28 Colorado Experiment Station 
UNITS OF MEASURE 
The Cubic Foot per Second, called second-foot, is a unit of 
measure for flowing water. When a stream discharges 1 cubic 
foot of water in one second, there is a second-foot flow. 
The Acre-Foot, is a unit of measure for standing water, and 
is that volume which will cover one acre one foot deep. An acre- 
inch is one-twelfth of an acre-foot, or the volume which will cover 
one acre to a depth of one inch. 
The Miner’s Inch is unsatisfactory, and rapidly losing favor 
as a unit for measuring water, because it is not a definite quantity. 
It varies with the conditions under which it is used, and is therefore 
being replaced by the second-foot. 
TABLE OF HYDRAULIC EQUIVALENTS 
One cubic foot equal 7.48 gallons, or approximately 7^ 
gallons. 
One cubic foot of water weighs approximately 62 pounds. 
One cubic foot per second equals 448.83 gallons per minute, or 
approximately 450' gallons per minute. 
One cubic foot per second flowing for 1 hour, equals approx- 
mately 1 acre-inch. 
One cubic foot per second, flowing for 12 hours, equals approx- 
imately 1 acre-foot. 
One cubic-foot per second, flowing for 24 hours, equals approx- 
imately 2 acre-feet. 
One acre-foot equals 43,560 cubic feet, equals 325,851 gallons. 
One million cubic feet equals 22.95 acre-feet. 
In Colorado it has been generally assumed that 1 Miner’s inch 
(Statutory inch) equals 1-38.4 of one cubic foot per second. 
