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University of MN Extension 2 <br />Step 3: Uniformity calculations and scheduling zones <br />To calculate the precipitation rate of each <br />irrigation zone, calculate the average depth of <br />water in the catch cans for one hour of run <br />time. For example, if the average depth of our <br />20 cans was 0.75 inches and we ran the zone <br />for 30 minutes, our precipitation rate would be <br />1.5 inches per hour. For uniformity <br />calculations, take the average depth of the <br />lowest 25% of cans (in this case the five <br />lowest cans) and divide by the overall average <br />of all cans. For example, if the average of our <br />five lowest measuring cans is 0.5 inches, <br />divide 0.5 by 0.75 = 0.67 or 67%. Irrigation systems with lower than 60% uniformity <br />should be adjusted for more uniform coverage. <br />Once you have calculated the precipitation rate for each zone, you can set the <br />run times. If your goal is to apply 0.5 inches in one irrigation cycle and the <br />precipitation rate is 1.5 inches per hour, set the zone for 20 minutes. <br />MEASURE THE DEPTH OF WATER IN EACH CAN <br />For more information: <br />U of M Extension Lawn Care: www.extension.umn.edu/turfarass <br />U of M Turfgrass Science Blog: www.turf.umn.edu <br />Conducting an Irrigation Audit: www.irrigation.orq/Resources/Audit Guidelines.aspx <br />