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Slope Irrigation

Slopes are great for some things, skiing, for instance, or, if you’re inclined to climb hills or mountains they are very handy. Aside from these areas, slopes can be a nuisance. Some property owners like to grade a slope and put in, say, a pool or tennis court, but some people like a little slope in their lives and may think some plants or grass would look really nice up there, too.

Now, if you don’t live in Seattle, the slope greenery will need regular watering. A person could get a hose and just manually water the area. Kids used to earn money by watering the neighbors’ plants while they cavorted at vacation destinations. However, since man left his cave and stopped chasing after wild boars with clubs and spears, he’s grown a bit lazy physically, but his mind is working overtime to develop labor saving technology.

When it comes to irrigation, man is truly ingenuous. We’ve gone to one of the experts on irrigation matters, Rain Bird, to explain the ins and outs of slope irrigation. We live to learn, and hope you'll pick up a few pointers. [The tips have been condensed for space considerations.]

  1. To reduce run-off, select an irrigation timer that controls your water applications.

    Choose an irrigation timer with at least four start times per program. Determine how long a station can be on before run-off occurs. Divide the run time necessary to meet the plant water requirements by this factor.

  2. Use master valves and flow sensing equipment as an insurance policy.

    Use a master valve to reduce the length of constantly pressurized mainline around the slope and before the zone valves. A normally closed master valve will supply a mainline with water only when a cycle is initiated from the controller. This equipment will reduce the time that a damaged sprinkler, a broken pipe, or a defective valve will have to wash away the landscape.

  3. Use reverse-flow valves to reduce problems associated with a worn diaphragm.

    A reverse flow valve will prevent water flow if the diaphragm tears, as it will fail in the “off” position.

  4. Use pressure compensating/regulating devices to get the best sprinkler coverage.

    Pressure-regulating modules can be installed on valves to adjust the operating pressure of sprinkler heads down stream to distribute water as efficiently and uniformly. Built-in regulating devices are the best option, since the optimum pressure is delivered directly to each sprinkler head.

  5. Adjust the distance between lateral lines to compensate for the slope.

    On a 2:1 slope, a properly adjusted sprinkler will throw about 80 percent of its radius above the head and 120 percent of its radius below the head. Space sprinklers consistently laterally, but the distance between bottom and middle laterals should be reduced and moved up toward the top of the slope to obtain head-to-head coverage and compensate for the true effects of the slope.

  6. Space lateral lines across the slope rather than with the slope.

    The lateral lines must follow the contours of the slope. If lateral lines are incorrectly installed from the top to the bottom of a slope, the pressure differential resulting from the elevation change could create severely uneven pressures at each of the sprinkler nozzles.

  7. Limit sprinkler heads on a valve zone to decrease potential damage.

    As you add more sprinkler heads to a zone, the size of the delivery system components and infrastructure naturally increases, meaning more water available to cause damage. Large zones are not recommended unless safeguards are in place.

  8. Limit sprinkler heads on a valve zone to increase performance.

    Tailor the irrigation system to meet the specific water requirements of the slope. Separate zones to apply water to slope sections with considerably different plant material, different exposures to sun, wind and other climatic influences. If you mix zones together, it will be hard to keep plant material healthy because one side of the slope will get too much or too little water.

  9. Place part-circle sprinklers on separate zones or use matched precipitation rate nozzle packages.

    As uniform distribution is critical for effective slope irrigation, separate part-circle sprinklers from full-circle sprinklers and adjust station run times. An easier method is to use nozzle sets specifically designed to create consistent precipitation rates, despite the various arcs and radii.

    Matched precipitation rate nozzles on the same valve system reduces the chance that your system will put down too much water with some heads and not enough from others, and help diminish the potential for severe soil erosion.

