One acre-foot of water (the amount of water covering 1 acre to a depth of 1 foot) equals 326,000 gallons or 43,560 cubic feet of water, and weighs 2.7 million pounds. One cubic mile of water equals 1.1 trillion gallons, 147.2 billion cubic feet, or 3.38 million acre-feet, and weighs 9.2 trillion pounds (4.6 billion tons). Rate of flow (in a stream) Â· Water flowing at the steady rate of 1 gallon per minute is equivalent to: 1,440 gallons per day; 0.00223 cubic foot per second; 192.7 cubic feet per day;