In an ideal situation, the pattern can be described by a straight line on a graph showing a maximum application rate near the head and a zero rate at the outer edge of the pattern. Several factors affect the ideal pattern distribution including wind, water pressure, and water flow rate. To compensate for these distortions, a 40 to 60 percent overlap is used to achieve a uniform application. Wind causes a distortion of the water application pattern. In windy areas the greater overlap is used to resist the distortion of the application pattern.
Water pressure is a major factor in the application pattern.
As an example, note the water pattern as the irrigation system is being shut down. The uniform pattern drops back to a solid stream wetting a decreasing diameter ring as the pressure and flow go to zero. This donut is not always obvious to the observer. Too high a pressure causes misting and results in a heavier application close to the sprinkler head. A pressure gauge should be used to evaluate the system operation.