Triangular Notch Weirs

     

Formula: Q = ( C )  ( 4/15 )  ( L )  ( H )  
Where: Q = flow of water in cu. ft. per sec.
L = width of notch in ft. at distance H above apex
H = head of water above apex of notch in ft.
C = constant (varies w/ condition), .57 used
a = no less than 3/4 L
  for a 90° notch the formula is
  Q = 2.536 H 5/2
  for a 60° notch the formula is
  Q = 1.408 H 5/2
Head
(H)
(in.)		 Flow in Gallons
(per min.)
90° notch 60° notch
1/4 0.07 0.04
1/2 0.42 0.24
3/4 1.10 0.62
 1 2.19 1.27
 1 1/4
3.83 2.21
 1 1/2
6.05 3.49
 1 3/4
8.89 5.13
 2  
12.4 7.16
 2 1/4
16.7 9.62
 2 1/2
21.7 12.5
 2 3/4
27.5 15.9
 3  
34.2 19.7
 3 1/4
41.8 24.1
 3 1/2
50.3 29.0
 3 3/4
59.7 34.5
 4  
70.2 40.5
 4 1/4
81.7 47.2
 4 1/2
94.2 54.4
 4 3/4
108 62.3
 5  
123 70.8
 5 1/4
139 80.0
 5 1/2
156 59.9
 5 3/4
17 100
 6  
193 112
 6 1/4
214 124
 6 1/2
236 136
 6 3/4
260 150
 7  
284 164