4.2 Streamflow

• What is an ideal property of tracers used in the dilution method?

  Non-toxic
• Why should tracers not be very expensive?

  To ensure cost-effectiveness
• Why should tracers be detectable at small concentrations?

  To accurately measure flow rates
• What should tracers not get absorbed by?

  Sediments or vegetation
• Why should tracers be lost by evaporation?

  To prevent accumulation in the environment
• What should tracers not chemically react with?

  Channel boundary or channelbeds
• What are the two types of dye addition methods in the dilution method?

  • Dye Slug
  • Continuous Addition
• How is concentration measured in the dilution method?

  In stream over time
• What is the electromagnetic method used for?

  Flow measurement
• What is the ultrasonic method primarily used for?


  Measuring average velocity
• What are indirect methods in flow measurement?

  • Use flow discharge and depths relationship
  • Two categories:

  1. Flow measuring structures
  2. Slope area method
• What are examples of flow measuring structures?

  • Notches
  • Weirs
  • Flumes
  • Sluice gates
• What limits the use of flow measuring structures?

  Head, debris, sediment load, backwater effects
• What does Q represent in flow measurement?

  Discharge
• What is the range of Manning’s roughness coefficient (n)?

  0.01 to 0.75
• What does R represent in the Manning equation?

  The hydraulic radius
• How is the hydraulic radius (R) calculated?

  Area divided by wetted perimeter
• What does S represent in the Manning equation?

  Head loss per unit length
• What does hL represent in the energy equation?

  Total head loss
• What are the components of head loss (hL)?

  eddy loss and frictional loss
• What is the stage discharge relationship also known as?

  • Rating curve
  • Plots discharge against stages
• What does the control in stage discharge relationship represent?

  Combined effects of channel and flow parameters
• What is permanent control in stage discharge relationship?

  Constant Q-Q relationship over time
• What is shifting control in stage discharge relationship?

  1. Q relationship changes with time
• What factors can change the control in stage discharge relationship?

  • Weed growth
  • Dredging
  • Channel encroachment
  • Aggradation or degradation
  • Variable backwater effects
  • Unsteady flow effects