USE OF CONCRETE PIPE IN IRRIGATION. 
33 
Several years ago, a large number of experiments were conducted 
by V. M. Cone of this bureau at the hydraulic laboratory at Fort 
Collins, Colo., on the flow of water through weir notches. 4 
In figure 11 is outlined the inside dimensions of a standard weir 
box to measure water within 1 per cent of accuracy in accordance 
with the different volumes specified in Table 1. In Table 2 is given 
in cubic feet per second the discharge through rectangular weirs from 
1 to 4 feet in length and for varying heads. 
Table 3 gives the percentage of error which occurs when changes 
from the standard form are introduced. Thus the effect of side con- 
tractions (C in figure 11) is seen in the increase in error of a 1-foot 
weir and a 6-inch head from less than 1 per cent to 4 per cent when 
the distance of the sides from the end of the crest is reduced from 
2 feet to 6 inches as shown in figure 12. 
Fig. 11. — Standard 18-inch weir based on dimensions given in table. 
Table 1. — Weir-box dimensions for rectangular notch weirs. 
[ All dimensions in feet. The letters at the heads of the columns in this table refer to figure 11.] 
RECTANGULAR WEIRS. 
Flow (second-feet). 
|to3.. 
2to5.. 
4to8.. 
6to 14. 
10 to 22 
H. 
L. 
A. 
Length 
K. 
Length 
B. 
E.o 
C. 
D. 
Hook- 
Maxi- 
Length 
of box 
of box 
Total 
Total 
End of 
Crest 
mum 
of weir 
above 
below 
width 
depth 
crest 
to 
dis- 
tance. 
head. 
orest. 
weir 
weir 
of box. 
of box. 
to side. 
bottom. 
notch. 
notch. 
1.0 
1 
6 
2 
5J- 
3i 
2J 
2 
4 
1.1 
n 
7 
3 
7 
4 
2f 
2| 
4£ 
1.2 
2 
8 
4 
8| 
% 
3J 
2f 
5 
1.3 
3 
9 
5 
12 
5 
4h 
31 
51 
1.5 
4 
10 
6 
14 
5* 
5 
H 
6 
G.c 
Hook- 
gauge 
dis- 
tance. 
4 For further information the reader is referred to Farmers' Bulletin 813 on the Con- 
struction and Use of Farm Weirs, by V. M. Cone. 
a This distance allows for about * foot freeboard above highest water levelin weir box. 
t> Equals distance from crest upstream to gauge. 
c Equals distance from end of crest over to gauge. 
