Traditional landscapes require supplemental water to thrive in most locations. Kentucky bluegrass, for example, is native to regions that receive in excess of 40 inches per year of precipitation, but it is commonly planted in areas across the country that receive much less precipitation.
Outdoor water use efficiency has two facets:
- Designing a landscape that requires minimal supplemental water—the topic of this best management practice (BMP).
- Designing, installing, and maintaining an irrigation system that efficiently applies the appropriate amount of supplemental water. (see BMP #5).
This BMP addresses only water-efficient landscaping. BMP #5 provides specific information on water-efficient irrigation. Irrigation is supplemental water that must be added to make up the difference between landscape water requirements and the natural precipitation in your area.
Depending on climate, landscape irrigation may compromise a substantial portion of a facility's overall water use. Therefore, integrating water-efficient landscaping as part of an overall water efficiency program is important.
Water-efficient landscapes using native and other climate-appropriate plant materials can reduce irrigation water use to better withstand drought, reduce drought loss or damage, and require less time and money to maintain. Water-efficient landscaping also includes maintenance techniques that create a landscape that requires less water.
To maintain a water-efficient landscape, federal agencies should:
- Periodically review all landscape service and maintenance agreements to incorporate a high priority for water, chemical, and energy efficiency
- Consider hiring landscape contractors who focus on water-efficient or climate-appropriate landscaping. Recommend contractors attend courses or seminars to learn these techniques. Consider using landscape professionals who are certified as U.S. Environmental Protection Agency (EPA) WaterSense Irrigation Partners. These partners must be trained specifically in efficient landscape practices.
- Require landscape contractors to report and fix problems. Many landscape contractors not only install and maintain plants in your landscape, but also install and maintain the irrigation system. These contractors can identify and report leaks and other inefficiencies in the landscape
- Add mulch to plant beds. Mulch decreases water lost from soil through evaporation and helps reduce weed growth
- Maintain a sufficient quantity of topsoil rich in organic matter, 4 to 6 inches, to capture storm water as it falls and to release moisture back to plants over time. The result reduces irrigation requirements
- Aerate soil seasonally in turf areas and landscape beds to introduce oxygen into the soil's deep layers and break up compacted soil. This allows water to penetrate deeply into the soil, producing a healthier root system
- Recirculate water in decorative fountains, ponds, and waterfalls. Shut off these features when possible to reduce evaporation losses. Check water recirculation systems annually for leaks and other damage. Consider using non-potable water in these systems (see BMP #14)
- Alternate turf mowing height between low and high levels. This encourages roots to grow deeply and allows plants to go longer between watering sessions
- Keep irrigated landscape weed free so valuable water is consumed only by decorative landscape.
The following retrofit options help federal agencies maintain water-efficiency landscapes across facilities.
- Select drought-tolerant or climate appropriate turf, trees, shrubs, and ground cover when replanting landscaped areas.
- Minimize the area of turf in your landscape. Most turf requires substantially more water than planted beds, especially if the plants are climate-appropriate and covered with mulch.
- Eliminate "strip grass" to the greatest extent possible. Small strips of grass, common in parking islands and between sidewalks and the roadway, are hard to maintain and difficult to water efficiently. Use bushes, mulch, or permeable hardscape in these areas instead.
- Implement low-impact development techniques, such as making parking lot island depressions instead of raised curb areas to capture and retain storm water.
The following replacement options help federal agencies maintain water efficiency across facilities.
- Replace or install the entire landscape with climate-appropriate, water-efficient plant material. You may be able to design a landscape that doesn't require supplemental water.
- Design the landscape so plants with similar water needs are grouped together (called hydrozoning). This allows for more efficient irrigation.
- Ensure the landscape is properly designed from the start. Hire a licensed landscape architect or a qualified site planner/designer. Designing with water efficiency in mind limits the clearing of native vegetation. This increases recharge and limits surface runoff, thereby limiting the size of storm water management facilities. Consider using a landscape designer that is certified as an U.S. Environmental Protection Agency (EPA) WaterSense Irrigation Partner.
- Test soil nutrients and pH levels prior to installing a landscape. Depending on type, soil may need to be amended to ensure water is delivered to the plant in an efficient manner (i.e., good absorption and water holding capacity).
- Use turf only where it is needed, such as athletic and training fields, avoiding areas where it will not be utilized or in long narrow areas that cannot be irrigated effectively.
- Ensure trees are planted at the appropriate depth.
- When designing new landscape, avoid the use of ornamental water features to minimize water use.