Going Green by Saving Water

March 31, 2010
Efficient irrigation design and practices save money on water and energy

The primary focus of the green building movement has been on energy – until recently. Water efficiency is moving to the top of the green building checklist, and building professionals are playing a key role in the shift. The old, wasteful ways are going away as consumers realize that water is a finite resource affected by our growing population and changing climate.

In the most recent version of its LEED rating systems, the USGBC has increased the emphasis on water efficiency. ASHRAE’s Standard for the Design of High-Performance Green Buildings,189.1 includes a performance option requiring a 50 percent reduction in outdoor water use. Some states are instituting landscape ordinances, such as California’s Model Water-Efficient Landscape Ordinance.

Compelling facts are driving these changes. Across the globe, water consumption tripled from 1950 to 2000. In the United States, the population increased nearly 90 percent from 1950 to 2000, but water withdrawals increased 127 percent, according to the U.S. Geological Survey (USGS). Compounding the urgency, most of the population growth expected over the next two decades is taking place in the driest parts of the country, which already have the highest per capita water use (see map).

While much of the public water supply goes to residential use, the USGS estimates about 17 percent goes to commercial and institutional (CI) buildings. A report released in 2000, Commercial and Institutional End Uses of Water, estimates that CI buildings consume 15 to 25 percent of municipal water supplies. Landscape water is a significant part of a commercial building’s water consumption (see chart). For example, the facilities manager of a Los Angeles office building using 3 million gallons of landscaping water per year would save 600,000 gallons and $1,800 on water bills by reducing irrigation usage by 20 percent.

Alternative Water Sources: Untapped Potential or Unforeseen Cost?

Rainwater, onsite recycled wastewater, and municipally supplied reclaimed water – these are a few of the many water sources beyond the tap. But in some green building circles, the jury is still out on whether buildings should bank on these technologies to save water.

While gaining popularity in the green building scene, alternative sources can come at a price. Some alternative sources require tremendous energy to pump or purify, making the tradeoff less attractive.

In the midst of the debate, green building professionals around the country tend to agree on one point: water is water, no matter what the source. Water is a finite resource, and having an alternative water source shouldn’t replace water efficiency measures. For example, using rainwater to water a landscape with a poorly designed irrigation system and wasteful schedule is no better than efficiently watering a landscape with potable water. Whether it’s rainwater running off the roof or potable water from the city hookup, water remains a limited resource.

The bottom line? Get ahead of the curve and save money. Here are six rules of thumb for building professionals to save a little "blue" in their greening efforts.

1. You Can’t Manage What You Don’t Measure 
Many building professionals don’t know how much of their water use goes to landscaping. While metering for entire buildings is required in many jurisdictions, few buildings have submeters for specific end uses like irrigation.

Submeters allow building managers to track landscape water use and target reductions. Leaks are easily detected, preventing a situation where a cracked pipe or broken sprinkler head goes unnoticed. Submeters can save on sewage bills: some utilities offer a credit on sewer charges if a property can document that a portion of the water went outdoors rather than down the drain. Your documentation can also be used to publicize your building professionals’ success in conserving water.

2. Efficient Water Use Starts with Smart Landscaping 
No matter how it’s irrigated, lush landscaping will always be thirstier than native species. As a result, choosing an appropriate plant palette is a first consideration in water-efficient landscaping.

According to the Federal Water Efficiency Best Management Practices, native and other climate-appropriate plant species can stand up better to drought, reduce irrigation water use by more than 50 percent, and require less time and cost to maintain. Smaller turf and other irrigated areas further reduce mowing, fertilizing, landscape debris removal, and other maintenance.

Plan a plant palette that can survive on rainfall alone. In many regions of the country, natural rainfall can sustain landscaping once the plants mature. When supplemental irrigation is necessary, tools like EPA’s WaterSense Water Budget Tool help to create an efficient landscape (see sidebar). Grouping plants with similar water needs also reduces supplemental irrigation.

Healthy soil and an appropriate grade are another key to long-term water efficiency. If possible, existing vegetation should remain on the site. Developed root systems help stormwater return to the soil and groundwater, thus minimizing the amount of runoff and associated pollutants downstream. 

3. High Water IQ Lowers Water Waste
Hire a licensed landscape architect or a qualified site planner to focus on water-efficient landscaping and water-smart choices. For existing landscape staff, education is available on water-efficient landscape and irrigation practices through classes, seminars, and publications.

