11-01-98 | Association News
One of the most challenging aspects of designing a landscape irrigation system is selecting an application to serve the needs of the variety of plant materials-- indeed, giving the owner the lush green lawn and vibrant plant materials that he wants, while trying to be cost efficient and water-conscious at the same time.

Irrigation manufacturers used matched precipitation rates (MPRs) to ensure that nozzles (various radii and pattern) apply water at even rates. Some gear-driven sprinklers feature nozzles -- as pictured -- that offer close-in watering to help eliminate "doughnuts" and allow flexibility in sprinkler layout design. The irrigation industry is making great strides in developing spray heads for turf, ground cover and shrub applications that conserve water while ensuring healthy plant materials. In-stem pressure regulation helps reduce water runoff and meet the needs of all spray areas, regardless of changing elevation or water pressure on the site.

Among Landscape Architects, the consensus seems to be to "use as little water as possible on golf courses," by using more sprinklers with smaller radii. Golf course irrigation designs pay a great deal of attention to wind direction and separation of lush turf from native plantings or shrub areas (right). When aerating a pond that does double duty as an irrigation reservoir (left), pump manufacturers do not recommend trying to modify an existing pump system; rather, size and specify an aeration system specifically designed for the specific volume and depth of the pond in question.

The irrigation design (displayed above) produced by EDAW, Inc. consists of 4 controllers and 2 water meters. The 5 acre site utilizes 23 gallons of reclaimed water per square foot each year. In total, an average of 4.7 million gallons of water is used per year. Stream rotors are easily recognized for their "fingers of water," and are best used on medium to large lawn areas. MPRs refer to uniform delivery of water across an irrigated area. Each sprinkler's coverage covers every blade with no more, and no less, water than the next-- resulting in high-precision application and healthy turf.

In this irrigation plan for Columbia Technical Center (a 195-acre commercial/light industrial Planned Unit Development) by irrigation consultants at Beighley & Associates Inc., the common area encompasses approximately 48 acres of landscaped areas. The water source, from the city of Vancouver's domestic waterline, for the centrally controlled irrigation system is 360 GPM at 75 PSI. Common sprinkler symbols consist of a blackened-in circle, square, hexagon or triangle. The same shapes can again be used, but left open, to provide additional symbols.

The basic sprinkler pattern applies more water near the sprinkler and less and less water as you move further from the sprinkler. "Head-to-head" coverage -- when one sprinkler throws to the next -- is most commonly utilized but there may be exceptions.

Water, water everywhere and not a drop to drink... or use for that matter if irrigation design is not taken at a serious level. In the past, just plain water and a little tender-loving care used to be enough to keep turf, trees and plantings alive. However with technology on the rise and constant drought issues, there are now a multitude of irrigation options and devices offered to the water-conscious Landscape Architect-- including drip irrigation, low volume, moisture sensors, pop-up spray heads, irrigation enclosures, and backflow prevention devices...the list is endless. The population is also growing, causing a seemingly never-ending construction of residential, industrial and golf course projects. Vibrantly colored flowers and lush green lawns/turf beautify their facades, and more often than not, the nuances and technicalities of the irrigation design within these areas remains not in the mind of the average spectator-- but the Landscape Architect.

A recent survey conducted by Landscape Architect and Specifier News indicated that 53% of Landscape Architects offer in-house irrigation design services, while 27% subcontract out to irrigation consultants, and 20% rely on irrigation manufacturers for design. In one case, Principal and Owner Hal Beighley of Beighley & Associates Inc. in Portland, OR--explains that approximately 90% of his company's projects include irrigation design performed in-house. In reference to hiring outside consultants Beighley states, "I wouldn't even consider it because I feel, as a Landscape Architect, I have the most amount of knowledge of what irrigation products will do and won't do." This statement affirms that most Landscape Architects are qualified to do irrigation design...who better than the person who knows the the "ins and outs" of the plant materials that are utilized within their designs. On the other hand, the Nashville,TN-based landscape architectural firm of Hodgson and Douglas produces both in-house designs through their Landscape Architects and subcontracts out for irrigation designs. Partner James Douglas feels confident in going to outside consultants and states, "We still do irrigation designs in-house, but if we are too busy, we just subcontract out."

The differences between commercial or residential landscapes and golf course irrigation designs are--as Beighley puts it quite aptly--"like night and day." Generally, golf courses use 1,200 to 1,600 gallons of water per minute, whereas water usage on commercial landscapes run between 50-70 gallons per minute. President Lee Niles of Southern Irrigation Consultants, Inc. in San Antonio, TX explains that for a golf course it can cost up to "$800,000 to 1.5 million dollars for a new landscape system." As for landscape systems, it depends on the water intensity--prices can run around "25 cents per square foot." Associate and Irrigation Engineer Eric Montelongo of the landscape architectural firm EDAW, Inc. in Irvine, CA, believes "golf courses are driven by cost versus performance" and that the irrigation costs for the average urban project would be "75 cents to $1 a square foot."

