Abstract: Accurate methods to model the precipitation rate, water delivery spatial distribution, and distribution uniformity for irrigation systems for landscapes are described. A relatively small set of test data is fitted to empirical and physics-based formulas. This permits the extrapolation of test data for an irrigation system with sprinklers being used with any arbitrary specification of operational and environmental variables. The environmental variables are the pressure at the sprinkler head, sprinkler model and nozzle choice, range of arc operation, throw adjustment, head tilt, run time, and spatial position. The environmental variables are the wind profile and three-dimensional terrain topology. The; invention predicts the surface distributions and the three dimension spatial distributions.