Center-Pivot Application Depth and Runtime
Hours per pass, gross capacity per acre, and net depth of a center-pivot irrigation system.
Example
You enter
- System flow Q (gpm) 800
- Irrigated area (acres) 125
- Gross target depth (in) 1
- Application efficiency (%) 85
You get
- Runtime per pass 70.7
- Gross capacity per acre 6.4 gpm/ac
- Net depth applied 0.85 in
Details, formula, and sources
hours = area x depth x 452.6 / flow. An 800 gpm pivot on 125 ac applying 1 in at 85% runs 70.7 hr (~3 days). The outer spans sweep more area, so the instantaneous rate under an outer span can run off even when the daily depth is right.
hours = area_acres x target_depth_in x 452.6 / system_flow_gpm; gross_gpm_per_acre = system_flow_gpm / area_acres; net_depth_in = target_depth_in x efficiency_pct / 100.
Center-pivot application depth and runtime (USDA-NRCS center-pivot design; university extension), by name.
The acre-inch-to-gallons runtime relation is public irrigation arithmetic; the pivot design and soil intake govern the actual schedule.
Estimate. AHJ and licensed professional govern.
Field names used by the API: system_flow_gpm, area_acres, target_depth_in, efficiency_pct, hours, gross_gpm_per_acre, net_depth_in
- 452.6 factor converts acre-inches to gallons over minutes (hours = area x depth x 452.6 / gpm)irrigation arithmetic
- Outer-span runoff the outer spans sweep more area; the instantaneous rate can exceed the soil intake rate even at the correct daily depthUSDA-NRCS center-pivot design