184 CALIFORNIA FRUITS: HOW TO GROW THEM 



error in measuring small quantities is not great enough to be taken 

 into consideration. By converting the results of measurements in 

 miner's inches to gallons, cubic feet, or some other familiar unit, it 

 may be determined how long it will take the stream to fill a reservoir 

 or cover a given field with the necessary depth of water. This unit 

 is readily convertible into cubic feet or gallons or acre-inches of water, 

 according to the time the water flows. 



The following data will be helpful in computations: One miner's 

 inch, as described above, equals 0.1496 gallons per second, 8.976 gal- 

 lons per minute, 538.56 gallons per hour, 12,925.44 gallons per day; 

 0.02 cubic foot per second, 1.2 cubic feet per minute, 72 cubic feet per 

 hour. One acre-inch of water (that is, 1 inch in depth over an acre 

 of surface) equals 27,152 gallons, or 3,630 cubic feet, and 1 miner's 

 inch will supply this quantity in about 50.4 hours. Thus a simple 

 calculation shows that a little stream of 5 miner's inches will supply 

 enough water to cover an acre 2.3 inches deep in about 23 hours a 

 fair amount for one irrigation of soil of average character if it has 

 not been allowed to become too dry before the application. In fact this 

 is an average amount actually used for an irrigation of shallow-rooted 

 plants like most field and garden crops. 



Weir Measurement. The term "weir" is not always understood 

 by those who use it. The term can properly be used only for structures 

 designed to allow the water to flow over the crest with a considerable 

 fall on the down stream side. There are a large number of forms of 

 weirs, taking their names from the shape of the weir notch, or the 

 form of crest. The triangular weir has a V-shaped notch. The 

 rectangular weir has a horizontal crest with vertical sides. Both of 

 these forms of weir are good, when used by the expert irrigator or 

 engineer who understands the principles and factors which enter into 

 their calculations. In order to avoid the variable factors which enter 

 into the calculations for the flow of water over weirs, Cipoletti invented 

 the form of weir which has taken his name and which is in general 

 use throughout the irrigated sections of the world. 



The Cipoletti Weir. The Cipoletti Weir has a thin horizontal 

 crest, the sides of the weir notch sloping back from the vertical at an 

 angle equal to one inch in horizontal for every four inches in vertical. 

 This, for each additional inch in depth the weir notch widens on each 

 side one-fourth of an inch, or a total addition of width of one-half 

 inch. A weir having a length of crest of one foot, and designed to be 

 eight inches in depth, will have a top width of notch of 16 inches. 



When the weir box is placed, care should be taken to have the 

 bottom of the notch or crest, level. An ordinary carpenter's spirit 

 level may be used for this purpose. When the crest is horizontal, 

 one end of the spirit level is placed on the center of the crest, and 

 when level the other end will mark the point for the zero of the weir 

 gauge. In rough work a nail may be driven part way into the side of 

 the box, the top of the nail being level with the crest of the weir. A 

 thin plate of brass is to be preferred to a nail. In other cases gauges 

 are inserted on the sides of the flumes and properly marked in tenths 



