Finding Solutions to Landscape Irrigation Runoff

Sept. 1, 2002
According to a June 2001 report by three California water districts and private consultants, residential water demand in the state accounts for 54% of the total urban water demand (Irvine Ranch Water District, 2001). Of this percentage, more than half is for landscape irrigation purposes.A 2000 Gallup poll revealed that Americans spent $17.4 billion in landscape-related services in 1999. In other words, people have a lot invested in lawns, gardens, and trees, and the logical conclusion is that society will protect that investment. One of the most basic needs of turf, trees, and other plant materials, of course, is water–a need that is made more complex by drought conditions, booming populations, and water-supply infrastructures designed many years ago that are failing to live up to current demands. With municipalities across the country facing water rationing, the green industry also might face negative consequences of limited water supplies.The greatest challenge, it appears, has not so much to do with applying adequate moisture to plant life as it does with teaching the public–especially people with irrigation systems–what efficient watering really entails. A report by Brent Mecham, landscape water management and conservation specialist with the Northern Colorado Water Conservancy District (NCWCD), estimates that property owners who water their lawns by hand overuse water by 10% on average; by comparison, those with automatic sprinkler systems overwater by 30-40% during the growing season.Just like healthy sources of potable water, landscaping is a component that makes a community more “livable.” When it comes down to an either/or choice, though, water always will win. The question is: Can the green industry thrive when water becomes scarce? How willing are landscape owners to embrace water-wise practices? And what about contamination of surface waters from landscape-specific pollutants? The solutions lie within irrigation efficiency. New technologies will play a key role for certain, but irrigation system owners also will need to become enlightened. Irrigation’s Contribution to Nonpoint-Source PollutionSociety’s affinity for landscapes has led to chemical solutions for almost any problem that might affect that layer of greenness. Homeowners and professional groundskeepers use a multitude of fertilizers and pesticides to keep boring and chewing insects, brown grass, and yellowing leaves at bay. Another methodology, chemigation, applies these materials simultaneously with irrigation water. Such contaminants can be conveyed to waterways not only during a storm event, but also in dry weather when the landscape is negligently overwatered. Nitrogen and phosphorus from fertilization can result in excessive algae growth in water bodies, and solid materials such as grass clippings and leaves also release unwanted nutrients into water systems. Pesticides, pet feces, and other contaminants common to a landscaped setting can affect stream biology negatively if carried beyond the landscape by runoff. “Most of the nonpoint-source pollution is not really caused by irrigation per se,” explains Mecham. “It’s caused by everything else that we do to the landscape. And then the water becomes the carrier or the vehicle for moving that.” Through Environmental Protection Agency Section 319—funded projects with which he’s been involved, Mecham has found that once these chemicals actually have come into contact with the soil, there’s very little movement thereafter. Runoff becomes an issue when the materials themselves, or contaminated grass clippings, end up on hard surfaces, such as sidewalks or driveways, or when people blatantly overirrigate in an attempt to revive that seemingly indestructible brown spot on their lawn.It should be noted that proper fertilization actually could play a role in reducing runoff. Studies by NCWCD from 1993 through 1999 show that an average of 0.43 lb. of nitrates per acre leached through the soil profile of one study site from 1993 to 1995. The soil at the site was a heavy, silty clay loam; the turfgrass was primarily three varieties of improved Kentucky bluegrass. In 1996, no fertilizer was applied, but the lawn’s deterioration led to 4.2 lb. of leached nitrates per acre.A new project was started in 1997 to look at nitrate leaching from five fertilizer sources and as a result of overwatering. Soil disturbance associated with the study resulted in initial nitrate leaching of between 20 and 37 lb./ac. Once the site was well established, though, that figure dropped to 1.9 lb./ac. And 1998 and 1999 saw nitrate leaching of approximately 1 lb./ac.Enforcement of the Clean Water Act is leading to strict regional rules in such places as San Diego County, CA, which, according to Irvine Ranch Water District’s Water Conservation Manager Thomas Ash, has the most stringent requirements to date. These rules address common homeowner activities, such as hosing down a driveway or washing a car, and they also deal with landscape runoff. “The proposed fines could be $10,000 per day imposed by the regional EPA, aimed at cities, counties, and landowners,” Ash warns. “It is very conceivable that a landscaper could be the target of the landowner’s fine.”The City of Albuquerque, NM, also has a strong enforcement program in place. Jean Witherspoon, the city’s water conservation officer, states, “Irrigation runoff is a problem addressed through the water conservation program’s water-waste enforcement program. Basically any irrigation runoff that goes into the public right of way, whether streets, storm drains, et cetera, is prohibited. We enforce through three ‘water cops,’ who videotape the violation and assess a fee. The fees range from $20 for the first violation to $1,000 for the ninth and up.”Water AuditsTo remedy the effects of overspraying and in response to increased pressures on water supplies, many North American communities are turning to irrigation water audits–either on a voluntary or mandated basis–as a means of monitoring landscape water usage and ensuring the most efficient use of irrigation water. Providing leadership in equipping irrigation consultants and local government representatives to conduct effective assessments is the Irrigation Association (IA), which has certified hundreds of landscape irrigation auditors. “In regard to the green industry,” explains Lorne Haveruk, president of Diamond Head Water Management Services in Toronto, ON, “a water assessment gives us the background information on the site’s soils, plants, exposures to Mother Nature, slopes, low areas, system type, installation, and much more hard data. It tells us how well a system is working–or in most cases, how poorly–where the problem areas are, and–if [the auditor is] experienced enough from performing this type of work for many years–what to do with the results to get the system to water the site better using less water.”A water audit is constructed around three types of data: (1) a water-use history for the site being audited, (2) the landscape area, and (3) evapotranspiration (ET) data from a local weather station. With this information in hand, an auditor can get a reasonable estimate of the amount of water a site should be using. The next step in the audit