Landscape irrigation is one of the most common uses of recycled water. Because the characteristics of recycled water differ from potable water, adjusting landscape design and management practices when switching from potable to recycled water can help keep your landscape looking healthy. As with all landscapes, managers should consider the site's soil conditions, climate, and plant selection when developing management practices for recycled water landscapes.

Water Characteristics

Mountain View's recycled water meets strict water quality standards and is approved for many uses, including landscape irrigation. Recycled water typically differs from potable water in that it has higher levels of alkalinity, sodium, chloride, boron, and nitrogen. Landscape managers should consider these differences when planning soil amendments, plantings, and irrigation schedules. For example, additional watering may be needed to leach salts away from plant root zones.

Landscape Benefits of Recycled Water

Landscapes irrigated with recycled water offer some advantages over those irrigated with potable water. For example, using recycled water may reduce fertilizer needs due to higher nitrogen levels in recycled water compared to potable water. In addition, recycled water in Mountain View is not restricted during times of drought, so landscapes irrigated with recycled water may continue to be watered as usual during dry years- even if potable water use is restricted.

Plant Selection

Maintain a healthy landscape appearance by choosing plants that are not sensitive to salt and are otherwise appropriate for a site's conditions. See the links below for information on salt tolerance and plants suggested for recycled water landscapes.

Redwood Trees

Redwood trees' sensitivity to salinity poses a valid concern to landscape managers irrigating with recycled water. Practices that protect the health of redwood trees include: maintaining soil moisture in the root zone; testing and monitoring soil drainage, pH, and salinity; applying mulch around trees; avoiding compaction of the soil around trees; and monitoring trees regularly to address problems as they arise.

Mountain View is cooperating with the City of Palo Alto and the Palo Alto Regional Water Quality Control Plant to monitor redwood trees irrigated with recycled water. This study, which began in 2009, will provide insight into the effects of recycled water on redwood trees in Mountain View under different conditions.

Landscape Resources

As recycled water irrigation increases, scientists and landscape managers are improving their understanding and practices for its application. The links below represent some of the knowledge gained through research and hands-on experience with recycled water. In addition to these resources, Mountain View is among several local agencies cooperating with Water Reuse California to complete a new Bay Area Recycled Water Landscape Guide. This new guide will be released in 2013.

Links & Resources

• Salinity Management Guide - Water Reuse Association
• Redwood Tree Factsheet - South Bay Water Recycling
• Solutions Report - Santa Clara Valley Water District

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