LIT194-Handbook of TII.pdf - Diamond Head Sprinkler Supply

Maximum System Capacity RequirementThe following formula is to be used to determine the gallons per minute (gpm) necessary forpeak water demand periods. While an area might survive for short periods with less water byutilizing soil moisture reserves, extended periods of drought would require the maximum systemcapacity. The formulas below (#10, #11, #12) are a guide and it should be remembered the answeris no better than the factors that go into the formula (e.g. Reference Evapotranspiration Rate, Area,Distribution Uniformity, etc.).Maximum System Capacity Requirement – GPM per Hydrozone(s)This formula is used to determine the maximum water required, in GPM, from the source basedon the hydrozone’s characteristics.GPM =0.0104 x Et o x Area x K cDU x Hrs. AvailableVariable Value Ranges:GPM = gallons per minute requiredEto= peak daily evapotranspiration for the worst case scenario in inchesArea = area to be irrigated in square feetKc= Crop Coefficient - use 1.0 if actual crop coefficient is not knownDU= distribution uniformity or irrigation efficiencyHrs. Available = hours available for irrigation each day in the worst case0.0104 = constant for conversion of area, flow and inches per day, etc. intocommon unitsExample:A park has been designed with 450,000 sq. ft. of turf, and all areas must be irrigated between10 p.m. and 6 a.m. The crop coefficient is 60% (0.6) with an average peak evapotranspiration rateof 0.35 inches per day. The system distribution uniformity has been estimated to be 65%. What willbe the maximum gpm required for the park?GPM = 0.0104 x 0.35 x 450,000 x 0.600.65 x 8GPM = 189®Handbook of Technical Irrigation Information15