Streamflow Measurement Flashcards
Objective Questions
The science and practice of water flow measurement is known as
hydrometry
The following is not a direct stream flow determination technique:
Slope-area method
A stilling well is required when the stage measurement is made by employing a
float gauge recorder
In the moving-boat method of stream-flow measurement, the essential measurements
are
the velocity and direction of the current meter, the depths and the time interval
between depth readings
Which of the following instruments is not connected with stream flow measurement?
Hygrometer
The surface velocity at any vertical section of a stream is
larger than the mean velocity in that vertical section
If a gauging section is having shifting control due to backwater effects then
a secondary gauge downstream of the section is needed
The stage discharge relation in a river during the passage of a flood wave is measured.
If QR = discharge at a stage when the water surface was rising and QF = discharge at
the same stage when the water surface was falling then
QR > QF
The dilution method of stream gauging is ideally suited for measuring discharges in
steady flow in a small turbulent stream
The slope-area method is extensively used in
estimation of flood discharge based on high-water marks
For a given stream, the rating curve applicable to a section is available. To determine
the discharge in this stream, the following-data are needed
Stage at the section
During a flood in a wide rectangular channel, it is found that at a section the depth of
flow increases by 50% and at this depth the water-surface slope is half its original value
in a given interval of time. This marks an approximate change in the discharge of
+39%
In a river, the discharge was 173 m3/s, the water surface slope was 1 in 6000 and the
stage at the station X was 10.00 m. If during a flood, the stage at station X was 10.00
and the water surface slope was 1/2000, the flood discharge was approximately
300 m3/s
During a flood, the water surface at a section was found to decrease at a rate of 10 cm/h.
The slope of the river is 1/3600. Assuming the velocity of the flood wave as 2 m/s, the
actual discharge in the stream can be estimated as
2.5% smaller than the normal discharge
Representing the runoff
phase of the hydrologic cycle is the
most important basic data for hydrologic
studies.
Streamflow
A (blank) can be defined as a flow
channel into which the surface runoff
from a specified basin drains.
Stream
Streamflow measurement techniques
can be broadly classified into two
categories as?
Direct determination, Indirect determination
The simplest of stage measurements are made by noting the elevation of the
water surface in contact with a fixed graduated staff.
Staff Gauge
Sometimes, it may not be possible to read the
entire range of water-surface elevations of a stream by a single gauge and in such cases
the gauge is built in sections at different locations. Such gauges are called?
Sectional Gauges
It is a gauge used to measure the water-surface elevation from above the surface such
as from a bridge or similar structure.
Wire Gauge
The most common type of automatic
stage recorder in use.
float-operated stage recorder
To protect the float from debris and to reduce the water surface wave effects on
the recording, (blank) are provided in all float-type stage recorder installations
stilling wells
In this gauge, compressed air or gas is made to bleed out at a very small rate through
an outlet placed at the bottom of the river.
Bubble Gauge
The stage data is often presented in the
form of a plot of stage against chronological
time known as?
stage hydrograph
A mechanical device consisting essentially of a rotating element is probably the most commonly used instrument for
accurate determination of the stream-velocity field.
current meter
Approximate stream velocities
can be determined by?
Floats
The most commonly used instrument in hydrometry to measure the velocity at a
point in the flow cross-section is the?
current meter
Two main types of current meters?
Vertical - axis meters, Horizontal - axis meters
The relation between the stream velocity and revolutions per second of the meter is called?
calibration equation
A (blank) is a long channel containing still water with arrangements for moving
a carriage longitudinally over its surface at constant speed.
towing tank
