measurement of stream discharge by wading
TRANSCRIPT
![Page 1: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/1.jpg)
Measurement of Stream Discharge by WadingWater Resources Investigations Report 00-4036
By K. M. Nolan and R. R. Shields
![Page 2: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/2.jpg)
Reference materials
![Page 3: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/3.jpg)
Agenda
•The velocity-area concept
•Making the measurement
•Measuring width
•Measuring depth
•Wading rod use
•Measuring velocity
•Site selection
![Page 4: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/4.jpg)
x Water Velocity
Cross section area
Discharge = (Area of water in cross section) x (Water velocity)
THE VELOCITY-AREA METHOD
![Page 5: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/5.jpg)
Discharge of each sub-section = Area x Average Water Velocity
Channel cross section is divided into
numerous sub sections
![Page 6: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/6.jpg)
Width
Depth
Area = Width x Depth
Area of each sub-section determined by directly
measuring width and depth
![Page 7: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/7.jpg)
Water velocity in each sub-section
is estimated using a current meter
to measure water velocity at
selected locations
![Page 8: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/8.jpg)
Total Discharge = ((Area1 x Velocity 1) + (Area2 x Velocity2) + ….. (Arean x Velocityn))
1 2 3
Stream discharge is sum of discharges in
all sub-sections
n
![Page 9: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/9.jpg)
Computing width and depth of individual
subsections
• Example of computing
sub-section width
• Assume the following
measurements applied
• Starting point - 0 feet
• Next point - 1 feet
• Next point - 3 feet
• Next point - 5 feet
0 1 3 5
Meter locations
![Page 10: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/10.jpg)
Recording Width
• Width at point 0 = (1 - 0)/2 = 0.5
• Width at point 1 - (3 - 0)/2 = 1.5
• Width at point 3 = (5 - 1)/2 = 2.0
0 1 3 5
1.5
2
Meter locations (ft.)
Widths
0.5
?
![Page 11: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/11.jpg)
Recording Width and Depth
0 1 3 5
1.5
2
Meter locations
Widths
0.5
?
Depth, in this
example, is
zero, therefore
no flow
Note: See table from Rantz
(1982) for help estimating
velocity when edge of water is
vertical.
![Page 12: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/12.jpg)
Measuring Cross-Section Area
Width
![Page 13: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/13.jpg)
Measuring Cross-Section Area
Depth
• Wading
rod is
marked
every
0.1 foot
![Page 14: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/14.jpg)
Wading Rod Use• Stand beside and downstream of rod
![Page 15: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/15.jpg)
10
8
6
4
2
0
2
6
5
4
3
7
8
0.6
Depth2.6 ft.
Total
Depth
0.8
Depth
0.2 depth
Setting
RodDepth
Scale
Rod set so
meter placed
at 0.6 (2.6 ft)
2.08 ft.
0.52 ft.
1.04 ft.
Wading
Rod Use
(cont.)
![Page 16: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/16.jpg)
Wading Rod Use (cont.) • Must estimate depth when velocity
causes “pile-up” on rod.
• Visually extend water surface to
rod.
![Page 17: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/17.jpg)
Velocity Determination
• USGS generally uses
Price current meters
• AA for large depths
• Pygmy for shallow
depthsStandard AA Meter
Pygmy Meter
See OSW memos 85.07
and 85.14
![Page 18: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/18.jpg)
Meter Depth
range
(ft.)
Recommended
velocity range
(ft/s)
Price AA > 1.5 0.10 - 12
Pygmy 0.3 – 1.5 0.5 - 12
Meter Use
![Page 19: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/19.jpg)
Headset and Stopwatch
• Velocity is determined
by placing meter in
stream and counting
number of revolutions
in a measured amount
of time
Stop Watch and Headset
![Page 20: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/20.jpg)
Measure velocity for at least 40
seconds
• Velocity should be measured for at least 40 seconds
• Evens out short-term velocity fluctuations
![Page 21: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/21.jpg)
Marking Meter• Meter revolutions can
sometimes be counted
manually by marking
one meter cup.
![Page 22: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/22.jpg)
Rating Table
• Velocity can
then be
determined
using a
current-meter
rating table
Partial listing of standard rating #2
![Page 23: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/23.jpg)
Rating Table Equations
• Equations for standard Rating Tables:
For AA meter
• V = 2.2048 R + 0.0178
For pygmy meter
• V = 0.9604 R + 0.0312
R = Revolutions per second
See:
•OSW Memo 99.05
![Page 24: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/24.jpg)
Velocity from Digitizer, Aquacalc,
and DMX• Current meter digitizers
Aquacalcs and DMX
units have equations for
rating table built in.
