In Montana, both physically and legally, ground and surface waters are connected. In other words, water pumped from a well lowers groundwater levels, which in turn, impacts surface water supplies connected to that groundwater. This means that whether you are on a public water supply, or a private well, your water use can affect the flow in local streams and rivers.
These impacts are particularly noticeable during the summer months when water use is at its peak. For example, in the Gallatin Valley, more than 50 percent of total residential water usage each year is for lawns and gardens. Fortunately, there are simple steps that landowners can take to reduce water use while maintaining great looking landscapes and reducing impacts to groundwater supplies and local stream flows.
Automatic, in-ground sprinkler systems are very popular. In the Gallatin Valley, the majority of single-family homes have these systems. Irrigation systems can improve water efficiency but if not properly designed, programmed, and maintained, they use significant amounts of water.
When installing a new sprinkler system or adding to an existing system, it is worth spending some time with a sprinkler system design professional. In most cases, the reason a sprinkler system is inefficient is due to poor design that does not accurately account for plant water requirements and basic principles of water movement. An ounce of prevention is worth a pound of cure!
For instance, each valve should water a portion of landscape with similar site, slope, and soil conditions, plant material, and watering needs. Turf and non- turf areas should be watered with separate valves. Drip emitters, sprinklers, and bubblers for trees should also be on separate valves. Tree bubblers should not exceed 1.5 gallons per minute (gpm) for each device.
To avoid contamination of drinking water supplies, a backflow preventer should be installed for all sprinkler systems. If the static pounds per square inch (psi) of pressure exceeds system requirements by 15 psi, a pressure reducing valve (PRV) should also be installed. This prevents excessive evaporation loss and reduces the likelihood of leaks and breaks.
For turf areas, no single zone should mix sprinkler head types. Avoid placing rotors and sprays on the same zone. No overhead or spray sprinkler systems should be installed in strips less than eight feet wide. Small areas (i.e., 25 feet wide or less) should be watered with multi-spray, multi-trajectory (MSMT) nozzles with matching precipitation rates.
Large areas (i.e., wider than 50 feet) should be watered using rotors with a precipitation rate of at least 0.45 inches per hour for full circle (360 degree) heads. All sprinkler heads should be spaced so there is “head to head coverage” (i.e., the water arc from one head should meet the water arc of the adjacent sprinkler heads) and heads should pop up a minimum of four inches above turf areas. Drip systems are highly efficient and should be used in any landscape bed. When considering drip for turf areas, be sure to consult with a certified installer.
The system should be monitored during installation to ensure it is being installed per the plans. Make sure you obtain the “as-built” drawings of the system as it was installed. At a minimum, these drawings should show all points of connection, main and lateral line sizes and locations and static water pressure. Components like heads, backflow preventers, PRVs (pressure reduction valves), valves, zones, and controllers should also be identified. These drawings will save you valuable time and money when repairing, maintaining, upgrading or remodeling the sprinkler system.
Sprinkler systems should maximize water efficiency, only providing what plants require. For new and existing systems, installing weather-based controllers that offer multiple programs, multiple repeat and rest cycles, and a flexible calendar can offer water savings of 30 percent or more. Ideally, your controller should be able to temporarily shut down using rain, freeze, or wind sensors. Weather-based controllers allow for adjustments to watering schedules based on ET (evapotranspiration: how much water the plants need).
The best time to run your system is between 4 a.m. and 8 a.m. This reduces water loss from wind and evaporation, and provides plants adequate water to maximize photosynthesis when the sun rises. If you cannot water all zones within that window of time, earlier in the morning is preferred. Watering between 8 a.m. and 10 p.m. should be avoided.
Program the controller for multiple repeat cycles (i.e., cycle and soak) of shorter duration to reduce runoff. This is particularly important on slopes and for soils with low infiltration rates. Adjust run times based on angle of exposure to sun and wind (north, south, east, and west) and keep zones with high sun exposure separate because they will require longer run times. Zone run times should be adjusted seasonally and checked at least monthly to make sure the watering schedule accounts for the ET rate.
Regular maintenance of your irrigation system is essential. Create a zone map for ease of system inspection and controller programming. If needed, examine and clean filters. If your controller is battery operated, make sure the date and time inputs are correct and the back-up battery is functional. Adjust valves for flows identified in the manufacturer’s specifications. Adjust sprinkler heads to ensure that nozzle size, arc, radius, level, and angle of the nozzles are compatible with the slope. Immediately repair and replace broken components and pipe to design specifications in order to minimize water waste and avoid undue wear and tear on the system. Make sure any after-market retrofits are compatible with existing components.
Create and follow plans for system winterization and spring time start-up. Systems should be winterized to remove water in the lines. Avoid damage from late and early season freezes by insulating your backflow preventer. Make notes on types and locations of any repairs that will need to be done the following spring.
Following the practices outlined above can result in water savings of 30 to 50 percent or more without impacting the appearance of your turf and landscapes.
For information on how to determine precipitation rates and the performance of your sprinkler system, visit:
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