MEASUREMENT OF FLOWING WATER. 131
r the hydraulic mean depth in feet.
s the fall of surface in a unit of length.
c a coefficient covering all common losses.
Examples of Value of Coefficient in Ditches.—
In
its application to the North Bloomfield main ditch * (length 40 miles,
sectional area 23.89 square feet, grade 16 feet per mile), with its
abrupt turns and sinuous course, the value of the coefficient c, as determined, varies from 44.7 to 37.7 in accordance with the season of the year.
The
Texas Creek f branch ditch is about seven-tenths of a mile long. Its
sectional area is 13.5 feet and the grade is 20 feet per mile. The
sides are rough and the curves are sharp. With a flow of 32.8 cubic
feet per second, the ditch runs about full. The value of c =
33. In connection with this ditch there is a rectangular flume 2.67
feet wide X 2.83 feet deep, made of unplaned boards, set on a grade of
32 feet per mile. The flume has some sharp but regular curves, and the
water from the ditch runs it nearly full at these points. With the
discharge 32.8 cubic feet per second, c= 59.
On
the Milton line, from Milton to Eureka, a distance of 19.4 miles, the
sectional area of the ditch is 20.39 square feet, grade 19.2 feet per
mile for the earthwork and 32 feet per mile for flume. The line is very
irregular, having many drops and chutes. The distance from Milton to
the measuring box at Bloody Run is 29-1/2 miles. The minimum
established grade for the last 10.1 miles was 16 feet per mile, with a
sectional area for the ditch of 23.05 square feet. The coefficient c, determined
from the gauging at the measuring box, has varied from 22 in its
leakiest condition to 31, which latter can be taken as correct for the
present condition. In the succeeding 30 miles below the gauge, owing to
a better character of ground, the coefficient reaches 41.
*
Increased capacity of this ditch is limited by the pipes across Humbug
Cafion. t For details of Texas Creek ditch and flume see paper by
Hamilton Smith, Jr., ,l Transactions Am. Soc. C.E.," vol. xiii. pp. 30-31.
