CHAPTER 10  CURRENT METERS
The velocityarea principle is used to compute discharge from currentmeter data. Total discharge is determined by summation of partial discharges. A partial discharge is the product of an average point or vertical line velocity and its meaningfully associated partial area, expressed as:
The total discharge is then:
The simple average, the midsection method, and Simpson's parabolic rule applied to both the depth and average vertical line velocity values will be discussed using figure 1016. This figure shows: (a) where the boundary is broken up into inflecting straight line sections and (b) where the boundary is smoothly curved.


The measured and computed variables are as follows:
q = the discharge in cubic feet per second (ft^{3}/s)
for a partial area
Q = total discharge
= the mean velocity associated
with the partial area
a = partial area of total cross section
L_{1}, L_{2},... L_{n}=
distance to vertical measurement locations in feet from an initial point
to vertical station
L = the distance in feet
between consecutive vertical measurement stations
,,...
= the respective mean velocities in feet per second at vertical measurement
stations
D_{1}, D_{2},... D_{n}=
the water depths in feet at verticals
n = the number of verticals related to the partial area