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Best Management Practice #5: Water-Efficient Irrigation

Water efficiency must be considered from the initial irrigation system design phase through installation to ensure optimal performance. Consistent management and maintenance is also essential. Failure to do so can result in losing more than 50% of irrigation water due to evaporation, wind, poor management, and/or 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. Over-watering can cause more damage to plant materials than under-watering and can damage streets, curbs, other paving, and building foundations.

Overview

Two facets of outdoor water use efficiency exist:

  1. Designing a landscape that requires minimal supplemental water (see Best Management Practice (BMP) #4)
  2. Designing, installing, and maintaining an irrigation system that applies the appropriate amount of supplemental water in an efficient manner

This best management practice addresses ways to be efficient in the application of supplemental water that must be added to make up the difference between landscape water requirements and the natural precipitation in your area. Best management practices 4 and 5 work in tandem to make outdoor water use as water 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 distributing water in a uniform manner. When water isn't applied evenly, the landscape is watered to keep the driest spot green, grossly over-irrigating other areas.

Operation and Maintenance

To maintain water efficiency in operations and maintenance, Federal agencies should:

  • Recommend existing contractors become familiar with water-efficient irrigation practices through partnerships, classes, seminars, and/or published guidance documents. Refer them to:

    • The U.S. Environmental Protection Agency's (EPA) WaterSense program to learn about becoming a WaterSense irrigation partner.

    • Locally-offered courses or seminars on water-efficient irrigation practices (check with your water utility or community colleges for availability).

    • Best management practices and guidance documents. Many local cooperative extensions and irrigation trade associations provide best management practice and guidance documents online.

  • When hiring a vendor, inquire about the water efficiency knowledge of their personnel. Request a demonstration of practices that promote efficient irrigation. WaterSense can help you locate irrigation professionals in your area that 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 partner. This process is an in-depth assessment of your system and its performance to verify proper scheduling and to expose growing deficiencies from changes, growth of landscape, or an aging system as well as opportunities to employ new technologies.

  • Require vendors to include immediate reporting and repair of problems in their maintenance programs and also 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 amount of water applied to the landscape. Some water utilities offer an interruptible rate for the service or will provide a credit to the sewer charges. Your maintenance vendor should keep a record of all irrigation water use as part of its maintenance program.

  • Verify that the irrigation schedule is appropriate for climate, soil conditions, plant materials, grading, and season.

    • Change your schedule based upon changing weather conditions and as part of regular, periodic maintenance. Require your maintenance vendor and/or auditor to deliver options for automating schedule changes based on changing weather conditions.

    • Certain soil types or steep slopes may increase the chance of surface runoff. Irrigation events may need to be broken up into multiple applications depending on landscape conditions. This is commonly known as a "cycle and soak" methodology. Ask your maintenance vendor to assemble and implement such schedule parameters as necessary. If currently installed irrigation controller(s) is/are not capable of such programming, replace it/them with current technology.

    • Generally, it is better to water deeply and less frequently than to water lightly and often. A deep, less frequent schedule encourages deep roots resulting in healthy plants. Ask your vendor to produce and implement a program that takes into account the optimal water window and other scheduling requirements that relate to the actual landscape being maintained.

    • In addition to a full system audit every three years, periodically monitor for effectiveness throughout the irrigation season. Ask your vendor to produce and implement a program that makes sure certain sprinkler components are placed and adjusted so that they will water the cultivated plants and not the pavement. Verify that irrigation system pressure is within manufacturer specifications. To help ensure consistent uniformity, require that replacement equipment is compatible with existing equipment.

  • Always attach shut-off nozzles to handheld hoses.

Retrofit Options

The following retrofit options help Federal agencies maintain water efficiency across facilities:

  • Replace existing irrigation system controllers with a more advanced control system that waters plants only when needed. There are many available technologies that use weather or soil moisture information to schedule irrigation according to plant needs. Below are a few options to discuss with your service provider, auditor, or consultant/designer:

    • Weather-based irrigation controls are an irrigation controller or device that can be added to an existing controller. They use real-time or historical weather information along with landscape parameters entered by the vendor to schedule or allow for irrigation 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.

    • Soil-moisture-based irrigation controls are inserted into the soil to measure moisture. They can be connected to an existing controller or add-on device, enabling irrigation when only the plants need water.

    • Complete central control systems utilize demand-based controls and enable a water manager to centrally operate and manage multiple irrigation systems at multiple locations using various means of communication.

  • Replace applicable trees, shrubs, or plant beds 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 due to slow and direct water application 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. Existing sprinkler heads can often be exchanged with more efficient heads designed to minimize water lost to wind and distribute water in a more uniform manner.

  • Install rain-sensing or soil-moisture-sensing technology on your system to prevent irrigation from taking place during periods of sufficient moisture. Many cities, and some states, require rain-sensing technology by law. Check with your state or city on relevant mandates.

  • Install wind-sensing technology to interrupt irrigation cycles in the presence of significant wind.

  • Install freeze-sensing technology to prevent irrigation during freeze conditions.

Replacement Options

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 partners. Also ensure that the installation and maintenance vendor has a background in water efficiency.

  • Upon completion of new irrigation systems, audit the irrigation system using a qualified irrigation auditor, such as a WaterSense partner, 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 application uniformity (distribution uniformity). Discuss the following with your designer:

    • No direct distribution of water over impermeable surfaces or non-target 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/micro irrigation for all areas suitable for such technology.

    • Check valves in all sprinklers to retain water in lateral pipes between cycles.

    • Demand based irrigation controls (i.e., weather or sensor based controls).

    • Rain/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. (i.e., caused by broken pipes, fittings, nozzles, emitters sprinklers, etc.).

  • Use alternative sources of water (see BMP #14) where environmentally appropriate and local regulations allow.

Resources

The following resources provide guidance on water best management practices.