Question

What is the process of measuring water discharge in rivers and streams?

• A. Rain gauging
• B. Infiltration measurement
• C. Stream gauging
• D. Transpiration monitoring

Hint:

• Stream gauging (or streamflow measurement) is the process of quantifying the discharge (flow rate) of water in rivers and streams.
• Common methods include the velocity-area method, dilution gauging, and use of weirs/flumes or rating curves.
• Rain gauging measures rainfall.
• Infiltration measurement measures water entry into soil.
• Transpiration monitoring measures water release from plants.

Answer 1

The Correct Option is C

The process of measuring the volume of water flowing past a specific point in a river or stream per unit of time (i.e., discharge or flow rate) is known as stream gauging or streamflow measurement. Stream gauging involves various techniques:

• Direct methods:
  • Velocity-area method: Measuring the average flow velocity and the cross-sectional area of flow. Discharge (Q) = Area (A) $\times$ Velocity (V). Velocity can be measured using current meters, ADCPs (Acoustic Doppler Current Profilers).
  • Volumetric gauging: Directly measuring the volume of water collected over a period (for very small streams).
  • Dilution gauging: Introducing a tracer and measuring its dilution downstream.
• Indirect methods:
  • Using hydraulic structures like weirs or flumes where discharge is related to water level through a known formula.
  • Using stage-discharge relationships (rating curves) where continuous measurement of water level (stage) is used to estimate discharge.

Option (c) Stream gauging is the correct term for this process. Other options: Option (a) Rain gauging: The process of measuring the amount of rainfall using rain gauges. Option (b) Infiltration measurement: The process of measuring the rate at which water enters the soil, using instruments like infiltrometers. Option (d) Transpiration monitoring: The process of measuring the amount of water vapor released from plant leaves into the atmosphere, often done using lysimeters or sap flow sensors. \[ \boxed{\text{Stream gauging}} \]