Sports fields are often the focal point of a facility and take the most irrigation per square foot to maintain. Because you want to keep fields in premium condition, there are fewer options for water conservation than with the typical landscape turf. Here are six simple adjustments that can save water without compromising turf quality.
Tip #1—Know The System
The first step in improving irrigation efficiency is getting to know the system. For schedule planning, know what type of area each control valve is watering and the precipitation rate. Make a list of each valve and the zone conditions. Is it a full circle or part circle? Is it a sideline zone or a centerfield zone? Is it full sun or partial shade? This information will help determine how much water is needed.
To determine runtimes, you will also need the precipitation rates for each zone. There are several ways to determine these. The most direct way is to use catch cans or rain gauges to measure sprinkler output. This can be done by a certified irrigation auditor in the area, or you can do it yourself. Many sprinkler manufacturer and irrigation distributor websites provide a step-by-step process for conducting an audit and determining precipitation rates.
Precipitation rates are not equal throughout a zone. The closer the lowest precipitation rate is to the highest, the more efficient is the system. When maintaining quality sports turf, you will always have to water to keep the driest spot green. Conducting an irrigation audit will help make adjustments to provide more water to dry spots and potentially reduce overall water use.
Tip #2—Know The Weather
In tip one, you determined how much water a system is capable of putting down. Next, estimate how much water is needed. There are a half-dozen ways to measure or estimate turf-water requirements, ranging from site-specific weather stations to soil-moisture sensors to referencing historical weather records. It can be difficult trying to directly calculate exact water usage. The most important approach is to pay attention to the weather and how it affects water use and turf quality. When it rains, turn off the system. When temperatures are higher than normal for consecutive days, water can be supplied for additional minutes on zones.
At a minimum, irrigation schedules should be adjusted on a monthly basis. If the grass is green and the irrigation schedule hasn’t been adjusted in a few months, you are probably over-watering. There are many irrigation controllers on the market that can automatically adjust for weather, and it's always a good idea to have a rain sensor. It is important to keep a recorded history of runtimes. An irrigation manager should keep a spreadsheet of the irrigation schedule and notes on weather and turf conditions. Tracking runtimes with corresponding weather and turf-condition notes will reveal patterns that will help increase future irrigation efficiency. Historical data will also reveal the maximum and minimum conditions that fields can withstand.
Tip #3—Put Down Roots
Deep turf roots, which are especially important in keeping sports fields in prime condition, are a main goal of all turf managers. Deep roots also allow the turf to maximize the amount of water available in the soil. When putting together an irrigation schedule, note the maximum length of time between irrigation cycles. Longer runtimes on fewer days of the week is one way irrigation can promote deeper root growth.
Tip #4—Check The Pressure
At what pressure does the system run? Sports fields with large commercial-grade rotor systems require a minimum of 55 psi, but 70 to 80 psi is recommended. Low pressure causes short throws and disrupts distribution patterns. High pressure causes misting that lets water dissipate into the atmosphere. Sprinkler pressure can be measured in two ways. Purchasing a peto tube and inserting it directly into a sprinkler nozzle is a simple approach. A slightly more time-consuming but more accurate reading requires digging up a sprinkler and putting a threaded pressure gauge onto the swing joint.
Some irrigators think pressure is out of their control, but there are a few ways to optimize system pressures.
Low pressure is the more common and more difficult issue to manage. Extremely low pressure may require a pumping system, but if it’s only slightly below the desired pressure, there are ways to optimize a system to gain an extra 5 psi at no additional cost. Check the programming to make sure you are not running too many zones concurrently. Watering concurrently due to limited time windows can’t be helped in some cases. To lower pressure loss during necessary concurrent watering, try to pair up zones that will balance the flow. To lower pressure loss in the mainline, try to pair up zones that will balance the flow. Pair a zone with a large flow with a zone with a smaller flow. For a single-leg mainline, pair a valve near the front of the system with a valve at the end of the line. For a looped mainline, pair valves on opposite sides of the loops. Doing this will minimize the pipe velocity in the mainline and lower friction loss.
Another common pressure problem with sports fields is the presence of a zone of shorter throw radius heads on the same mainline as large rotors. For example, on a baseball field there is probably a midrange or low-angle rotor irrigating the area behind home plate. Check the manufacturer’s recommended pressure on these heads. They should be running at 45-50 psi, which is much lower than that used in the outfield. Most remote-control valves can be fitted with an inexpensive and easy-to-install pressure regulator. Every valve with short radius heads should have one of these regulators to prevent misting.
Tip #5—Don't Touch That Screw
If at all possible, let all sprinklers run at full radius length. Using the set screw to reduce the radius on a sprinkler can disrupt the distribution patterns and lead to dry spots in unexpected locations. It may mean moving a sprinkler or two, but sprinklers always work better at full throw.
Tip #6—Maintain Control
Did you select the current irrigation controller, or was it there when you started? If you inherited a sprinkler controller, you might not know its capabilities. Do some research on your clock and see what “smart” abilities it has. Does it have an input to add a rain sensor? Can global adjustments be done to bump runtimes up or down? Can the controller be connected to a phone line or Ethernet to call for weather data and automatically adjust accordingly?
If there are multiple controllers, contact the manufacturer representatives to see if a controller is capable of being connected to a central control system. If the budget will allow for irrigation improvements, an irrigation-controller upgrade is typically the best bang for your buck in improving irrigation efficiency. The most import element when selecting a new or replacement controller is purchasing one that will be used to its full extent. If a smart controller’s advanced features will not be used, then don’t pay extra money for a more complicated system. The extra functions will only get in the way. In order to track the water budget closely, spend a fair amount of time comparing and pricing features. In recent years, many of the mid-range controller models have added water budget features that were previously available only on expensive central controls.
Springing for a handheld remote control is not only a great convenience for maintenance but also for water efficiency. If you are really pushing the minimum runtime limits or watering less frequently, a dry spot could be stressed into yellowing. If you have a remote, that zone can be quickly irrigated for 10 minutes for immediate relief before you take the time to reevaluate the schedule.
Natural-turf sports fields are one of the most used and appreciated features of any park and recreation facility. By utilizing technological advancements and implementing some simple operational modifications to an irrigation system, turf managers can provide a beautiful playing field yearlong while supporting environmental sustainability by conserving water whenever possible.
Zach Temple, PE, CID, Lloyd Consulting Group, LLC, Civil & Sports Engineering Direct: 602.904.5861