how class works

Measurement of Stream Discharge by WadingWater Resources Investigations Report 00-4036

By K. M. Nolan and R. R. Shields

AgendaWater Resources Investigations Report 00-4036 Test

How class works

• Instructions for viewing and navigating through this training class can be found in the “Intro.html” file, which is on the CD-ROM containing this presentation.


Class Credit

• Listed as Training Class SW1271 with the National Training Center of U.S. Geological Survey

• Supervisor may ask to see a copy of the completed test

http://1stop.usgs.gov/ntc_homepage/


Links to reference materials

http://wwwrcamnl.wr.usgs.gov/sws/fieldmethods

USGS memos

Linked Text




Agenda• How this class works• The velocity-area concept• Making the measurement

• Measuring width • Measuring depth• Wading rod use• Measuring velocity• Site selection

• Safety• Measurement notes• Blackfoot River as an example

• Starting the measurement• The front sheet• Inside the note sheet• Job Hazard Analysis

• Horizontal angle correction• Computing subsection widt

h and depth• Recording velocity• Recording discharge

• Finalizing measurement• Mean Gage Height• Accuracy• The control• Point of zero flow• Plotting on rating

• Test• References• Acknowledgements


x Water Velocity

Cross section area

Discharge = (Area of water in cross section) x (Water velocity)

THE VELOCITY-AREA METHOD


Discharge of each sub-section = Area x Average Water Velocity

Channel cross section is divided into numerous sub sections


Width

Depth

Area = Width x Depth

Area of each sub-section determined by directly measuring width and depth


Water velocity in each sub-sectionis estimated using a current meterto measure water velocity atselected locations


Total Discharge = ((Area1 x Velocity 1) + (Area2 x Velocity2) + ….. (Arean x Velocityn))

1 2 3

Stream discharge is sum of discharges inall sub-sections

n


Making the Measurement• Verticals should be spaced so

no subsection has more than 10% of the total discharge

• Ideal measurement has no more than 5% of total discharge in any subsection

• Should have between 20 and 30 subsections

• Spacing between verticals should be closer in those parts of cross section with greater depths and velocities.


Measuring Cross-Section AreaWidth


Measuring Cross-Section AreaWidth (cont.)

•Taglines usually have marks

• One mark every 2 ft

• Some taglines have:

• Two marks every 10 ft

• Three marks every 100 ft.

• Distances between marks are estimated or measured


Measuring Cross-Section AreaDepth

•Wading rod is marked every 0.1 foot


Wading Rod UseTop Setting Mechanism


10 8 6 4 2 0

2

6

5

4

3

7

8

0.6 Depth

2.6 ft.TotalDepth

0.8Depth

0.2 depth

SettingRodDepth

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.)


Wading Rod Use (cont.) • Must estimate depth when velocity

causes “pile-up” on rod.

• Visually extend water surface to rod.


Wading Rod Use• Stand beside and downstream of rod


Velocity Determination

• USGS generally uses Price current meters

• AA for large depths

• Pygmy for shallow depths

Standard AA Meter

Pygmy Meter

See OSW memos 85.07 and 85.14


Meter Depthrange(ft.)

Recommendedvelocity range

(ft/s)Price AA > 1.5 0.10 - 12

Pygmy 0.3 – 1.5 0.5 - 12

Meter Use


Spin Tests• A spin test should be performed on

all meters:

• Before each field trip

• When performance is suspect.

• Before and after repairs

• A log of all spin tests must be maintained

• See OSW memo 89.07 for policy on spin tests


Meter Performance

• Meter performance should also be checked before and after each measurement

• Spin meter and note if meter spins freely and comes to gradual stop


Meter Care

• Meter care and maintenance is discussed in OSW memorandum 99.06


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


Digitizer, Aquacalc and DMX 1

• Newer units are now available that compute velocity and/or discharge

Digitizer

Aquacalc

DMX

1Use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government


Marking Meter• Meter revolutions can

sometimes be counted manually by marking one meter cup.


Rating Table

• Velocity can then determined using a current-meter rating table

Partial listing of standard rating #2


Rating Table Equations• Equations for standard Rating Tables:

For AA meter• V = 2.2048 R + 0.0178For pygmy meter

• V = 0.9604 R + 0.0312

R = Revolutions per second

See:• OSW Memo 99.05• Standard rating table #2 for AA meter • Standard rating table #2 for Pygmy meter


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


Measure velocity for at least 40 seconds

• Velocity should be measured for at least 40 seconds

• Evens out short-term velocity fluctuations


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

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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


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 (see next slide).


