A drainage system for a 40 acre field is designed to remove 3/8 inch of standing water from the entire field in 24 hours.

What flow rate (gpm) must the drainage system achieve to meet the design specification?

2 answers

volume of water 40 acre * 3/8 " = 40 acre * 1/16 ft = 40*43560/16 ft^3 = 108900 ft^3

1 gal = 231 in^3 = 231/1728 = .13368 ft^3

so, our field is covered by 814632 gal of water

to drain that in 24 hours requires a rate of 814632/24 gal/hr = 33943 gal/hr = 565.72 gal/min
oops

3/8 " is not 1/16 ft.

make that fix and adjust the final figure by the right factor.