Mar. 6, 1916 
Flow through Weir Notches 
1053 
He obtained the values for the coefficient and exponent by examining 
Francis's experimental data and increasing Francis's coefficient value 
somewhat arbitrarily by i per cent. He also made a few experiments, 
but stated that his formula was subject to the limitations imposed by 
Francis; consequently the extension of the range of application of the 
formula has been an excursion into unexplored territory. The notch 
designed by Cipolletti was intended to measure a minimum discharge of 
150 liters (5.3 cubic feet) per second and a maximum discharge of 300 
liters (10.6 cubic feet) per second, thus further restricting the use of the 
Cipolletti formula to notches having crest lengths of not less than 3 feet 
nor more than 8 feet. 
There is great practical need in irrigation practice for weirs with small 
notches and for measurements with small depths of water over the crests 
of the notches. It also is important to know that the discharge for¬ 
mulas are correct, as many other forms of measuring devices are com¬ 
monly calibrated by being hitched in tandem with the weir. For these 
reasons it was deemed advisable to conduct a series of experiments with 
notches having thin edges and full contractions (1) to determine whether 
the Francis and Cipolletti formulas hold for notches of the sizes ordi¬ 
narily used in irrigation practice and (2), in case the old formulas did not 
hold, to derive new formulas. 
LABORATORY EQUIPMENT AND METHODS 
The hydraulic laboratory at Fort Collins was built in 1912-13, under 
a cooperative agreement between the Office of Experiment Stations, 
United States Department of Agriculture, and the Colorado Agricul¬ 
tural Experiment Station, and is designed for research work in hydraulics, 
especially gravity flow. 1 With the exception of the building, which 
is of brick, the laboratory is constructed almost entirely of concrete 
and metal to give it rigidity, permanency, and water-tightness. All 
water faces of concrete are covered with a 3 to 1 cement-plaster coat 
three-eighths of an inch thick. Tests have shown the seepage losses 
to be negligible. The plan and a sectional elevation of the laboratory 
are shown in figure 1. The circular storage reservoir has a top diameter 
of 87 feet, side slopes of 1 to 1, and is 6 % feet deep. The headrace connect¬ 
ing it with the weir box is approximately 60 feet long, 4 feet deep, and 
6 feet wide for the first 15 feet below the head gates and then expands 
to 6 feet deep and xo feet wide at the weir box. The weir box is 20 
feet long, 10 feet wide, and 6 feet deep, and has a heavy T-iron frame 
approximately 3 feet high and 6 feet long in its bulkhead wall. This 
frame is surfaced, bored for inch bolts, and so arranged that the plates 
containing or forming the notches or orifices and other measuring 
devices requiring a vertical position can be adjusted accurately for 
experiments. The joints between the plates and the frame are made 
1 For a complete description of the hydraulic laboratory, see an earlier article by the writer (4). 