0

10

20

30

40

50

60

70

80

90

100

0 0.5 1 1.5

Velocity, in feet per second

Dis

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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.


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


ControlMeasurement Section

W

5W 2W

Site Selection (cont.)

• Straight and uniform for a distance long enough to support uniform flow

Rif

fle

Flow


Safety - First

Standard PFDThrow Bag

Inflatable PFD

“Safety First, Every Job, Every Time”(Department of Interior Policy)


Safety – On Line

http://wwwhif.er.usgs.gov/uo/safety.html

http://wwwhif.er.usgs.gov/uo/safety.html


Safety – Memo 99.32

Water Resources Division Memorandum 99.32


Safety – miscellaneous memosMemo Number Description

Personal Floatation DevicesOP 88.01 Use of Life Jackets and Personal Flotation Devices

Confined SpaceWRD 94.30 Plan for Insuring Safe Work in Gaging Station Stilling WellsWRD 97.32 Updated Interim Safety Guidelines for Safe Entry and Work in

WRD Gaging StationsWRD 95.02 Plan for Insuring Safe Work in Gaging Station Stilling Wells –

A Follow-up to WRD Memorandum 94.30WRD 98.17 WRD Respiratory Protection Program Requirement

Safety at USGS Gaging StationsWRD 69.92 Field Installation Safety RequirementsOP 94.01 Hantavirus Infection PreventionWRD 97.32 WRD Gaging Station Stilling Wells

USGS Gaging Stations with Mercury ManometersWRD 91.58 WRD Policy on Phase-Out of ManometersWRD 92.32 WRD Policy on Phase–Out of ManometersHIF 92.14 Instructions on Disposing of Mercury ManometersOP 96.03 Supplies Information on Disposal of Mercury Manometers

Use of Government VehiclesWRD 98.25 Motor Vehicle Driver Training

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Safety – ResponsibilitiesWRD Memo 99.32 - “Both supervisors and employees will be held accountable if safety policies are not followed.”

Winter measurementSnake River near Moran, WY


Safety - PFDs

See WRD Memo 99.32• Personal Flotation Devices (PFDs) must be worn

unless the job hazard analysis states otherwise.

Standard PFD Suspender-type PFD


• Protection against hypothermia is required when conditions warrant.

• WRD Safety Home Page contains information on protection against hypothermia

• Use of cold water protective Personal Flotation Devices increases protection against hypothermia

Float Coat

Safety- Hypothermia

http://wwwhif.er.usgs.gov/uo/safety/hypothermia.htm

http://wwwhif.er.usgs.gov/uo/safety/hypothermia.htm


Safety - Rescue• Look downstream and think

rescue

Downstream view of measurement section, Clark Fork, near Gold Cr., MT


Safety - Rescue • Throw bags contain a line that can be thrown to colleagues who need help.

• See Mississippi report on use of multi-person field trips


Wading Safely

• When wading, proceed carefully

• Use wading rod to probe bottom ahead of you


Wading Safely (cont.)

• Wade carefully and think about hazards downstream

•How would you execute a self-rescue at this site?•Have a plan before you begin


Safety – Conditions Around You

Be aware of potentially dangerous conditions upstream and downstream• Ice• Debris• Dam Releases• Boats

Snake River near Moran, WY


Safety – Measuring Width

Laser distance meter

• Use laser distance meter, rather than a tag line, to measure channel width and distances when boat traffic is possible


Safety - Traction• Use of felt soles or metal cleats on the

bottom of your waders can significantly improve traction.

• Be careful, felt bottoms can become slick if algae is present.


Safety - Waders

• Belts can prevent waders from rapidly filling with water, if you fall below the water level.

Belt


Safety--In-Pool Training


Measurement Notes9-275-F UNITED STATES Meas. No…………(Rev. 10-81) DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY Comp. by………….

WATER RESOURCES DIVISION

Sta. No………………….. DISCHARGE MEASUREMENT NOTES Checked by………………………………………………………………………………………………………………………Date…………….., 19…………………… Party……………………………………………………………Width……………. Area………………… Vel………… G.H………………… Disch……………………Method……….. No. secs…………….. G.H. change………… in ………..hrs. Susp…………….Method coef……….. Hor. Angle coef…………… Susp. Coef…………………. Meter No…………Type of meter……………. Date rated …………………………. Tag checked …………………………..Meter …………. Ft. above bottom of wt. Spin before meas…………….. after …………………………Meas. Plots……….. % diff. From ……….. rating. Levels obtained …………………………………..

