Design tips

Use a variable frequency drive (VFD) pump. VFD pumps adjust pump motor speed based on the demand of the irrigation zones that are running. Not only can this save water, but will also save on electricity.

Pay strict attention to zoning the irrigation system (how the system is sectioned or divided) for these reasons:

Fields with specific areas that incur heavier use should be zoned accordingly. For example, the centers of football, soccer or lacrosse fields typically endure more wear and tear. When it’s time to re-seed or re-sod these areas, having them on a separate zone allows you to water them as needed and eliminates unnecessary watering of the perimeter.
Sunny and shady areas should be zoned separately so you can apply more or less water to each respective area. If there are sunny areas combined with shady areas in the same zone, many sports turf managers will water according to the needs of the sunny areas, which then results in overwatering the shaded ones.
Low-lying areas should also be zoned separately to minimize or eliminate run-off that can create boggy conditions in those areas.

Design using head-to-head coverage. Head-to-head coverage (overlapping the spray from a sprinkler head with the spray from the sprinkler head next to it) maximizes irrigation efficiency. The higher the efficiency, the less time it’s required to run the irrigation system to produce the desired results. 

Use sprinklers with the same precipitation rates within each zone. “Precipitation rate” refers to the amount of water sprays or rotors discharge in inches per hour. Always have sprinklers with the same precipitation rates running together on the same zones for an even application of water over the entire zone. When sprinklers with different precipitation rates are combined on the same zone, some areas of the zone will be overwatered and others will be too dry.


Other keys to efficiency

Regulate water pressure. High water pressure causes water to emit from sprays and rotors as fog or mist, often evaporating or drifting away in the wind and leading to longer run times. Every additional 5 pounds of water pressure (5 psi) over the sprinkler’s optimum operating pressure causes each head to use 6-8 percent more water—an amount that can really add up over time. Pressure-regulating valves and swing joints can remedy this situation, as well as sprays and rotors with in-stem pressure regulation.  
Check nozzle efficiency. Distribution uniformity, or “DU,” is the industry measurement of nozzle efficiency shown as a percentage or decimal.  The higher your system’s distribution uniformity, the less time it will have to run to achieve the desired results. You can determine your DU by conducting an irrigation audit on your own using a catch-can method, or you can have a third party perform the audit, such as the Center for Irrigation Technology or your sprinkler manufacturer. 
Schedule wisely. Evapotranspiration, or “ET,” measures the rate that plants lose water through evaporation and transpiration. ET is calculated based on temperature, humidity, solar radiation, wind speed and rainfall. ET rates are typically lowest early in the morning, so water applied during that time is less likely to evaporate due to solar radiation. Wind speeds also tend to be lower in the early morning hours than at other times of the day, making it more likely for your irrigation water to land where it should and further improving system efficiency.
Consider ET-based control. Using an ET-based control system can reduce irrigation frequency by as much as 30-50%. These systems gather local weather data to calculate a daily ET rate. This information then determines whether the system should run on any given day or whether zone/station run times should be adjusted. Even if your current controller is not ET-based, it’s a relatively simple upgrade that can save a tremendous amount of water over time.

Chris Dimmick is Rain Bird’s area specification manager for the Southeast region.