By Catherine A. Ruhl and Michael R. Simpson
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2005-5004ONLINE ONLY
Sacramento, California 2005
Prepared in cooperation with the
Interagency Ecological Program
Complete accessible text of report (2.8 MB PDF)
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Computation of a discharge time-series in a tidally affected area is a two-step process. First, the cross-sectional area is computed on the basis of measured water levels and the mean cross-sectional velocity is computed on the basis of the measured index velocity. Then discharge is calculated as the product of the area and mean velocity. Daily mean discharge is computed as the daily average of the low-pass filtered discharge. The Sacramento-San Joaquin River Delta and San Francisco Bay, California, is an area that is strongly influenced by the tides, and therefore is used as an example of how this methodology is used.
Purpose and Scope
Principles of Operation
Ultrasonic Velocity Meters
Acoustic Doppler Velocity Meters
Calculating Area on the Basis of Stage
Calculating Mean Velocity on the Basis of the Index Velocity
Calculating Daily Flow
Appendix A. Sample Computation of the Cross-Sectional Area Relationship
Appendix B. Sample Computation of the Mean Velocity
Appendix C. Sample Discharge Calculation
Appendix D. Calculation of Daily Discharge
Appendix E. High-Quality Data and Examples of Common Mistakes
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