California Water Use Ordinance Mandates New Approaches for Landscape Construction Projects

by Isaac Swanson and Ingrid Morken

California’s water use regulations are complex and often times difficult to navigate for compliance depending on the project type. According to to the California Water Boards, “our changing climate requires Californians to use water more wisely … small changes make a big impact.” The Model Efficient Landscape Ordinance (MWELO) requires a number of design approaches to maximize water conservation.

WRA’s design for Yosemite Slough State Park in San Francisco will comply with state water use requirements by using recycled water for irrigation and low water use plants (rendering by WRA, Inc.).

In July 2015, California Governor Edmund G. Brown Jr. signed MWELO in to law to reduce water use in California in the midst of a severe drought. It mandates a reduction in water use for qualified new landscaping and projects with more than 500 square feet of irrigated area and landscape renovation projects with more than 2,500 square feet of irrigated area. The state delegates responsibility for implementing the ordinance to local and county government agencies responsible for reviewing construction permit submittals.

Not all new landscaping projects are required to follow MWELO.  For example, temporarily-irrigated environmental restoration projects, mined-land reclamation projects, registered historical sites, edible gardens, sports fields, golf courses, publicly-accessibly arboretums, and all projects irrigated with recycled water are currently exempt from the regulations. Other projects, such as parks, permanently-irrigated restoration projects, residential and commercial developments, and educational facilities irrigating with potable water sources are not.

MWELO calls for new approaches to soil amendments, mulching, and planting in addition to irrigation. For instance, MWELO requires:

  • using drought-tolerant plantings;
  • arranging plants in groups with similar water needs;
  • applying 3 inches of locally-sourced mulch to tree and shrub planting areas; and
  • incorporating at least 1.33 to 2 inches of organic compost into soil.

The ordinance also mandates installing water-conserving irrigation components such as master valves that regulate the amount of time that water flows through irrigation systems, irrigation clocks with climate sensors that automatically turn off irrigation systems when it rains, and flow sensors that automatically shut down irrigation systems when pipes break or leak.

Some local agencies set even more stringent local water use ordinances. “San Francisco’s Recycled Water Use Ordinance requires existing and proposed landscaping and restoration projects in many parts of the city to be irrigated with recycled water, so we designed the irrigation system for Yosemite Slough to be compatible with recycled water once it becomes available,” says Swanson.

Landowners can expect MWELO to become more stringent as time goes on. The state will likely issue updates to the ordinance in late 2018 or 2019.

California water use regulations require shrub planting beds like those at Robin Sweeny Park in Sausalito to be mulched to conserve water (photo by Isaac Swanson).

If your landscape construction project involves long-term irrigation, working with a licensed landscape architect with irrigation experience will ensure that the planting and irrigation design are compliant with all codes and ordinances. “Many landscape architects outsource irrigation work, but including irrigation in our design services at WRA helps our clients comply with water use regulations, get permits, and meet success criteria for their projects,” says Swanson. One thing is for sure: adapting to a water scarce future means embracing an ever-evolving set of water-conserving practices and technologies and constantly asking how we can better conserve this precious resource.