The handbook of Technical irrigaTion informaTion - Hunter Industries

Handbook of Technical Irrigation InformationCoefficient of UniformitySchedulingThis formula is used to measure the variability of water distribution over a given area. It is calculated by using aseries of catchments and comparing the average (mean) catchment and the deviation from that average. This formulawas developed by J.E. Christiansen.C u = 100 (1.0 - ∑x )mnWhere:C u = Uniformity Coefficientx = the deviation of individual observations or catchments∑x = the sum of the deviations of individual observations from the mean value, mm = mean value of all observations in the distributionn = number of observations in the distribution100 = constant for conversion to percentExample:16Sprinkler HeadCatchment (number)24 5783Catchment #Catchment Quantity(ml)Deviation From Mean(mean = 46.75 ml)1 48 1.252 51 4.253 44 2.754 41 5.755 45 1.756 44 2.757 50 3.258 51 4.25Total 26.00Note: catchment may be expressed in any convenient unit ( i.e. milliliters, ounces, etc.), as long as all catchments are measured in the same units.In a landscape area, eight catchments are placed between sprinklers and the above observations recorded. What isthe Coefficient of Uniformity?C u = 100 ( 1.0 – 26.00 )46.75 x 8C u = 93.020