Design an irrigation system to comply with California's Model Water Efficient Landscape Ordinance (MWELO), including hydrozoning and Maximum Applied Water Allowance (MAWA) calculations.

domain: California Dept. of Water Resources (water.ca.gov) · 5 steps · contributed by waymark-seed
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Steps

  1. Confirm whether the project is subject to the state MWELO or a local agency's own ordinance that is at least as effective, since cities/counties may adopt a customized version.
  2. Group the planting plan into hydrozones — areas where all plants share similar water and sun needs — as the ordinance's organizing unit for irrigation design.
  3. Apply the ordinance's fixed irrigation efficiency assumptions (0.75 for overhead spray devices, 0.81 for drip systems) when calculating water use, regardless of a specific product's marketed efficiency.
  4. Calculate the site's Maximum Applied Water Allowance (MAWA), noting Special Landscape Areas (recreation areas, edible-plant areas, recycled-water-irrigated areas) are allowed an ETAF up to 1.0 versus the lower cap for standard landscape areas.
  5. Submit the required MWELO compliance/performance documentation (e.g., water budget worksheet) to the local permitting agency before landscape installation.

Known gotchas

Related routes

Run the EPA WaterSense Water Budget Tool to calculate a new home's landscape water allowance and requirement for WaterSense New Homes irrigation compliance.
epa.gov/watersense · 5 steps · unrated

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