Streamflow Measurement

Transcription

1 Streamflow Measurement Second edition Reginald W. Herschy Partner, CNS Scientific & Engineering Services Reading, UK E & FN SPON An Imprint of Chapman & Hall London Glasgow Weinheim New York Tokyo - Melbourne Madras

2 Contents Preface Acknowledgements xiii xv Chapter 1 Introduction Field measurements Cost effectiveness International standards in stream gauging Summary of methods Selection of method 7 11 Chapter 2 The velocity-area method of streamflow measurement General Spacing of verticals Computation of current meter measurements Measurement of velocity Current meters Rating of current meters Considerations in current meter design Care of current meters Procedure for current meter measurement of discharge Chapter 3 Measurement of stage General The reference gauge Water level recorders Optical shaft encoders Solid-state recorders 122

3 viii Contents 3.6 Stilling wells and intakes Instrument house Telemetering systems Chapter 4 The stage-discharge relation General The station control The simple stage-discharge curve The logarithmic method Examples of logarithmic stage-discharge curves Rating table Sensitivity Semi-logarithmic graph paper Polynomial curve fitting Chapter 5 Special problems in streamflow measurement Depth corrections for sounding line and weight Oblique flow Stilling well lag and draw-down Rapidly changing discharge Shifting control Extrapolation of rating curves Overflow Current meter measurements from ice cover Streamflow in arid regions Safety measures in streamflow measurement Chapter 6 Measurement by floats General Cross-sections Floats Placing of floats Position fixing Determination of mean velocity Computation of discharge Example The rising air float technique Float gauging using aircraft

4 Contents Chapter 7 The slope-area method of streamflow measurement 7.1 General 7.2 Chezy and Manning equations 7.3 The energy equation 7.4 Calculation of velocity head 7.5 Estimation of Manning's n and Chezy's C 7.6 Calculation of discharge 7.7 Selection of reach 7.8 Examples Chapter 8 The stage-fall-discharge method of streamflow measurement 8.1 General 8.2 Categories of stage-fall-discharge ratings Chapter 9 Weirs and flumes 9.1 General 9.2 Principles and theory 9.3 Measurement of head 9.4 Check calibration in the field 9.5 Types of measuring structure 9.6 Non-modular (drowned) flow 9.7 Summary of the range of discharge for standard weirs and flumes 9.8 Summary of uncertainties in the coefficients of discharge 9.9 Non-standard weirs 9.10 Orifices and sluices Chapter 10 Dilution gauging 10.1 General 10.2 Principle 10.3 Tracers 10.4 Selection of measuring reach 10.5 Procedure 10.6 Comparison between the two dilution methods Chapter 11 The moving boat method of streamflow measurement 11.1 General ix

5 x Contents 11.2 Theory 11.3 Limitations 11.4 Determination of the vertical velocity coefficient 11.5 Selection and preparation of measuring section 11.6 Equipment 11.7 Functions of the crew 11.8 Examples 11.9 Automated moving boat method Chapter 12 The ultrasonic method of streamflow measurement 12.1 General 12.2 Principle 12.3 Theory 12.4 Site selection 12.5 Operating frequency 12.6 Minimum depth requirement 12.7 Crossed paths 12.8 Depth measurement 12.9 Reflector system Responder system System design Advantages, limitations and accuracy The broad-band acoustic Doppler current profiler (ADCP) Chapter 13 The electromagnetic method of streamflow measurement 13.1 General 13.2 Principle 13.3 Theory 13.4 Site selection 13.5 Design and construction Chapter 14 Accuracy 14.1 Introduction 14.2 Standard deviation 14.3 Nature of errors 14.4 Theory of errors 14.5 The error equation 14.6 Values of uncertainties 14.7 Examples in the calculation of uncertainties

6 Contents xi 14.8 The uncertainty in the stage-discharge relation Estimation of length of record required at a streamflow station Uncertainties in individual methods Chapter 15 Hydrometric data processing General Chart recorders Solid-state recorders Computer data processing Data transmission Data quality control Ultrasonic and electromagnetic streamflow stations Wastewater treatment works and waterworks flows Archive files Data retrieval Publication of flow data Chapter 16 Flow in pipes Closed conduit flowmeters Discharge through unmetered pipes Appendix: Conversion factors 516 Index 518