streamflow

• What is streamflow measurement?

  It is the process of measuring the flow of water in streams.
• What are the components of streamflow?

  • Direct precipitation on the stream surface
  • Surface runoff
  • Subsurface runoff or interflow
  • Groundwater flow
• What is surface runoff?

  It is the water that flows over the ground surface into tributary channels.
• What is subsurface runoff?

  It is water that percolates through the soil and moves laterally to a stream channel.
• How is streamflow measured?

  Streamflow is measured in volume per unit time, usually in cubic feet per second (cfs) or cubic meters per second (cms).
• What is the difference between runoff and streamflow?

  Runoff is the draining of precipitation from a watershed, while streamflow is the flow rate of water in streams.
• What are the types of streams?

  • Effluent streams
  • Influent streams
  • Perennial streams
  • Intermittent streams
  • Ephemeral streams
• What are effluent streams?

  Effluent streams occur when the water table intersects the stream channel, causing water to move toward the stream.
• What are influent streams?

  Influent streams are those where water from the streams moves toward the water table.
• What defines perennial streams?

  Perennial streams have a groundwater reservoir large enough to keep the water table above the stream bottom even during droughts.
• What is an intermittent stream?

  An intermittent stream carries water most of the time but ceases to flow occasionally due to seepage and evapotranspiration.
• What is an ephemeral stream?

  An ephemeral stream carries water only during and immediately after rainfall or snowmelt.
• Why is streamflow important in hydrology?

  • It relates to water supply
  • It is crucial for flood control
  • It aids in reservoir design
  • It is important for irrigation and drainage
  • It affects water quality
• What is hydrometry?

  Hydrometry is the science and practice of water measurement.
• What are the methods of measuring streamflow?

  1. Direct methods

  • Area-Velocity Method
  • Electromagnetic Method
  • Dilution Method
  • Ultrasonic Method

  1. Indirect methods

  • Hydraulic structures (weirs, flumes)
  • Slope-area method
• What is the stage in streamflow measurement?

  Stage is the height of the water surface or stream level measured from an arbitrary datum.
• What is a rating curve?

  A rating curve is the relationship between stream stage and discharge.
• What are the advantages of stage measurement?

  • Easy to implement
  • Inexpensive
  • Continuous readings can be obtained
• What is a staff gauge?

  A staff gauge is a fixed graduated staff used to measure the elevation of the water surface.
• How does a wire gauge work?

  A wire gauge measures water surface elevation by lowering a weight to touch the water surface and measuring the height based on the reel's rotation.
• What are automatic stage recorders?

  • Automated devices for measuring and recording stage
  • Operate at specific time intervals
  • Examples include float-gauge and bubble gauge
• What is the function of a float-gauge recorder?

  A float-gauge recorder measures water stage by recording the movement of a float with changes in water level.
• How does a bubble gauge work?

  A bubble gauge measures water level by bleeding compressed air through an outlet and measuring the pressure related to the water column above it.
• What are the advantages of bubble gauges over float-gauges?

  • No need for costly stilling wells
  • Can measure large changes (up to 30m)
  • Recorder can be installed away from the sensing point
  • Less likely to be blocked or choked
• What is the stage-discharge relation?

  • Requires simultaneous measurement of stage and discharge
  • Provides a calibration graph known as the rating curve
  • Different for each stream
  • Allows estimation of discharge from stage measurements
• What is the formula for discharge in the area-velocity method?

  $Q =$$A \cdot V$
• What is the purpose of current meters?

  Current meters are devices used to measure the velocity of flow at a point in the stream's cross-section.
• How is velocity measured using floats?

  Velocity can be measured by tracking the surface velocity of the stream using floats.
• What is the relationship between surface velocity and average velocity?

  The average velocity is related to surface velocity by the equation $v =$$k \cdot v_s$, where $k$ is a reduction factor.
• What are the methods to estimate streamflow using the area-velocity method?

  1. Mean-section Method
  2. Mid-section Method
• How is total discharge calculated in the area-velocity method?

  Total discharge is calculated as $Q =$$\sum q_i$, where $q_i$ is the discharge for each subsection.
• What is the trapezoidal formula used for in the area-velocity method?

  The trapezoidal formula is used to calculate the area of each segment in the stream.
• How is mean velocity calculated in the area-velocity method?

  Mean velocity is calculated as $V =$$\frac{V_i + V_{i+1}}{2}$.
• What is the process for calculating total discharge in a stream?

  • Divide the cross-section into vertical sections
  • Measure depths and velocities
  • Calculate discharge for each segment
  • Sum the discharges to find total discharge