Proper spacing of sprinklers to achieve uniform application of water is clearly a goal of system design. In general, more water falls close to the sprinkler head and less and less is applied as one moves away from the sprinkler head. 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.