Water efficiency must be considered from the initial irrigation system design phase through installation to ensure optimal performance. Consistent management and maintenance are also essential. Failure to do so can result in significant losses in system efficiency from poor management, improper system design, installation, or maintenance.
With the irrigation system hardware operating efficiently, it is important to consider the irrigation schedule, which dictates the amount and timing of the water applied. Water changes with the seasons, as should your irrigation schedule. Many landscapes are watered at the same level all year, adding unnecessary water for months at a time. Overwatering can cause more damage to plant materials than underwatering and can damage streets, curbs, other paving, and building foundations.
Outdoor water use efficiency has two facets.
- Designing a landscape that requires minimal supplemental water (see Best Management Practice (BMP) #4).
- Designing, installing, and maintaining an irrigation system that efficiently applies the appropriate amount of supplemental water, which is the topic of this BMP.
This BMP addresses ways to efficiently apply supplemental water that is added to make up the difference between landscape water requirements and the natural precipitation in your area. BMPs #4 and #5 work in tandem to make outdoor water use as efficient as possible.
Whether installing a new irrigation system or retrofitting an old one, there are many options to improve water efficiency. Most importantly, the person(s) responsible for the irrigation system should have proper training in system installation, maintenance, and management.
An important efficiency concept associated with irrigation systems is distribution uniformity, or how evenly water is applied over the landscape. Extra water is often applied because the system is not uniformly distributing water. When water isn't applied evenly, the landscape is watered to keep the driest spot green, grossly over irrigating other areas.
To maintain water efficiency in operations and maintenance, federal agencies should do the following.
- Recommend contractors be trained in water-efficient irrigation practices through partnerships, classes, seminars, and/or published guidance documents. Require specific training or certification for new or renewed contracts. Refer them to:
- The U.S. Environmental Protection Agency's (EPA) WaterSense program to learn about becoming WaterSense irrigation partners
- The Irrigation Association certification program
- Locally offered courses or seminars on water-efficient irrigation practices (check with your water utility or community colleges for availability).
- When hiring a vendor, inquire about the water efficiency knowledge of its personnel. Request a demonstration of practices that promote efficient irrigation. WaterSense can help you locate irrigation professionals in your area who have demonstrated knowledge in water-efficient irrigation.
- Review all irrigation service agreements annually to incorporate a high priority for water efficiency. Consider the following options:
- Incorporate a water budget, which can be used as a performance standard for water consumption. A vendor calculates your water needs and uses that information to plan an irrigation schedule to meet those needs
- Require a full audit of your irrigation system every three years by a qualified auditor, such as a WaterSense Irrigation Partner, that that meets the Irrigation Association’s Certified Landscape Irrigation Audit Program requirements or equivalent. This process is an in-depth assessment to determine your system's efficiency and distribution uniformity and to verify proper scheduling and system maintenance. The result of an irrigation audit will provide areas of improvement through scheduling, repair, and technology replacement.
- Require vendors to include immediate reporting and repair of problems in their maintenance programs and require regular, periodic maintenance routines as part of the overall irrigation maintenance program.
- Install an irrigation meter (sometimes known as a "deduct meter") to measure the water applied to the landscape. Work with your water utility to use the metered data as a credit toward the sewer charges if sewer is not metered. Require your maintenance vendor to keep a record of all irrigation water use as part of its maintenance program.
- Verify that the irrigation schedule is appropriate for the climate, soil conditions, plant materials, grading, and season.
- Change your schedule based on changing weather conditions and as part of periodic maintenance. Require your maintenance vendor or auditor, or both, to deliver options for automating schedule changes based on changing weather conditions. (See Retrofit Options below for information about weather-based irrigation controls.)
- Generally, it is better to water deeply and less frequently than to water lightly and often. A deep, less frequent schedule encourages deep roots and healthy plants. Set your irrigation schedule to take this into consideration.
- Certain soil types or steep slopes may increase the chance of surface runoff. For these landscape types, irrigation events may need to be divided into multiple applications (commonly known as a cycle and soak schedule). Implement a landscape-specific cycle and soak schedule. If currently installed irrigation controllers are not capable of such programming, replace them with current technology.
- To reduce evaporation, set your schedule for early morning when wind is less likely and the temperature is cooler.
- In addition to a full system audit every three years, periodically monitor the irrigation system for misaligned or broken heads throughout the irrigation season. Ask vendors to produce and implement a program that makes sure certain sprinkler components are placed and adjusted so they will water the cultivated plants and not the pavement. Verify that irrigation system pressure is within manufacturer specifications. To help ensure uniformity, require that replacement equipment be compatible with existing equipment.
