of Supervisors, State of California, amending Chapter 18.118 (Water Conservation Regulations for Landscape Design) of Title 18 (Zoning) of the Napa County Code to achieve consistency with the California Code of Regulations Title 23, Division 2, Chapter 2.7 Model Water Efficient Landscape Ordinance and repeal Resolution No. 92-161 establishing the existing Water Conservation in Landscape Guidelines. (No Fiscal Impact)
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BACKGROUND
The California Department of Water Resources (DWR) Model Water Efficient Landscape Ordinance (MWELO) is a statewide water efficiency regulation for new development and retrofitted landscapes in California. The MWELO provides definitions, technical information, and sample documents for the development of water efficient landscapes. All local agencies must adopt, implement, and enforce the MWELO or a local Water Efficient Landscape Ordinance that is at least as efficient as the MWELO. In 1992, the County adopted its own provisions through Napa County Code (NCC) Chapter 18.118 and Landscape Guidelines by Resolution. These documents have not been amended to date. Since the NCC has not been updated to stay current with State code, there are portions of the code that are no longer “as efficient” as the MWELO. On December 17, 2025, at a duly noticed public hearing, the Napa County Planning Commission recommended that the Board of Supervisors adopt the proposed revisions to the existing NCC provisions. Therefore, Staff recommends that the Board of Supervisors adopt the proposed ordinance codifying the changes and repeal Resolution No. 92-161, which established the existing Water Conservation in Landscape Guidelines.
State Requirement
The California Department of Water Resources (DWR) Model Water Efficient Landscape Ordinance (MWELO) is a statewide water efficiency regulation for new development and retrofitted landscapes in California. The text of California Code of Regulations (CCR) Title 23, Division 2, Chapter 2.7 Model Water Efficiency Landscape Ordinance can be viewed online through a link on the DWR website - https://water.ca.gov/Programs/Water-Use-And-Efficiency/Urban-Water-Use-Efficiency/Model-Water-Efficient-Landscape-Ordinance. The MWELO is also referenced by Title 24, Part 11, Chapters 4 and 5 CalGreen Building Code.
The MWELO is a model for local agencies to enforce minimum standards for water use efficiency in landscape design, construction, and management. It achieves this through specific requirements related to soil, plants, irrigation, stormwater, and nonportable water supplies to improve California’s conditions in the built environment and provide benefits and realize sustainability goals. The MWELO provides definitions, technical information, and sample documents for the development of water efficient landscapes. All local agencies must adopt, implement, and enforce the MWELO or a local Water Efficient Landscape Ordinance that is at least as efficient as the MWELO.
In 1992, the Napa County Board of Supervisors adopted Ordinance No. 1029, adding Chapter 18.118 (Water Conservation Regulation for Landscape Design) to the Napa County Code and implementing a local water conservation program through Landscape Guidelines adopted by Resolution No. 92-161 (Attachment C). The resolution found that Napa County’s unique circumstances warranted a locally tailored ordinance rather than a statewide, one-size-fits-all approach.
Chapter 18.118 and the Landscape Guidelines have not been amended since 1992. Since that time, the Department of Water Resources (DWR) amended the Model Water Efficient Landscape Ordinance (MWELO) in 2009 and 2015, and most recently issued revised regulations and appendices in January 2025. As a result, portions of the NCC no longer meet current state water efficiency standards.
State law requires local land use authorities to ensure MWELO compliance for new development projects with 500 square feet or more of landscaped area, and for rehabilitated landscape projects with 2,500 square feet or more. This requirement applies to residential, commercial, industrial, and institutional projects that require permits, plan checks, or design review. To meet these standards, County staff currently direct applicants to comply with the MWELO rather than the NCC (Chapter 18.118 or the County’s Landscape Guidelines).
Although the NCC and Landscape Guidelines share many definitions and general requirements with the MWELO, the MWELO includes more detailed and current calculation factors, equipment standards, and data sources. Recent revisions also incorporate significantly expanded location-specific information for Napa County, enabling more precise calculations and improved operational standards.
A few examples of differences between current MWELO and NCC include:
Applicability of Project Types
• MWELO - Applies to residential, commercial, industrial, and institutional projects that require a building or landscape permit, plan check, or design review.
• NCC - The County code lists “Homeowner-provided landscaping for single-family and multifamily projects” as exempt from evaluation under the County Landscape Guidelines.
Local Reference Data - The “reference evapotranspiration” or “ETo”, is a standard measurement of environmental parameters which affect the water use of plants.
• MWELO - Appendix C. Reference Evapotranspiration (ETo) includes 12 locations throughout the County: Napa County, American Canyon, Angwin, Calistoga, Deer Park, Moskowite Corner, Napa, Oakville, Rutherford, Silverado Resort, St. Helena, Yountville.
