The precipitation rate is a ratio of the volume of water applied to a area over time.
NOTES:
To estimate the PR in sprinkler zone add the total expected flow (from manufacturers tables) and the area of the zone. To estimate the PR in an orchard with sprinklers use the expected flow of one sprinkler and the area covered (spacing).
To use the PR for determining runtime divide the desired application in inches by the PR. For example to apply .5" of water with a PR of .25"/hr you would run the system for 2 hours. Note that this does not account for uniformity (or lack of). Since systems are not 100% uniform you will need to increase the actual runtime.
Tools on this site are intended for education purposes only and are not intended for commercial use. For more information contact Michael Spiess at California State University, Chico.