Streamflow

• What is streamflow defined as?


  The volume of water passing a specified point in a given interval of time
• How can streamflow from a watershed be measured at a gauging station?


  By measuring the stage at the station and converting it to discharge using a rating curve
• What are the methods of determining streamflow?


  • Estimating flow by determining water velocity through a cross-sectional area
  • Routing flow through a measurement device for direct measurement
  • Using appropriate measurements and mathematical models for indirect determination
• What is the purpose of current meters in measuring velocity?


  To measure the velocity of water flow
• What are the components of current meters?


  • Shaft rotating vertically or horizontally
  • Tail vanes to keep it in the stream
  • Weight to keep the cable vertical
• How is streamflow generally measured?


  By observing stage or elevation above a specified datum and relating it to discharge via a rating curve
• What does the stage of a river refer to?


  The height of the water surface above an established reference plane
• Why do measurement accuracy requirements differ for various purposes?


  Because different applications may require different levels of precision
• Why do wide shallow cross sections need more accurate water level measurements than narrow deep sections?


  Because the flow dynamics in wide shallow areas can be more variable
• What is the purpose of stage-discharge relation curves?


  • To determine stage-discharge relations
  • To estimate discharge at a particular moment using a rating curve
• Why is establishing a relationship between stage and discharge (rating curve) common practice?


  Because determining discharge every time is laborious and time-consuming
• What does the formula for the rating curve represent?


  It relates discharge \( Q \) to stage \( h \) and coefficients \( a \) and \( b \)
• What is the formula for discharge in terms of stage readings?


  $Q =$$a(h - h_0)^b$
• What does plotting \( Q \) against \( (h - h_0) \) on double logarithmic paper produce?


  A straight line
• What is the process for determining coefficients \( a \) and \( b \) in the rating curve?


  • Use linear regression on the transformed data
  • Calculate \( \log a \) and \( b \) from the data
• What is the value of \( h_0 \) in the rating curve example?


  0.5
• What is the linear regression equation derived from the rating curve example?


  $y =$$1.4742x +$$0.9698$
• What does the transformed data in the rating curve example consist of?


  • Original data of stage \( H \) and discharge \( Q \)
  • Arranged data for analysis
  • Logarithmic transformation of \( (h - h_0) \) and \( Q \)