May - June 2010
Vol. 73 No. 3


Making all our landscapes water-wise landscapes

Water efficient landscapes are dynamic and colorful. Photo by Mark Schroeder.

In California, about half of all urban water use is for watering landscapes. There is no debate about the value of landscapes. They help clean air and moderate temperature. They beautify and soften urban environments, screen noise and unpleasant sights, and serve as refuges for people, birds, and other wildlife. Maintaining desired landscapes while sustainably managing limited water can be a delicate balance, but it does not need to be a struggle. Even in California a lush and vibrant landscape is compatible with minimizing supplemental irrigation.

In California two main factors influence landscape water use: plant selection and irrigation efficiency. A landscape design with the right plants in the right place, considering factors of microclimate, soil type, slope, and sun exposure, can make a natural oasis that requires little maintenance rather than a demanding water-thirsty nightmare.

You need to select plants native to your locale, and place them according to their tolerances for heat, cold, sun, and shade. Native plants will generally require the least maintenance, and should not need much supplemental irrigation after initial establishment.

Turf grass, on the other hand, while it's so common in yards and provides a good playing surface for small children and pets, can translate into a hole in your watering budget. One of the quickest ways to reduce irrigation is to replace such high-water landscapes with drought-tolerant and native plants, and/or permeable hardscape.

An efficient irrigation system will apply water only as necessary to desired areas, rather than to hardscape or weeds. Do not apply water faster or more frequently than your soil can absorb it. Sandy soils are more porous and need more frequent watering. In the Bay Area, particularly on South Bay clayey soils, water needs to be applied slowly and infrequently. On slopes, reduce runoff by using drip irrigation rather than overhead spraying. Water waste is illegal in some areas, and it can damage hard surfaces and potentially create liability.

Non-potable water can provide another alternative for landscape irrigation. Recycled water is currently used extensively in non-residential landscapes, and graywater and rainwater-harvesting systems are moving into residential backyards.

In most regions of California, homeowners and businesses can find incentive programs for water-efficient landscaping. Local governments have developed landscape-irrigation audit programs, rebates for landscape renovation, irrigation-hardware upgrades or repair, and educational resources. Contact your local agency to learn more about its water-efficiency program.

State mandates landscape water efficiency

Water efficient landscapes are dynamic and colorful. Photo by Chris Pedersen.

Last September the Department of Water Resources adopted an updated Model Water Efficient Landscape Ordinance. State law (AB 1881 of 2006) requires cities and counties to adopt DWR's Model Ordinance or one "at least as effective" in reducing landscape water usage.

The Model Ordinance applies to most new and rehabilitated landscapes over 2,500 square feet, or for homeowner-installed single-family new construction over 5,000.

Project applicants must provide professionally prepared landscape and irrigation plans that will not exceed a maximum applied water allowance. A worksheet is required with water-budget calculations and hydrozone tables. Some projects may require dedicated irrigation meters.

The Model Ordinance is aimed at eliminating inefficient irrigation. It prohibits overhead sprinkling in areas less than eight feet wide or within 24 inches of non-permeable hardscapes. It also requires drip irrigation or other low-volume irrigation on slopes greater than 25%, and weather- or evapotranspiration-based irrigation controllers for all automatic irrigation systems. Planting designs must group plants by water needs.

Several regional entities have worked together to develop local template ordinances to streamline requirements and achieve greater water savings. Members of the Bay Area Water Supply and Conservation Agency (BAWSCA) collaborated on a template designed to achieve up to 25% water savings on landscape projects. BAWSCA agencies receive Hetch Hetchy water from the San Francisco Public Utilities Commission, and are faced with limited water-supply allocations. Additional regional template ordinances were developed by the Bay-Friendly Coalition through Alameda County's, and in Santa Clara County. Regional collaboration helps developers and architects by homogenizing requirements and presenting a consistent message of conservation to residents and businesses.

The state is also mandating that cities and counties adopt a first-in-the-nation mandatory Green Building Standards Code (CALGreen), setting energy, water, and overall-sustainability criteria for new construction. Since the required CALGreen standards and landscape ordinance face similar timelines for adoption, some agencies have opted to incorporate the landscape water-efficiency requirements into their update to the Green Building Program.