Center-Pivot Percent-Timer to Depth
The number the operator turns at the panel: the end-tower percent timer, converted to applied depth. revolution = revolution_100_hr x 100 / timer_pct; depth = flow x revolution / (452.6 x area). The depth is inversely proportional to the timer - dropping it from 100% to 50% does not halve the depth, it doubles it, which irrigators get backwards constantly. An 800-gpm pivot on 125 ac with a 20-hr full-speed pass lays 0.28 in at 100% but 0.57 in at 50%. Closes the loop on center-pivot-runtime. An operating aid, not a scheduling design.
Formula and source
revolution_hr = revolution_100_hr x 100 / timer_pct; depth_in = system_flow_gpm x revolution_hr / (452.6 x area_acres); pass_days = revolution_hr / 24.
Center-pivot percent-timer to depth (USDA-NRCS center-pivot design; university extension), by name.
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