• NCC - Landscape Guidelines include three (3) locations, one of which is in Solano County: St. Helena, Yountville, Benicia (Solano County)
Plant Factor Categories - “Plant Factor” is a factor, when multiplied by ETo, estimates the amount of water needed by plants.
• MWELO - Includes four categories: very low, low, moderate, and high water use plants
• NCC - Includes two categories: low and high
ET adjustment factor (ETAF) Calculations - ETAF means a factor that, when applied to reference evapotranspiration, adjusts for plant factors and irrigation efficiency, two major influences upon the amount of water that needs to be applied to the landscape.
• MWELO - Includes separate calculations for residential, non-residential, “special landscape areas”, and existing non-rehabilitated landscape areas.
• NCC - Includes one (1) factor for all project types.
Irrigation Efficiency Rates - “Irrigation Efficiency” (IE) means the measurement of the amount of water beneficially used divided by the amount of water applied and is expressed as a percentage. Irrigation efficiency is derived from measurements and estimates of irrigation system characteristics and management practices.
• MWELO - Contains separate rates for overhead and drip irrigations systems. The rates are based on higher efficiency equipment and operations.
• NCC - Contains one (1) rate.
Proposed Text Amendment
Attachment A “Proposed Ordinance - Redlined” presents the proposed edits, shown in strikethrough and underline. The primary proposed change is to include direct references to California Code of Regulations (CCR) Title 23, Division 2, Chapter 2.7. Attachment B “Proposed Ordinance - Clean” shows the final ordinance language, should the ordinance be amended as proposed.
Since the MWELO is comprehensive and covers the requirements currently contained in NCC 18.118, most of the individual lists of requirements included in NCC can be removed, resulting in a more concise code section. County specific regulations regarding violations (NCC Sec.18.118.040 - Violations) remain unchanged.
The provisions of Napa County Board of Supervisors Resolution No. 92-161 would be repealed in their entirety, and the Napa County Water Conservation in Landscape Guidelines would be replaced with the requirements provided in the MWELO.
Benefits
In addition to ensuring compliance with State standards, the updated code will result in the following benefits:
• The use of standardized documents simplifies the overall review process for both applicants and staff. MWELO includes Appendix A. Sample Water Efficient Landscape Worksheet and Appendix B. Sample Certificate of Completion Package.
• More efficient documentation for the required annual reporting to DWR. Local agencies are required to report on implementation annually by January 31 of each year to DWR’s Water Use Efficiency Branch.
• The direct reference to the CCR ensures that code language does not become inconsistent with State regulations or requirements.
• The direct reference to the CCR removes the need to go through the Text Amendment process to update County code following future revisions to the MWELO. The DWR’s mandatory three-year update cycle begins January 1, 2026.
Planning Commission Recommendation
On December 17, 2025, at a duly noticed public hearing, the Napa County Planning Commission recommended that the Board of Supervisors adopt the proposed ordinance (Attachment D).
Additional Information
Today’s public hearing was noticed in the Napa Valley Register on Thursday, January 15, 2026. The same notice was also emailed to the PBES’s Interested Parties List that same day. At the time of publishing, staff have not received any public comment.
Procedural Requirements
1. Open Public Hearing.
2. Staff report.
3. Public comments.
4. Close Public Hearing
5. Motion, second, discussion and vote on intention to adopt the Ordinance and repeal Resolution 92-161 in its entirety.
FISCAL IMPACT
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Is there a Fiscal Impact? |
No |
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Is it Mandatory or Discretionary? |
Discretionary |
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Discretionary Justification: |
If Chapter 18.118 is not amended, it will be inconsistent with state law and could create confusion by the regulated community who might rely on the County Code instead of State Law. |
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Is the general fund affected? |
No |
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Future fiscal impact: |
None |
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Consequences if not approved: |
PBES would have to follow existing ordinance provisions and state law, which may create confusion and impede implementation. |
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Additional Information: |
Champion Environmental Sustainability and Resilience |
ENVIRONMENTAL IMPACT
ENVIRONMENTAL DETERMINATION: The Board finds that the adoption of this ordinance will not have a significant effect on the environment and is exempt from the California Environmental Quality Act pursuant to Categorical Exemption Class 8 (“Actions by Regulatory Agencies for the Protection of the Environment”) which may be found in the guidelines for the implementation of the CEQA at 14 CCR §15308; and the General Rule in that it can be seen with certainty that there is no possibility the proposed action may have a significant effect on the environment and therefore the CEQA is not applicable. [See Guidelines for the Implementation of the CEQA 14 CCR §15061(b)(3).]