involves a close inspection of the system. Ash explains that an auditor will look closely at valve performance and pressure. He or she also will note leaks, breaks, or clogged heads. Flow rates will be tested, and the auditor will ensure that controllers are working properly. If sprinkler heads are made by different manufacturers, this will be noted, as different products have varying outputs. Catch cans will be placed at key locations in the landscape to determine the relative coverage pattern. Some auditors might generate a computer model of coverage to determine how the system translates to the ideal. These steps can equip a water agency with the knowledge to make wiser water management decisions in the future. Points out Mecham, who teaches various courses on behalf of the IA, including the organization’s irrigation auditor course, “Fundamentally, a person will be able to learn two important things. One is what the true precipitation rate of the sprinkling system is. The second thing will be to learn how well it distributes water, or the distribution uniformity.”Irrigation Best Management Practices, published in April 2002 by the IA, describes field performance audits that check systems for: compliance with state and local requirements pertaining to such measurements as minimum precipitation rate and lower quarter distribution uniformity,presence of water management devices,ability to meet water demands of plants without excessive watering.Audits are encouraged in many communities as the first step in managing irrigation water. In some cities, audits are mandated. “The Clark County School District [CCSD] in southern Nevada has been requiring performance audits on new sites for over four years now,” notes Joseph Fortier, president of Mojave Water Management in Las Vegas. “CCSD is one of the fastest-growing school districts in the US. For several years now and still continuing, they had anywhere from eight to 12 new schools a year being built. Most of the irrigation systems were inefficient from design issues and construction. CCSD, with aid from the Southern Nevada Water Authority [SNWA] Conservation Department, developed standards for performance audits. The irrigation system would have to meet certain distribution uniformities on the overhead irrigation systems before any planting was done. Information from the performance audit was then used to program their central irrigation control system.” Fortier, a former SNWA employee who helped CCSD develop its performance audits, reports that since this school district mandated the auditing, its savings are an estimated 10-15% in both water and maintenance costs.In Bellevue, WA, commercial development plans for sites larger than 5,000 ft.2 first must be approved on the basis of the site’s ability to score well on a water audit. Obviously the actual water-use reduction that results from an audit will depend on the size of the landscape and how closely the end user follows auditor recommendations. “Minimum savings to date from the sites we have worked on have been 25% with a maximum of 72% savings for a 24-acre site,” reports Haveruk, “resulting in substantial savings on their water bill, enough to pay for the audit five times over.” He adds, “We have performed over 100 audits in the past seven years with varied results. Golf and commercial have a fairly short payback period. The residential sector is the only sector where the cost is not easily recovered.”Witherspoon also reports varied results with Albuquerque’s free water-audits program. “Both the audits and water-waste enforcement have achieved reductions with some customers; our water cops try to assist the customer in finding solutions to the runoff problem. Some have come down a lot. However, others either don’t implement any of the audit recommendations or just gravel a few inches closer to the street to hinder runoff. So it’s a mixed bag of results. We would say, however, that at least a cursory audit is one of the first steps in better managing landscape water, and therefore eliminating runoff. We also encourage rainwater harvesting, though at a fairly low level, which helps reduce runoff.”One perceived weakness of irrigation water audits is that they typically focus only on the irrigation systems themselves. Landscape efficiency, however, is dependent on many other variables, from plant materials to fertilization requirements to soil structures. If the end result is to be a system that’s as efficient as possible, auditors will want to note each and every landscape feature that is relevant to water usage. Observation of soil characteristics, for example, will be important, as will slope aspects and plant species. Each of these will provide some piece of the whole in terms of a landscape’s irrigation requirements and will be beneficial in establishing a watering schedule. Ash notes that such a broad view of audits has an added benefit to the green industry in that it adds another layer of service that contractors can provide their clientele.New TechnologiesAccording to Joe Berg, water-use efficiency programs manager for California’s Municipal Water District of Orange County, traditional approaches to conservation in residential and commercial irrigation systems, while being somewhat successful, have fallen short in terms of sustained water-use reductions. Water auditing and educational programming are beneficial in that they give the end user an ideal to strive for, but it doesn’t mean that all the necessary steps will be taken over the course of several years. It doesn’t mean, for instance, that the homeowner will adhere strictly to the watering schedule set forth as a result of the audit.“When we’ve taken a look at water savings associated with the audits,” relates Berg, “there is an initial savings, but the savings is not maintained over time, in general. That’s where we get back to what our need is, and that is to generate quantifiable and reliable savings over time.”A few technological advances that pertain to irrigation systems have been successful in bringing the lessons of the audits into real-world landscapes. One potential solution has been to take the responsibility of irrigation system scheduling away from landowners and automate it instead. For the past seven or eight years, says Berg, one method of scheduling automation has been computer-controlled irrigation systems, and performance-based grant funding has been used to distribute this technology to a few homeowners’ associations and other entities in California. Challenges remain within the single-family home sector, however, and solutions in this arena must be less cost-prohibitive.“We have come across another new technology,” Berg continues, “and that is an automated irrigation controller that communicates directly with a weather station.” WeatherTRAK is the device to which he refers, and it’s based on a system that transmits local weather data, via satellite, to the controller. The data are then processed by the controller to optimize water times. Aqua Conserve, WeatherSet, and Weathermatic are examples of other ET controllers on the market, but in a 2001 study in California’s Irvine community, explains Berg, the WeatherTRAK was chosen for two reasons: It uses real data from a weather station and it allows for multiple start times.
