Streamflow I

• Which part of the hydrologic cycle can be measured accurately?

  Streamflow
• Streamflow is measured in units of discharge
• The measurement of discharge in a stream is a key aspect of Hydrometry.
• Match the streamflow measurement categories with their methods:

  Direct determination ↔️ Area-velocity method

  Indirect determination ↔️ Weirs and flumes
• What is the simplest method of stage measurement?

  Staff gauge
• A staff gauge may be vertical or inclined with permanent markings.
• In a wire gauge, a weight is lowered by a reel to touch the water surface
• Which type of stage recorder is the most common?

  Float-gauge recorder
• Stilling wells are used in float-type stage recorder installations to protect the float.
• In a bubble gauge, compressed air is bled out through an outlet at the bottom of the river
• What does a pressure gauge measure in a bubble gauge?

  Gas pressure
• Stage data is often presented in the form of a plot called a stage hydrograph
• Which device is most commonly used for accurate measurement of stream velocity?

  Current meter
• Robert Hooke invented a propeller-type current meter in 1663.
• Match the types of current meters with their characteristics:

  Vertical-axis meters ↔️ Conical cups around a vertical axis

  Horizontal-axis meters ↔️ Propeller mounted on a shaft
• In a rough turbulent flow, the velocity distribution is described using shear velocity and sand-grain roughness
• What depth is used for velocity measurement in shallow streams in the single-point method?

  0.6 times the depth
• In rivers with flood flows, only surface velocity is measured to determine average velocity.
• In flood-prone rivers, what depth below the surface is the surface velocity measured?

  0.5 m
• The average velocity v is obtained by using a reduction factor K as v = Kvs, where K lies in the range of 0.85 to 0.95.
• Wading is a velocity measurement method applicable only to small streams with shallow depth.
• What is used as an observation platform in rivers flowing through narrow gorges with well-defined channels?

  Cableway
• Bridges are hydraulically the best locations for gauging stations due to their stability.

  False
• Railway and road bridges are frequently employed as gauging stations due to their accessibility and transportation
• What is the most satisfactory aid for velocity measurement in wide rivers?

  Boats
• Match the term with its description:

  Sounding weights ↔️ Lead weights used to stabilize current meters

  Hangar bar ↔️ Connects sounding weights to current meters

  Streamlined shape ↔️ Reduces water resistance on weights
• What is the formula for estimating the minimum weight of sounding weights?

  $W =$$50vd$
• The velocity measurement by floats uses the relation S/t, where S is the distance travelled and t is the time taken.
• The float method of measuring velocities is primitive but still applicable in special circumstances.
• What is a simple float moving on the stream surface called?

  Surface float
• Special floats with part of the body underwater are used to directly measure the average velocity in the vertical.
• What is the main principle of the area-velocity method for discharge measurement?

  Measuring cross-sectional area and velocity
• Criteria for selecting a gauging site in the area-velocity method:

  1️⃣ Well-defined cross section

  2️⃣ Easily accessible

  3️⃣ Straight, stable reach

  4️⃣ Free from backwater effects
• What instrument is used for quick and accurate depth measurements in streams with large depths?

  Echo-depth recorder
• Echo-depth recorders use high-frequency sound waves to measure stream depth.
• What increases the accuracy of discharge estimation in the area-velocity method?

  Number of subsections
• In the mid-sections method, the total discharge is calculated by dividing the area into N-1 segments.
• What is another name for the dilution method of streamflow measurement?

  Chemical method
• The dilution method depends on the continuity principle applied to a tracer that mixes completely with the flow.
• In the sudden injection method, what is the base value of tracer concentration in the streamflow?

  Co