CHAPTER 10 - CURRENT METERS

13. Computing Discharge

The velocity-area principle is used to compute discharge from current-meter 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:

equation

The total discharge is then:

equation

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 10-16. This figure shows: (a) where the boundary is broken up into inflecting straight line sections and (b) where the boundary is smoothly curved.

figure
Figure 10-16a -- Calculation of discharge using the midsection method.

figure
Figure 10-16b -- Calculation of discharge using Simpson's parabolic rule method.

The measured and computed variables are as follows: