How to size an irrigation ditch with Manning's equation
Trapezoidal section geometry, roughness values, a worked 4.8 cfs example, and the velocity and freeboard checks that matter.
Guides
Irrigation design guides
Plain-language walkthroughs of the same equations FieldFlowCAD uses, each with a worked example you can check by hand.
Irrigation pipe sizing with Hazen-Williams
Friction loss per 1,000 feet, the 5 ft/s velocity rule, and why 450 gpm wants 8-inch pipe instead of 6-inch.
How much water a headgate passes: the orifice equation
Gate opening, head difference, and the 0.61 discharge coefficient, with a worked 4.2 cfs example.
cfs, gpm, acre-feet, and miner's inches
The conversion factors every irrigator needs, including how the miner's inch changes from state to state.
Planning estimate, not a stamped design. These are steady-state equations. Real accuracy depends on surveyed elevations, current channel and pipe condition, calibrated gate ratings, and pump curves. Verify in the field and get qualified engineering review before final construction or official operation.
Skip the hand math
FieldFlowCAD runs these checks from your drawing and flags velocity, pressure, grade, and capacity problems as you draw.