area of flow in the subsection. Total discharge in the channel is the sum 

 of the discharges in the subsections (Figure H-3). 



Approximate Measurement Technique 



The discharge in a channel can be approximated using simple field tech- 

 niques. The cross-sectional area of flow can be estimated for the entire 

 cross section as the product of the top width and the average depth. The 

 mean surface velocity in the channel can be estimated by placing an object 

 which just barely floats in the flow near the center of the channel and record- 

 ing the time required to travel between two measured points. The mean velocity 

 is typically 80 to 90 percent of the surface velocity. The product of the 

 estimated mean velocity and cross-sectional area is the estimated discharge. 



REFERENCE 



Buchanan, T. J., and Somers, W. P. 1969. Discharge measurements at gaging 

 stations. Chap. A8, Book 3, Techniques of Water-Resource Investigations 

 of the United States Geological Survey, U. S. Government Printing Office, 

 Washington, D. C. 65 pp. 



153 



