In the united states, volume of irrigation water is usually expressed in acre-feet. one acre-foot is a volume of water sufficient to cover 1 acre of land to a depth of 1 ft (640 acres = 1 mi2, 1 mi = 5280 ft). the principal lake in the california water project is lake oroville, whose water storage capacity is listed as 3.54 x 106 acre-feet. express the volume of lake oroville in (a) cubic feet, (b) cubic meters, and (c) us gallons.