• These devices provide
direct computation of
velocity
![Page 25: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/25.jpg)
Average Velocity
• The goal is to represent the
average velocity in the
vertical
• Measured at 0.6 the
depth when depths are
shallow
• Measured at 0.2 and
0.8 the depth when
depths are large. These
two velocities are
averaged to represent
average velocity in the
vertical
Typical velocity profile
0
10
20
30
40
50
60
70
80
90
100
0 0.5 1 1.5
Velocity, in feet per second
Dis
tan
ce b
elo
w w
ate
r s
urfa
ce i
n
percen
tag
e o
f to
tal
dep
th
![Page 26: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/26.jpg)
10
8
6
4
2
0
2
6
5
4
3
7
8
0.6
Depth2.6 ft.
Total
Depth
0.8
Depth
0.2 depth
Setting
RodDepth
Scale
Rod set so
meter placed
at 0.6 (2.6 ft)
2.08 ft.
0.52 ft.
1.04 ft.
Wading
Rod Use.
![Page 27: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/27.jpg)
Velocity Measurement Methods
Guide to velocity-measurement methodsDepth, in ft. Meter Velocity Method
2.5 ft and above Type AA 0.2 and 0.8
1.5 – 2.5 Type AA 0.6
0.3 – 1.5 Pygmy 0.6
1.5 ft and above Pygmy 0.2 and 0.8
![Page 28: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/28.jpg)
Non Standard Conditions
•Use of 0.6 and 0.2/0.8 methods assume velocity profile is
logarithmic.
•Velocity should decrease closer to bottom due to friction
•If velocity at 0.8 depth is greater than velocity at 0.2 depth
or if velocity at 0.2 depth is twice the velocity at 0.8 depth
then the velocity profile is considered abnormal and the
three-point method must be used.
![Page 29: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/29.jpg)
0
10
20
30
40
50
60
70
80
90
100
0 0.5 1 1.5
Velocity, in feet per second
Dis
tan
ce b
elo
w w
ate
r s
urfa
ce i
n
percen
tag
e o
f to
tal
dep
th
Three-Point Method
• Three-point method
computed by
averaging velocity
measured at 0.2 and
0.8 the depth and
averaging that result
with velocity
measured at 0.6 the
depth.
![Page 30: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/30.jpg)
Site Selection
•Reach should be straight
and uniform for a long
enough distance to provide
uniform flow through the
measuring section
•Streambed should be stable
and free of large rocks,
weeds, and protruding
obstructions.Upstream view of excellent
measuring section, Little Blackfoot
River
![Page 31: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/31.jpg)
Assessing Measurement
• Assessing accuracy of measurement
•Semi-quantitative based upon:
1. Cross section uniformity
2. Velocity uniformity
3. Stream bed conditions
4. Etc.
See “Determination of Error in
Individual Discharge
Measurements” by Sauer and
Meyer announced in OSW
memo 93.14
Blackfoot measuring section
![Page 32: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/32.jpg)
Assessing Measurement (cont.)
Measurement
Rating
Percent off from true
discharge
Excellent Within 2
Good Within 5
Fair Within 8
Poor Greater than 8
![Page 33: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/33.jpg)
Selected References• Buchanan, T.J., and Somers, W.P., 1969, Discharge measurements at gaging
stations: USGS Techniques of Water-Resources Investigations, Book 3, Chapter
A8, 65 p. (In revision)
• International Organization for Standardization, 1983, Measurement of liquid
flow in open channels, Handbook 16, 518 p.
• Nolan, K.M. and others, Surface-water field techniques training class, USGS
WRIR 98-4252, (http://wwwrcamnl.wr.usgs.gov/sws/fieldmethods)
• Rantz, S.E., 1982, Measurement and Computation of Streamflow:Volumes I and
II, USGS Water Supply Paper 2175, 631 p.
• V.B.Sauer and R.W. Meyer, Determination of Error in Individual Discharge
Measurements”, USGS Open-file report 92-144
![Page 34: Measurement of Stream Discharge by Wading](https://reader031.vdocuments.site/reader031/viewer/2022020119/5868cb0e1a28abcd408c0901/html5/thumbnails/34.jpg)
Charlie Peterson
Spokane County
Conservation District
210 North Havana Street
Spokane, WA 99202
(509) 535-7274
http://www.sccd.org
For more information: