STREAM-FLOW 63 



the permanency of the bed and the fluctuations of the surface, 

 which govern the depth. 



Gauging stations should be located at places where the record 

 of flow is to be made. Bridge locations are preferable, as from 

 them the measurements can be easily made, with the least expense. 

 If the channel conditions are not satisfactory at such points it is 

 necessary to use boats or erect a cable station, Fig. 21 showing a 



:J 



FIG. 22. Typical Gauging Station for Bridge Measurement. 



typical station used by the U. S. Geological Survey. The location 

 should also be preferable where the channel is straight and without 

 cross-currents, both above and below the station, and the bed 

 should be as free from obstructions as possible. 



The methods by which the measurements are made are in 

 general those in common use by the U. S. Survey. An arbitrary 

 number of points are laid off perpendicular to the thread of the 

 stream, Fig. 22. They are known as measuring points and divide 

 the gauging section into strips. The area for each strip is cal- 



