Hydrological Services – HydroTablet
25-Feb-15 Issue 1.00
Page 22 of 22
©Hydrological Services P/L
HS reserve the right to modify this document at any time
Mid Section Method
(From Australian Standard AS3778.3.1 ISO 748)
The cross section is again regarded as being made up of a number of segments, however in the
mid section method each segment is bounded by the midpoint of two verticals.
The discharge of each segment is calculated as :
Discharge = Mean velocity x Depth of x Mean Width
of Segment of Vertical
Vertical between Verticals
q
1
= v1 x d1 x (b0+b1)/2
q
2
= v2 x d2 x (b1+b2)/2
q
3
= v3 x d3 x (b2+b3)/2 etc….
where
Mean Width = sum of widths to / 2
Between Verticals adjacent verticals
= (b2 + b3) / 2
The total discharge is obtained by adding the discharge from each segment.
q
(total)
= q
1
+ q
2
+ q
3
+ ………