Example

Problem 1: Velocity-Area Method (Mid-Section Method) A stream cross-section is divided into three vertical segments to measure discharge.
  • Segment 1: width = 2.0 m2.0 \text{ m}, depth = 1.0 m1.0 \text{ m}, mean velocity = 0.5 m/s0.5 \text{ m/s}.
  • Segment 2: width = 3.0 m3.0 \text{ m}, depth = 2.0 m2.0 \text{ m}, mean velocity = 1.0 m/s1.0 \text{ m/s}.
  • Segment 3: width = 2.0 m2.0 \text{ m}, depth = 0.5 m0.5 \text{ m}, mean velocity = 0.3 m/s0.3 \text{ m/s}. Calculate the total discharge (QQ) of the stream.

Solution: Mid-Section Method Calculation

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Example

Problem 2: Estimating Mean Velocity using the 2-Point Method A hydrologist is measuring flow in a deep river segment. The total depth of the segment is 4.0 m4.0 \text{ m}. Using a current meter, the velocity measured at 0.8 m0.8 \text{ m} below the surface is 1.2 m/s1.2 \text{ m/s}, and the velocity measured at 3.2 m3.2 \text{ m} below the surface is 0.6 m/s0.6 \text{ m/s}. Calculate the estimated mean velocity of the vertical profile.

Solution: 2-Point Velocity Calculation

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Example

Problem 3: Stage-Discharge Relationship (Rating Curve) A river gauging station has an established stage-discharge rating curve defined by the equation Q=15(G0.5)1.5Q = 15(G - 0.5)^{1.5}, where QQ is the discharge in m3/s\text{m}^3\text{/s} and GG is the gauge height (stage) in meters. The constant 0.50.5 represents the gauge height of zero flow (aa). If the current stage reading is 2.5 m2.5 \text{ m}, calculate the estimated discharge.

Solution: Rating Curve Application

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Example

Case Study 1: The Importance of Rating Curve Calibration A severe flash flood occurs on a river, resulting in extreme high flows that scour the riverbed and alter its cross-section. Discuss why the hydrologist must immediately perform new current-meter measurements after the flood waters recede, rather than relying on the existing rating curve.

Analysis: Rating Curve Dynamics

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Example

Case Study 2: Advancements in Discharge Measurement (ADCP vs. Current Meters) Historically, discharge was measured manually by wading into a stream with a mechanical current meter. Today, Acoustic Doppler Current Profilers (ADCPs) are widely used. Discuss the technological advantages of using an ADCP for streamflow measurement.

Analysis: ADCP Technology

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