RECTANGULAR NOTCHES. _____ Discharge per foot in width of notch = C \/ H^3 ------------------------------------------------------------------ Values of C. --------------------------------------+--------------------------- H Measured in | Feet. | Inches. ---------------+-----------+----------+-----------+--------------- | Gallons | C. ft | Gallons | C. ft Discharge in | per hour. | per min | per hour. | per min ---------------+-----------+----------+-----------+--------------- Authority. | | | | Box | 79,895 | 213.6 | 1,922 | 5.13 Cotterill | 74,296 | 198.6 | 1,787 | 4.78 Francis | 74,820 | 200.0 | 1,800 | 4.81 Mo'esworth | 80,057 | 214.0 | 1,926 | 5.15 Santo Crimp | 72,949 | 195.0 | 1,755 | 4.69 ---------------+-----------+----------+-----------+--------------- In the foregoing table Francis' short formula is used, which does not take into account the end contractions and therefore gives a slightly higher result than would otherwise be the case, and in Cotterill's formula the notch is taken as being half the width of the weir, or of the stream above the weir. If a cubic foot is taken as being equal to 6-1/4 gallons instead of 6.235 gallons, then, cubic feet per minute multiplied by 9,000 equals gallons per day. This table can be applied to ascertain the flow through the notch shown in Fig. 13 in the following way. Suppose it is required to find the discharge in cubic feet per minute when the depth of water measured in the middle of the notch is 4 in Using Santo Crimp's formula the result will be C\/H^3 = 4.69 \/4^3 = 4.69 x 8 = 37.52 cubic feet per foot in width of weir, but as the weir is only 6 in wide, we must divide this figure by 2, then 37.52/2 = 18.76 cubic feet, which is the discharge per minute. +------+ +------+ | | FIG. 13 | | | | | | | | | | | +------+ +------+ | | | | | | | | | | | | | | +------+ | | | | | | | | | +----------------------------------+ Fig. 13.-ELEVATION OF DOUBLE RECTANGULAR NOTCHED GAUGING WEIR.