YSI SonTek RiverSurveyor, System Manual

Page: 75 / 194

SonTek/YSI Inc
RiverSurveyor System Manual (May 1, 2007)
63
Section 5. Principles of Discharge Measurement
This section describes the principals and methods of calculating the total discharge of water
through the measured cross-section. The following topics are covered in Section 5.
•
Discharge Calculations – How do I calculate discharge?
•
Velocity Profile Extrapolation – How do I calculate current velocities in unmeasured areas?
5.1. Discharge Calculations
The following topics are covered in this section:
•
How does RiverSurveyor calculate discharge?
•
Are there limitations to the discharge calculation?
•
How do I calculate total discharge for the section using RiverSurveyor?
5.1.1. How does RiverSurveyor calculate discharge?
The RiverSurveyor program measures water motion in three-dimensions (X/North, Y/East,
Z/Up) throughout each profile of the water column as it travels from one side of the river to the
other. As described earlier in (§
3.2.2
),
Figure 3-8
shows a general representation of the current
profiling and discharge measurement principles. As the profile data is received, RiverSurveyor
also collects data on ADP position, distance traveled, and water depth. This information is used
to calculate the net flux of water or discharge through the cross-section.
Figure 5-1
shows how the RiverSurveyor ADP measures discharge as it transects across the river
from one bank to the other. This figure demonstrates the following:
•
Discharge is measured as the boat transects from riverbank to riverbank.
•
RiverSurveyor can measure discharge over a change in course and speed.
•
RiverSurveyor adjusts for vessel speed and direction.
Figure 5-1. Velocity calculation