# Engineering Hydrology Questions and Answers – Streamflow – Stage Measurement – Set 2

This set of Engineering Hydrology Multiple Choice Questions & Answers (MCQs) focuses on “Streamflow – Stage Measurement – Set 2”.

1. What is the primary use of the stilling well unit in a float-gauge stage recorder?
a) Balancing the weight of the float
b) Dampen effects of surface waves on readings
c) To protect apparatus from harsh conditions
d) To house the recorder setup

Explanation: The use of a stilling well is to reduce the effects of water surface waves on the recordings while permitting the natural increase or decrease of the water level. Hence, it is provided in all float-gauge type stage recorders.

2. The pulley in a float type stage recorder is present in which component?
a) Counterweight
b) Float
c) Walkway
d) Recorder

Explanation: The pulley is present inside the recorder unit and has a float and a counterweight attached to both its ends, respectively. The pulley is a means of measuring the linear distance moved by the float in terms of angular measurements.

3. What is the sequence of displacements in a float-gauge recorder from the movement of the float to the recording of stage?
a) Linear-angular
b) Angular-linear
c) Linear-angular-linear
d) Angular-linear-angular

Explanation: When the water level rises or lowers, the float attached to the pulley also covers the same linear distance in the respective direction. This causes a rotation of the pulley (clockwise or anti-clockwise) which is converted to a linear output by linkages attached to pen to record the stage over a rotating drum.

4. Which of the following helps in protecting the float of a float type stage recorder from debris?
a) Flush tank
b) Intake pipes
c) Unit enclosure
d) Stilling well

Explanation: The intake pipes and flush tank are a part of the stilling well arrangement in a float-gauge recorder. The pipes bring the water from the river in and the flushing setup helps to remove the sediments and debris from the incoming water.

5. What is the output plot of a float-gauge recorder?
a) Stage vs. time
b) Flow vs. time
c) Stage vs. flow
d) Flow vs. depth

Explanation: The pen is run over a drum recorder driven by clockwork for a stipulated time like a day or a week. This enables us to obtain a continuous plot of the varying water levels of the river with time. This is known as a stage hydrograph.

6. Which of the following is not a use of stage hydrographs?
a) Determination of reservoir capacity
b) Design of hydraulic structures
c) Flood warning and flood protection works
d) Determination of stream discharge

Explanation: Stage data is an important parameter and has multiple uses in hydrologic studies. It is used to determine the river discharge to give information regarding floods and flood protection works to be proposed. Stage data can also be used to estimate the design peak stage for use in the design of hydraulic structures.

7. Which of the following is not an advantage of a bubble-gauge recorder over a float-gauge stage recorder?
a) Absence of expensive stilling well unit
b) Measurement of small changes in stage
c) Recorder assembly can be kept far from sensing point
d) Less chance of inlet getting blocked

Explanation: The bubble-gauge has some significant advantages over a float-gauge recorder. However, the ability of measurement of small changes in stage is not one of them as it can also be effectively done by a float type recorder. In fact, the advantage of a bubble gauge is that it can measure large changes in stage, upto 30 m.

8. What is the location of the gas outlet in a bubble-gauge setup?
a) Water surface
b) 0.6 times the depth below the water surface
c) River bottom
d) 0.2 times the depth below the water surface

Explanation: The outlet is placed at the bottom of the river and is used to bleed the compressed air at a small rate. The gas pressure is equal to the column of water above the outlet, and this is measured by the pressure gauge.

9. Steven’s type F water-depth recorder is an example of a float-gauge stage recorder.
a) True
b) False

Explanation: Stevens type F recorder consists of a pulley mechanism and is part of a float-gauge stage recorder system. Stevens manometer servo is an example of bubble-gauge recorder unit.

10. What is the use of a servo mechanism in a bubble-gauge stage recorder?
b) Pressure measurement

Explanation: When the water surface level changes, a change in pressure (due to water column) is noted in the pressure gauge from the initial value. A servo mechanism in a gas adjustment unit is used to change the rate of gas bleeding from the outlet to the initial rate.

Sanfoundry Global Education & Learning Series – Engineering Hydrology.

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