Question

Hydraulic engineers in the United States often use, as a unit of volume of water, the $acre-foot$,defined as the volume of wa-ter that will cover $1$ acre of land to adepth of $1$ ft.A severe thun-derstorm dumped $2.0$ in. of rain in $30$ min on a town of area $26k{m}^2$.What volume of water,in acre-feet, fell on the town?

Answer 1

The acre-foot is defined as the volume of water that will cover one acre ofland to a depth of one foot.

One acre is equal to 43650 square feet. One foot is equal to 12 inches. The thunderstorm caused2 inches of rain to fallon a town with area 45 square kilometer.

One square kilometeris equal tosquare meter. One square meter is equal tosquare feet = 10.7639square feet.

45 square kilometer is equal to $45\times {10}^6\times 10.7639$ or $484.376\times {10}^6$ square feet.

The volume of water that fell on the town is equal to $484.376\times {10}^6/43560\times \left(2/12\right)=1853.29$acrefeet.

The volume of water that fell during the thunderstorm in acre-feet is$1853.29$.