Imperial Valley press., 1908-04-04
NOTES FROM TAT REPORT
System of Gaueing Gives Only Alp proximate Volume and Will Have to Be More Accurate Eventually-in- formation Useful to New Settlers.

tity Of water applled 10 the lanu IS stated in acre-feet One cubic foot for 24 hours equals S6.4O0 cubic feet, which so nearly equals 2 acre-feet (S7,120 cubic feet) or $1 worth of water at 50 cents per acre-foot, that records kept in cubic feet per second per day and decimals equal dollars and cents for the charge. Reckoned in inches the charge is 2 cents per inch per "A hours. The water delivered to the mutual companies is measured at the points of delivery by overpour or pres sure measurements or by previously rated fumes. The posts in the struc- lures on the large canals interfere with accuracy in measurement, and in the case of an overpour measurement the weir crest given by Pinch fash boards with battered edges is at wide variance with the theoretically perfect edge to which the weir formula ap- plies. The present measurements are therefore hardly more than approxi- mate, and both the canal company and the mutual companies realize the need of more accurate ones at these very important points. Cement structures of the best class are to be installed at all points of delivery, and recording instruments will be used.
 Water delivered by mutual water company to its shareholders is regu- lated by delivery box and gate. The same type of box is used by all the companies. The box Ur Hume Is feet long and feet wide inside. The gate is placed near the middle and is ad- iusted to allow the desired amount of water to pass under it. The wings at both ends extend into the ditch bank at right angles to the box and sheet piling is placed below the floor at both the upper and lower ends. The wings being perpendicular 70 the direc- tion of the current instead of at di- verging angles, a whirl is produced just below the lower end of the box 
 which sometimes washes away the ditch banks Much of this action of the water would be overcome by mak ing the wings diverge ~t an obtuse angle.
 The boxes constitute the measuring as we'll as the regulating devices. h. structions are given to Zanjeros re- garding the method of setting the gates to deliver any amount of water and the methods of recording the measurements. It is considered that the measurements can be made to come under one of three classes, desig- mated as submerged opcnrng," open ing with free discharge and lover pour with free discharge. Most of the measurements are made with the submerged opening. In this case the gate is raised slightly and the water passes under it and over a dashboard placed across the bottom of the box. The two ends of the rectangular ori- flee thus made are formed by the strips on the sides of the box which form grooves for the gate to slide in. This does not give the exact conditions for subm erged oriflce for which the tables used in the calcula- tion of discharges were computed, but it is an approximation. The tables used in all the computations of the discharge by the companies are speci- fled in their rules and regulations as those given by a recognized authority on civil engineering. There must be a head over the top of the opening, both above and below the gate.
 When there is a head over the top of the opening above the gate only and the surface of the tail water is low enough to allow a free fall of water from the opening, the measure ment comes under opening with free discharge" In this case there is a contraction of the jet at the top and bottom, but the contraction of the jet at the ends of the opening is insuffic- lent and undetermined on account of the strips on the box.
 Tn the overpour with free discharge