Mar. 6,1916 
Flow through Weir Notches 
1087 
Table X .—Discharges (in cubic feet per second) for triangular weir notches —Con. 
Head. 
Notch angle 28° 4'. 
Notch angle 30 
Notch angle 60 
Notch angle 90 
Feet . 
I. IO 
Inches. 
O. 809 
0. 865 
1.83 
3-15 
I. II 
. 827 
.884 
1.87 
3. 22 
I. 12 
I 3 A 
• 843 
.904 
1. 91 
3 - 30 
13 
13 A 
.864 
.924 
I. 96 
3-37 
I. 14 
i 3 tI 
.882 
•944 
2. 00 
3-44 
I -15 
I3 ff 
. 901 
.964 
2. 04 
3 * 5 2 
I. 16 
* 3 ii 
. 921 
• 985 
2. 09 
3 * 59 
I. 17 
14^ 
. 940 
1. 01 
2. 13 
3 - 67 
I. 18 
. 960 
1.03 
2. l8 
3 - 75 
I. 19 
14k 
. 980 
05 
2. 22 
3-83 
I. 20 
14 H 
I. OO 
1 07 
2. 27 
3-91 
I. 21 
14 'A 
I. 02 
1. 09 
2. 32 
3-99 
I. 22 
14^ 
I. 04 
1. 11 
2.36 
4- 07 
I. 23 
14 H 
I. 06 
1. 14 
2. 41 
4. 16 
I. 24 
14^ 
I. 08 
1. 16 
2. 46 
4. 24 
I.25 
*5 
I. II 
1. 19 
2. 51 
4 - 33 
Although weirs with triangular notches are well suited to a compara¬ 
tively wide range of discharges, they are especially well adapted for the 
measurement of small discharges and may be used to measure accu¬ 
rately quantities so small that they would not pass through trapezoidal 
or rectangular notches without adhering to the crests. The use of weirs 
with triangular notches requires slightly more fall than is required with 
trapezoidal or rectangular notches—that is, a head of 2 feet is required 
to deliver approximately 14 cubic feet per second through a 90° triangular 
notch, while the same discharge would be delivered through a 3-foot 
rectangular notch with a head of 1.31 feet, or through a 4-foot rectangu¬ 
lar notch with a head of 1.07 feet. 
Weirs with 90° notches are simpler in construction than any other 
type of weir and are the most practical type for small or medium-sized 
discharges. The approximate formula Q = 2.a t gH 2A * gives discharge 
values for 90° notches, which agree very closely with the values obtained 
with the general formula. 
