If your area hasn’t already experienced a frost this fall, tonight will likely be the night. After a couple of days of cooler temperatures and gusty winds, low temperatures are supposed to dip into the mid 20’s throughout much of the state tonight. With November just around the corner, the fall season will soon give way to winter (I think some of us thought it would never get here). Many of you will probably be winterizing your irrigation systems within the next three weeks. I wrote an article last year about the process of winterizing your irrigation system. You can access that article by clicking here. The winterization process and the freeze thaw cycles typically experienced during an Iowa winter can affect the overall performance of your irrigation system. A relatively easy way to check the efficiency of your irrigation system is by performing an irrigation audit.
An irrigation audit can be conducted for any location on the golf course (greens, tees, fairways) that receives overhead irrigation. The audit process involves recording various site characteristics and then conducting a test to determine how uniform the irrigation system is applying water to the area being tested. Information such as the sprinkler type, arc adjustment, nozzle size, operating pressure, head spacing and soil type are examples of site characteristics that are typically recorded. The uniformity is determined by placing a series of catch cans in a grid pattern across the area to be tested and then running the irrigation system for a specified amount of time.
The pictures below are from an irrigation audit I recently conducted. In the first picture you can see the catch cans placed across the green in a grid pattern. The distance between the catch devices will depend on the size of the area you are testing. We used heavy duty cups as our catch device for this audit and they were placed on 15 foot centers. Any object can be used to collect the irrigation water as long as all the objects are the same and you can measure the size of the opening of each catch device.
The irrigation system is then run for a specified amount of time and water is collected in each catch device. The amount of time the system is operated depends on the type of irrigation heads. In this audit the heads were gear driven rotors and the system was run for 10 minutes. The amount of water collected in each catch can is recorded once the cycle is complete.
Below you can see the results from this audit. The values from each catch device are used to calculate the Distribution Uniformity of the area. The DU represents how uniformly water is applied to the area and is expressed as a decimal. A DU value of 1.0 would represent complete uniformity within the area tested. For rotary sprinklers, the Irrigation Association considers DU values of 0.8 Excellent (Achievable) and 0.7 Good (Expected). Values below 0.55 are considered Poor and action should be taken.
The calculated DU for this golf green was 0.63. The obvious question now becomes what can I do to improve the overall efficiency of the system? Performing regular maintenance activities such as leveling sprinkler heads, adjusting arcs for matched precipitation rates, checking and replacing clogged or worn nozzles and drive mechanisms are all practices that will help. The results of the audit may alter you to problems that require more significant repairs such as moving sprinkler heads to appropriate spacings, adjusting water pressure (up or down), or even upgrading various system components.
Increasing the DU of your irrigation system can save your facility a significant amount of money and water over the course of the season. Uniformly applied irrigation can also lead to improved and more uniform playing conditions. The Irrigation Association offers some great resources about the auditing procedure. There is also a one and a half day seminar at the GCSAA Education Conference that provides classroom and hand-on experience of the auditing golf courses if you are interested in learning more.