When choosing an irrigation system, there are several methods available to Landscape Architects, including sprinkler (line voltage) irrigation, bubbler irrigation, and drip irrigation. For sprinkler irrigation, the sprinklers are patterned to fit the irregular shapes of the landscape, and spaced to complement one another. This method is suitable for plants and turf areas on moderately angled slopes. Precipitation rates range from medium to high.

Bubbler irrigation, on the other hand, involves positioning the spray heads in planting wells or gridded in shrub beds to irrigate level basins. This irrigation type may be appropriately used on shrub bed applications, but is not always suitable for slopes or turf applications due to the low operating pressure.

Since its birth in Colorado in 1913, drip irrigation seems to receive mixed reviews among Landscape Architects and irrigation designers. Drip irrigation systems--also commonly known as "trickle" or low-flow" irrigation--apply water directly onto individual plants, as opposed to sprinkler systems, which irrigate the entire surface area. This type of irrigation is often used in conjunction with sprinkler irrigation. Although turf sprinkler irrigation offers relatively low costs per irrigated area, drip irrigation can offer numerous benefits to potted plants, mulched shrub beds, and trees. Beighley uses drip irrigation very seldom and only when it comes at the request of the client. He explains, "The problem with drip is you don't realize something is wrong until it's too late. The filters must be cleaned on a regular basis and a lot of people are not willing to pay for the extra time." However, according to Montelongo, the use of drip irrigation results in "healthier plant material." He emphasizes, "Drip irrigation involves applying water directly to the soil into the plant and the result of that is you get a greater efficiency of water use." When plant materials are irrigated above ground, for example, using sprinklers, the efficiency rate, when the water is thrown in the air, is approximately 60%; the remaining 40% usually ends up on the pavement. Drip, on the other hand, is 90% efficient.

Another method of irrigation is landscape irrigation using potable water. According to Stephen W. Smith, author of "Landscape Irrigation Design and Management," most landscape irrigation systems in the United States use potable, municipal water supplies because it is readily available to most projects through the water utilities infrastructure, which is financed, constructed and maintained by others. The water user is then generally required to install, maintain and periodically test a backflow prevention device, in order to prevent any contaminated, and therefore non-potable, water from flowing backward into the potable water. This device is vital because if any contaminated water does enter the potable system, the problem can actually endanger human life because the irrigation water can be mixed or injected with chemicals, such as fertilizers, herbicides, pesticides or fungicides. President Jeff Keim of Backflow Prevention Device InnClosures advises Landscape Architects to make sure that when they select a backflow prevention device to "always require an enclosure to minimize vandal and theft problems. Also, specify one with the highest aesthetics, engineering and safety feature available."

LASN also questioned various irrigation manufacturers across the nation on what advice they would give to a Landscape Architect who is specifying an irrigation control system, and pumps and aerators. In regards to the irrigation control system, Irrigation Marketing Manager Dirk Lenie of The Toro Company states, "First verify with the client both the irrigation control requirements and capability to manage/use the system." He continues, "Select a system that meets these requirements: offers a future upgrade path, ensure that the manufacturer and their distributor will provide training, and long term after sales service support." As for pumps and aerators, Fred March, President of Oase Pumps, Inc., comments, "Use a dual system--one for aesthetics and one for water quality. This becomes critical in any remotely natural application (i.e. lake and ponds)." Heather Schwabe, Marketing Assistant of Otterbine-Barebo, Inc., adds, "Many try to adapt a nozzle assembly to an existing pump system which may not be sufficient. Size and specify an aeration system specifically designed for the precise volume and depth of the pond."

When Landscape Architects and Irrigation Consultants were asked to list the top leaders in irrigation manufacturing, nearly all named industry giants Toro, Rain Bird and Hunter Industries. Landscape Architect and Irrigation Consultant Hank Granger of Granger Associates explains that he chooses those companies because his company "specifies more of their products. Quality, the representation in the area plus the variety of products" are other factors. Beighley adds that, "We are most familiar with them and work with them on a day-to-day basis. Our local representatives also support us whenever we need help." Many respondents also indicate they enjoy working with irrigation distributors and smaller companies, because of personal attention, service and local availability.

Today, water conservation issues and irrigation design--especially in the western states of the nation--go hand-in-hand. Douglas comments, "We are trying to be more efficient by reducing the layout of heads and pressure heads. We have had no luck in using bubblers because they get clogged up as a result of the maintenance crew not upkeeping their maintenance." In addition, Montelongo, who works primarily on commercial projects, explains that there must be an awareness of the plants being selected. It is not uncommon to see twice as much water used on residences; the owners should be more conscious." He continues, "There must be an understanding of the goal of irrigation--and that is to take care of the plant material."

Irrigation design trends are becoming more technologically advanced and water efficient. Water conservation goals and complying with city ordinances; efficient, radio-communications controllers; and water efficient sprinklers are becoming more common factors in landscape irrigation projects. Niles believes that, "In the next few years, the biggest change in irrigation designing will involve effluent or reused water."

According to Montelongo, the most challenging aspect in designing an irrigation system is "selecting an application to serve the needs of the variety of plant materials" and giving the owner what he wants yet trying to be cost efficient at the same time. The last advice that he offers to Landscape Architects who are designing irrigation systems, "Check the water-use classification of plant material for consistency." lasn img

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