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Show TERMS USED IN MEASURING THE FLOW OF STREAMS Tbe volume of water flowing in a stream, called the '"run-off," or "discharge," "dis-charge," Is expressed in various terms, which,- however, may be divided into two groups those representing rate1 of flow and those representing actual! quantity of water. The rate of flow Is eenerallv exoressed as "second- foot," an abbreviation for cubic feet per second, the unit used for measuring measur-ing flowing water, as "gallons per minute," the unit used in connection with pumping and city water supply; : as "miner's inch," the unit used by miners and irrigators for measuring water that passes through an orifice 1 inch square under a head that varies locally; and as "second-feet per square mile," the unit used to represent the average number of cubic feet of water flowing per second from each square mile of area drained, on the assumption assump-tion that the run-off 1 distributed uniformly uni-formly both as regards time and area. The actual quantity of water Is expressed ex-pressed by the terms "run-off In Inches," Inch-es," "acre-feet" and "million gallons." "Run-off in Inches" expresses the depth to which the drainage area would be covered if all the water flowing flow-ing from It In a given period were conserved con-served and uniformly distributed on the surface, It Is used for Comparing nm-f.ff with rainfall. "Acre foot," which Is sused commonly In connection connec-tion with storage for irrigation, is the quantity of water required to cover an acre to the depth of 1 foot that Is. cubic feet. In the Territory of Hawaii the unit most commonly used in measuring the flow of water is "million gallons." Tills unit Is used not only to indicate a rate of flow ("million gallons per day") but an actual quantity of water stored in a reservoir. U. S. Geological Survey, Department of the Interior. : |