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Lab-2 Definitions

* Discharge
is the volume per unit time that passes any point in a stream. Direct measurement of discharge is not possible, but must be calculated from velocity and cross-sectional area of the stream, i.e. from the Discharge Equation
\begin{displaymath}
\underbrace{Q \left(\mbox{$\rm\frac{L^3}{t}$}\right)}_{\rm...
...} \cdot
\underbrace{A (\rm L^2)}_{\rm Cross-Sectional Area}
\end{displaymath} (3.1)

* Velocity
is the rate of water movement (Fig. 3.5), but doesn't specify how much (volume of) water is moving. The volume rate is needed to determine flooding, etc.
* Cross-sectional Area
is the area on a vertical plane cutting the stream (Fig. 3.2)
* Stage
is the elevation of the river above its bed, i.e. water depth

You've had direct experience with discharge when using a garden hose with a nozzle. For a given faucet setting (constant input discharge) water shoots farther out of the end of the hose (has higher velocity) when a the nozzle is narrowed (cross-sectional area is reduced). Velocity varies along a stream because of changes in cross-sectional area, but discharge varies only if there is addition or removal of water (e.g. tributaries, evaporation, etc.)


next up previous contents
Next: Measuring Cross-Sectional Area Up: Lab2 Background Previous: Lab2 Background
GEOS 3110 Professor's Notes, Summer 2003
Dr. T. Brikowski, UTD