SPRINKMOD - pressure and discharge simulation model for pressurized irrigation systems. 2. Case study

A computer model, SPRINKMOD, was tested with field data collected from a co mplex sprinkler irrigation system in operation. The original data collected were adjusted in order to calibrate the model for the irrigation system. F ive modifications were made in the original data so that the model sensitiv ity could be evaluated. The model predicted the system operating point with less than 1% error, after some adjustments in the data. The relative mean standard error was 4.1% for the upstream pressure heads and 2.1% for the do wnstream pressure heads of all later als analyzed together. Measurement of pressure and discharge at pump stations along with a reasonable estimate of leakage appears to be essential for simulation of old systems. Adjustments made to pipe wall thickness and pipe roughness were not as important as th e adjustments made to the lateral valves closure in getting SPRINKMOD to si mulate pressure heads that were close to the measured values. For long late rals, like center pivot laterals, a variable local loss coefficient for flo w past a riser outlet worked better than a fixed value of 0.3.