Slope Irrigation Techniques
Effective slope irrigation is a mixture of good upfront planning and proper installation technique. If done properly it will not only make for a happy customer you'll also avoid costly call backs.
June 28, 2021
Original article by Rain Bird Corporation
Meeting plant material water requirements with irrigation systems can be a challenging task under normal circumstances. When slope plantings are involved applying water efficiently and effectively can be extremely challenging. Too little water and nothing will grow too much water and you've got erosion problems. If this sounds familiar read on.
From controller programming to selecting the correct sprinkler several tactics can be utilized to help you deal with the ups and downs of slope irrigation.
Look for controllers that have multiple start times or built in features like cycle and soak.
Start by surveying your customer’s landscape and work out how long a sprinkler station can water an area before runoff occurs, as well as how much water that station needs for vegetation to thrive. Take the runtime needed and divide it between multiple start times throughout the day to reduce the length of time the station runs at a time. This way, controllers like Rain Bird’s ESP-ME can be set to split run times into safe chunks of time to preserve the land and minimize erosion while meeting vegetation needs. Controllers with advanced features like Cycle+SoakTM will split runtimes automatically.
Site plans often don’t show how much ground slopes cover accurately, which can cause confusion and mistakes. Be sure to account for the slope’s range as you lay down lateral lines. For reference, a properly adjusted sprinkler throws around 80% of its radius above the head, and 120% below the head on a 2:1 slope (Rain Bird). Compensate for the effects of the slope by reducing the space between the middle and bottom lateral lines; these should be moved closer towards the top of the slope.
Additionally, lateral lines should follow the slope’s contours. Space the lines across the slope instead of with it. If installed incorrectly in a top-down formation, the pressure differential from the elevation change can generate uneven pressures at the sprinklers which can cause uneven water distribution. Higher pressures can build at the bottom of the slope and can damage the system.
As an insurance policy, use a master valve, pressure regulators, and flow sensing equipment.
Master valves are especially important for sloped irrigation as it acts as a back-up to shut off water supply. Install this at the water source to reduce the pressure on the mainline. The controller can open and close the master valve, and it’s on when zones are watering the landscape. When closed, the master valve will ensure there is no running water through the system. If using flow sensing equipment, the master valve will shut of the system and close if there are issues like the mainline bursting, leaks in the lines, malfunctioning sprinklers, or other causes of damaging erosion.
Install a high-flow/low-flow pressure device with a flow sensor at the source also. Ensure the flow capacity is the same as the largest flow demand. This flow sensing equipment can detect excessively high flows, normally caused by issues like a pipe break. If installed properly, the use of this with a master valve will significantly reduce damage to the landscape.
Pressure regulators will ensure landscaping will receive the best sprinkler coverage. Built-in pressure compensating or regulating devices such as the 1800-PRS and 5000+PRS provide the best option since the optimum operating pressure is delivered directly to each sprinkler head. Nozzles that run at the optimum pressure are more efficient, and often sprinklers that run at non-uniform and non-optimum pressures can cause flora to deteriorate.
Protect landscaping with reverse-flow valves and check valves.
Reverse flow valves will prevent water from free flowing through the pipes if there is a problem or break. Without this, there could be challenging erosion issues from continuously running water through a broken system.
Ensure you install sprinklers with check valves as another safeguard. Check valves contain the water in the lateral lines when the zone’s watering cycle is complete. If there aren’t check valves in place, the slope could cause enough pressure to force water from the nozzles, causing erosion and runoff issues. Choosing sprinkler heads with integrated check valves eliminates the need to install check valves separately.
Driplines can also be installed for controlled release watering with minimal erosion.
Consider valve zones carefully.
Limit sprinkler heads on a valve zone to increase performance and minimize risk of damage. Ensure the amount of sprinkler heads and pressure is correct for each hydrozone’s watering needs and climatic exposures. Too many sprinkler heads in one zone means more water flow during system failure and depending on zone needs could mean overwatering.
Additionally, to ensure uniform water distribution, separate full-circle and part-circle sprinklers and adjust station run times as needed. Consider using nozzle sets that create consistent precipitation rates by design despite different arc and radii ranges to reduce different water pressures and flow across a zone, therefore reducing erosion risk. Because many slopes are planted with ground cover instead of turf, consider installing highly efficient XFS-CV Check Valve Dripline which offers controlled release watering to help eliminate runoff and encourage healthy root growth. Not only will the landscape dripline improve the visual impact of the site, it isn't visible, and may help cut down on vandalism.
*This article first appeared on the Rain Bird Resource Library.