  10. Install sprinklers with check valves to contain erosion.

A check valve located at a higher elevation will contain the unpressurized water in the lateral lines after the zone valve has completed its watering cycle. Without a check valve, the elevation difference from a valve above to the sprinklers below could generate enough internal pressure to force water out of the sprinkler.

A check valve will prevent the water that remains in the pipe from draining out of the sprinklers after the valve has shut off, reducing the chance of erosion of the landscape areas around or on the slope. Look for sprinklers that have built-in check valves. This eliminates the need for a separately installed check valve under each sprinkler.

An Additional Tip from Rain Bird

On slopes with groundcover instead of turf, consider 6 or 12-inch, pop-up sprinklers rather than riser-mounted sprinklers. Pop-ups improve the visual impact and may help cut down on vandalism.

Proposed “Water Star” Program Eyes Smart Controllers

FALLS CHURCH, Va. – Smart controllers are likely to be among the first irrigation products to get water-efficient labels from a proposed water conservation awareness program, reports Tom Kimmell, executive director of the Irrigation Association.

Kimmell attended an Environmental Protection Agency stakeholder meeting to help shape a voluntary program to label products aimed at increased water efficiency. The proposed program would be similar to the EPA’s “Energy Star” program for labeling energy-efficient products.

“Water Star” seems to be the preferred name for the water-product labeling program, although it is not officially decided, Kimmell said.

The February meeting in Phoenix was to gather information about outdoor watering for the labeling program as it relates to urban landscape and irrigation products.

“I think the consensus was that labeling of irrigation and water-efficient products is something that can be done.” – Tom Kimmell, executive director of the Irrigation Association.

“I think the consensus was that labeling of irrigation and water-efficient products is something that can be done,” Kimmell explains. “Labeling irrigation products can be difficult because the efficiency of irrigation systems isn’t just dependent on products. It requires proper design, installation, maintenance and operation.” Kimmell added that nationwide certification or “labeling” of contractors could become part of the program to help consumers know which contractors are qualified to design and install efficient systems.

Smart Water Application Technology

The initial labeling initiative for outdoor watering is likely to include passive or “smart” controllers because the Irrigation Association and water purveyors have already been working on Smart Water Application Technology (SWAT).

SWAT promotes “smart” irrigation systems that use sensors or weather data to control watering rather than time-based systems, which tend to waste water. “Smart” controllers generally use evapotranspiration or soil moisture to schedule irrigation applications. Evapotranspiration controllers use weather data and information about the plants and local conditions to determine how fast plants lose water and when they need watering. By preventing over watering, smart systems help prevent unnecessary leaching of nutrients into waterways and can result in more efficient fertilizer usage. They save water without sacrificing the landscape. Smart technology has been used on public lands and in professional settings, but the technology is becoming more within the reach of the individual consumer.

Flow-Control Sprinklers

Kimmell reports the EPA labeling program could also include flow-control sprinklers. Flow-control sprinklers create a consistent output of water at any water pressure. With traditional systems, the first sprinkler on a line might over water to get enough water to the last sprinkler with the weakest pressure.

The final EPA stakeholder meeting in April in Seattle will focus on indoor products. Government agencies were the focus of an earlier stakeholder meeting.

Stakeholders Attend

More than a hundred stakeholders attended the EPA meeting in Phoenix. Representing the IA in panel discussions were Kimmell; Brian Vinchesi, IA president and president of Irrigation Consulting, Inc.; Dave Zoldoske, president-elect and director of the Center for Irrigation Technology; Lorne Haveruk, board member and president of Diamond Head Water Management Services, Inc., and Kevin Gordon of Hunter Industries, Inc.

Vinchesi, Zoldoske and Gordon helped lead a panel discussion on the role of new landscape irrigation technologies in enhancing water efficiency. Haveruk sat on a panel discussing whether design, installation and operation can be certified to achieve water-efficient irrigation.

The Irrigation Association has worked to advance water-use efficiencies since 1949. For more information, visit

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December 6, 2019, 12:46 pm PDT

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