 WaterSense labels professional certification programs that emphasize water efficiency. Landscape and irrigation professionals certified under one of these labeled programs can join WaterSense as irrigation partners. Utilities and colleges also offer courses and seminars on water-efficient irrigation practices. Many local cooperative extensions and irrigation trade associations provide these resources online.

WaterSense 101

 Launched in 2006, WaterSense is an EPA-sponsored partnership program to protect the future of our nation’s water supply by promoting water-efficient products and services. WaterSense achieves these goals by labeling water-efficient products, partnering with irrigation professionals, and promoting efficient practices indoors and out.

The WaterSense label makes it easy for consumers to recognize products that save water while performing as well or better than conventional models. Third-party certifying bodies ensure that products meet EPA criteria for both water efficiency and performance by following testing and certification protocols specific to each product category. Weather-based irrigation controllers will be the first WaterSense-labeled irrigation products.

A list of WaterSense partners who provide design, installation, maintenance, and auditing is available at www.epa.gov. In addition, WaterSense has a Water Budget Tool at www.epa.gov/watersense to assist professionals in designing a climate-appropriate landscape.

4. The Whole Is Greater Than the Sum of Its Parts
An irrigation system is called a system for a reason. Efficient sprinkler heads installed on poorly laid pipes will come up short of maximum water savings. Likewise, poorly installed drip irrigation could end up using more water than traditional spray heads.

Distribution uniformity is important for conservation. Often extra water is applied because the system is distributing water in an irregular fashion. When water is applied unevenly, the system tries to keep the driest spot green, wasting water in other areas.

To avoid this problem, building professionals should specify that their irrigation systems be designed, installed, and maintained by qualified professionals who follow best practices from design through installation and maintenance.

Many plant beds don’t require spray heads traditionally used to water turf areas and can instead be watered with low-flow, low-volume irrigation, also called micro-irrigation or drip irrigation. These are usually more efficient, in part due to slow and direct water application to plant root zones, minimizing evaporation and runoff. Where traditional sprinkler heads are more appropriate, building professionals can specify more efficient products, such as multi-stream, multi-trajectory sprinkler heads that are designed to distribute water more uniformly and to resist wind drift.

5. Apply Water Only When Needed
This key point seems obvious, but in many landscapes, poor irrigation scheduling is the largest water waster. Many landscapes are watered at the same level all year, adding unnecessary water for months at a time (see chart image). Overwatering can cause more damage to plants than underwatering. It can also damage streets, curbs, other paving, and building foundations.

 The amount of water and its timing should respond to weather, soil type, plant type, landscape maturity, and other factors, such as sun and shade. An irrigation professional can create an appropriate schedule and work with landscape staff to maintain it.

Advanced irrigation scheduling technologies can assist landscape staff in creating and maintaining proper schedules. By no means do these products replace educated and experienced staff, but they can take into account many of the factors mentioned above and help apply water to the landscape only when needed.

Weather-based irrigation controllers use local weather data and landscape conditions to tailor irrigation schedules to plant needs. Soil moisture-based irrigation controllers use sensors implanted in the ground to trigger irrigation only when the root zone needs to be replenished. Rain sensors, freeze sensors, and wind sensors can be added to a system to tailor irrigation schedules on a real-time, localized basis. In the near future, the WaterSense label will appear on weather-based scheduling technologies.

6. What’s Unchecked Goes Unnoticed
Just as cars need regular tune-ups, an irrigation system needs proper service and maintenance, including frequent monitoring and a thorough audit each year or two to ensure the system is functioning. Otherwise, leaks may go unnoticed or the system may be watering the sidewalk.

Building professionals can avoid major water waste by requesting their landscape staff report and repair problems as they arise and conduct periodic maintenance. They should also check that system pressure is within manufacturer specifications. If new equipment is required, buy replacement parts that are compatible with existing equipment to ensure maximum distribution uniformity.

A qualified irrigation auditor, such as a WaterSense partner, is essential to the success of any audit. An auditor can determine if baseline efficiencies are compatible with design intent and make recommendations as necessary.

Joanna Kind is a member of the LEED Technical Advisory Group for water efficiency, an environmental scientist at Eastern Research Group, Inc., and a consultant on outdoor water efficiency to EPA’s WaterSense program.

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