In the study, the WeatherTRAK controller was installed in 40 homes. Educational postcards also were provided to study participants on a monthly basis, encouraging adjustments, making start-time recommendations, and so forth. Again, states Berg, the study revealed that the educational program did result in initial–though unsustained–savings. The automated controller, on the other hand, meant steady savings of 37 gal./day per 1,200 ft.2 of landscaped area. If one acknowledges that the 40 subject homes already had something of a water conservation ethic before the study, Berg estimates that the use of automated scheduling across the broader community will result in savings of 57 gal./day per 1,200 ft.2 of landscaped area. Currently underway, the second phase of the project deals more specifically with nonpoint-source pollution. Says Berg, “When we were doing that study, we were becoming much, much more aware of watershed and runoff issues. And we saw that there was a pretty high level of customer satisfaction with that controller as well. We started to think that if we’re saving that much water, there has to be a correlating reduction in runoff.”According to Berg, the residential runoff reduction study is focusing on five neighborhoods, selected because of similar site conditions and isolated storm drains that convey wet- and dry-weather runoff into San Diego Creek. Three of these neighborhoods are controls with no intervention. A fourth is receiving education on irrigation system maintenance, system scheduling, and environmentally sensitive landscape maintenance practices. The fifth neighborhood also is receiving this educational component, but the WeatherTRAK controller is being installed as well.Within the respective storm drains, monitoring equipment has been established to measure flow rates and to test for bacteria, pesticides, and fertilizers. Though the study is still in its early stages, Berg reports that initial observations confirm the theory that the automated controller contributes to runoff reductions.What started as a $160,000 study has grown considerably as entities such as the Southern California Coastal Water Research Project, the California Department of Pesticide Regulation, the California Water Resources Control Board, and the CALFED Bay-Delta Program have gotten involved. These organizations, says Berg, had questions about landscape runoff to which they needed answers, so it has been relatively easy to piggyback them onto the study.Mecham also has worked with ET controllers and finds them to be effective water conservation tools. He, however, views them as more useful in a larger landscape situation, such as with an apartment complex, than for a single-family home. In the latter case, he advocates soil moisture sensors.Although ET demand might vary widely across any lawn because of microclimates, management with soil moisture sensors is based on the actual amount of water in the soil. A product such as the WaterMark or WaterWatcher is placed in a reference spot on a lawn, and all the sprinkling zones are adjusted for specific run times. If the sensor indicates that the soil moisture is less than optimal, then irrigation proceeds.Mecham also recommends that multiple start times be used with the soil sensors to maximize effectiveness. For example, instead of one 20-minute run time, a system instead would be set for four five-minute runs. If, after the first two runs, the sensors report sufficient soil moisture, then the final two runs won’t occur, thereby halving water use in that particular circumstance.Haveruk lists rain sensors, freeze sensors, and wind-and-rain sensors as additional technological tools that can help improve irrigation efficiency. A More Natural ApproachOutside the realm of irrigation, property owners and contractors can take other steps to significantly reduce nonpoint-source pollution from landscapes. Integrated pest management is a philosophy that looks at all viable solutions to insect problems, rather than at chemicals alone. Biological and cultural controls might be effective in many situations, such as with the use of Bacillus thuringiensis to thwart a host of landscape pests.Fertilization can be addressed through the promotion of organic, slow-release fertilizers or grass recycling. Studies have shown, for instance, that grass clippings left on a lawn can provide 15% of that lawn’s nitrogen needs.Native plant landscaping is favored by some for the simple reason that native grasses, trees, and flowers will be better acclimated to a site’s weather extremes, thereby lessening the need for watering between rainfalls. Such practices are promoted, in varying degrees, by state and local governments across the US and by cooperative extension services.Urban areas, while not as prone to agricultural runoff situations, do experience a great many of the same types of chemicals because of landscaping. And because these features are so vital to communities, a blanket recommendation of “turn off the water” isn’t applicable. Rather, the green industry and water agencies will find themselves working closer than ever to implement guidelines that protect both water systems and plantings.

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