- Always attach shut-off nozzles to handheld hoses.
The following retrofit options help federal agencies maintain water efficiency across facilities.
- Replace a timer-based irrigation controller with an advanced control system that waters plants only when needed based on weather or soil conditions. Many available technologies use weather or soil moisture information to schedule irrigation according to plant needs. A few options to discuss with your service provider, auditor, or consultant or designer include:
- A weather-based irrigation control system is an irrigation controller or device that can be added to an existing controller. It uses real-time weather information along with landscape parameters entered by the vendor to schedule irrigation only when plants need water. If a weather-based system is installed, make sure the controller has a "deficit irrigation" setting for manual adjustment of the controller to irrigate less than the required amount. Some weather-based irrigation control systems use historical weather data instead of real-time data. These systems are not preferred because real-time data provide much more accurate accounting of the plants' water requirements and have a larger reduction potential.
- A soil-moisture-based irrigation control system uses a soil moisture sensor that is inserted into the soil of each zone to measure moisture content. It can be connected to an existing controller or add-on device, enabling irrigation when only the plants need water.
- A central irrigation control system uses demand-based controls and enables a water manager to centrally operate and manage multiple irrigation systems at multiple locations using various means of communication. A centralized control system can use weather-based or soil moisture-based sensors to set the irrigation schedule.
- Replace trees, shrubs, and landscaped beds irrigation systems with low-flow, low-volume irrigation (also called micro-irrigation or drip irrigation). Many plant beds do not require the spray heads traditionally used to water turf areas. Drip irrigation can be more efficient because water is slowly and directly applied to plant root zones, minimizing evaporation and runoff.
- Increase the efficiency of the system's sprinkler heads. Sprinklers with a fine mist are susceptible to water waste from wind drift. Also, some sprinklers don't apply water evenly over the landscape. Sprinkler heads can often be replaced with more efficient heads designed to minimize water lost to wind and to more uniformly distribute water.
- Install sensors that provide real-time data to adjust irrigation scheduling based on conditions:
- Install rain-sensing technology that can automatically shut off the irrigation system during rain events (called rain delay). Many cities and some states require rain-sensing technology by law. Check with your state or city about relevant mandates.
- Install soil-moisture-sensing technology on your system to prevent irrigation when the soil has sufficient moisture.
- Install wind-sensing technology to interrupt irrigation cycles in the presence of significant wind.
- Install freeze-sensing technology to prevent irrigation during freeze conditions.
- Get information on these "smart" irrigation controls from the Irrigation Association’s Smart Water Applications Technologies Program.
The following replacement options help federal agencies maintain water efficiency across facilities:
- When installing a new system, hire an irrigation design company that has experience in designing water-efficient systems, such as one that employs WaterSense Irrigation Partners. Also ensure that the installation and maintenance vendor has a background in water efficiency.
- Upon completion of new irrigation systems, hire a qualified irrigation auditor, such as a WaterSense Irrigation Partner, to audit the irrigation system to determine if baseline efficiencies are compatible with design intent and to make minor adjustment recommendations as needed.
- Require that your system be designed, installed, and maintained according to irrigation best management practices published by local cooperative extensions and irrigation or landscape trade associations. Following industry best management practices helps your irrigation contractor address efficient and water-conserving techniques from design through installation and proper maintenance. Visit the Irrigation Association for information related to the most widely known irrigation best management practices.
- Design your system for maximum water distribution uniformity. Discuss the following with your designer:
- Do not directly distribute water over impermeable surfaces or nontarget areas.
- Maximize sprinkler distribution uniformity by following manufacturer recommendations for head spacing. Consider necessary spacing reductions to compensate for prevailing wind.
- Create irrigation hydrozones by grouping turf and plants with similar water needs. Also consider varying soil conditions, sun/shade/wind exposure, slope, and other site specifics that may impact watering needs.
- Install the following components for optimal water efficiency:
- Drip or micro-irrigation for all areas suitable for such technology
- Check valves in all sprinklers to retain water in lateral pipes between cycles
- Advanced demand-based irrigation controls (weather or sensor based controls)
- Moisture freeze and wind sensors to interrupt irrigation during unfavorable weather conditions
- Flow rate monitoring equipment that can interrupt irrigation if excess flow is detected. (caused by broken pipes, fittings, nozzles, emitters, sprinklers, etc.).
- Consider all sources of alternative water (see BMP #14) where environmentally appropriate and where allowed by local regulations to offset the use of freshwater.