Gage Readings Water Quality MeasurementsTime Inside ADR Graphic Outside No……….. Yes………. Time ……….……………………………………………………….……. Samples Collected……………………………………………………..……. No………. Yes……….. Time………………………………………………………………..…… Method Used………………………………………………………….. EDI……… EWI………. Other………..……………………………………………………. …… SEDIMENT SAMPLE………………………………………………………….. No………… Yes……… Time……....………………………………………………………….. Method Used EDI……….. EWI……… Other……….Weighted M.G.H. ………………………………… BIOLOGICAL SAMPLESG. H. Correction ………………………………….. Yes………………….. Time……………….Correct M.G.H. …………………………………. No…………….……. Type………………

Check bar chain found……………………………….. changed to …………………… at ……………..


Measurement Notes -Example

• The process of filling out measurement note sheets will be examined by following a measurement made on the North Fork Blackfoot River on September 13, 1999

Upstream view, North Fork, Blackfoot River

Gage House


N. Fk. Blackfoot River

Downstream View Upstream View


Gage House


Starting the MeasurementN. Fork Blackfoot River

• Discussion of measurement

• Overview of gage site


Selecting Measuring Section


Measuring Section

Downstream view showing control riffle


Stringing Tagline


Meter and Rod Setup


Meter and Rod Setup (cont.)


Determining Subsection Spacing

• Remember, try to have no more than 5% of flow in any one subsection


Assessing Subsection Spacing

• Can keep track of sectioning by using rating to estimate what discharge will be.


Assessing Subsection Spacing (cont.)

• Try to monitor flow in each section as you proceed.

• It is most important to monitor flow in the deepest/fastest subsections to judge compliance to the 5% rule.


Starting the Measurement – The Second Subsection


Job Hazard Analysis

Job Hazard Analysis for North Fork Blackfoot River Site


Front Sheet

Summarizes: 1. Measurement

results2. Gage operation3. Channel conditions4. Evidence of high-

water5. Water Samples

taken during visit

9-275-F UNITED STATES Meas. No…………(Rev. 10-81) DEPARTMENT OF THE INTERIOR



Sta. No ………….……. DISCHARGE MEASUREMENT NOTES Checked by…………………………………..…………………………………………………………………………….……Date……….. ……………… Party……………..………………………………….. ……..………………Width……..…. Area……..……… Vel……….G.H……………………….…… Disch…….……………Method………….. No. secs…..…….... G.H. change…..…. in …...…..hrs. Susp. .………..……Method coef……….. Hor. Angle coef…………… Susp. Coef…………………. Meter No………..Type of meter……………. Date rated …………………………. Tag checked …………………………..Meter …………. Ft. above bottom of wt. Spin before meas…………….. after …………………………Meas. Plots……….. % diff. From ……….. rating. Levels obtained …………………………………..

Gage Readings Water Quality MeasurementsTime Inside ADR Graphic Outside No……….. Yes………. Time ……….……………………………………………………….……. Samples Collected……………………………………………………..……. No………. Yes……….. Time………………………………………………………………..…… Method Used………………………………………………………….. EDI……… EWI………. Other………..……………………………………………………. …… SEDIMENT SAMPLE………………………………………………………….. No………… Yes……… Time……....………………………………………………………….. Method Used EDI……….. EWI……… Other……….Weighted M.G.H. ………………………………… BIOLOGICAL SAMPLESG. H. Correction ………………………………….. Yes………………….. Time……………….Correct M.G.H. …………………………………. No…………….……. Type………………

Check bar chain found……………………………….. changed to …………………… at ……………..Wading, cable, ice, boat, upstr., downstrn., side bridge……………. Feet, mile, above, below gage.Measurement rated exellent (2%), good (5%), fair (8%), poor (over 8%); based on the following cond.Flow……………………………………………………………………………………………………….Cross section………………………………………………………………………………………………Control…………………………………………………………………………………………………….Gage operating………………………………………… Weather………………………………………..Intake/Orifice cleaned…………… Air……………..oC@……….. Water……………oC@…………….Record removed……………… Extreme Indicator: Max………………… Min…………………………Manometer N2 Presure Tank……………… Feed………… Bbl rate………………………….. per min.CSG checked………………………………….. Stick reading……………………………………………Observer……………………………………………………………………………………………………HWM……………………………………………………………………. outside, in wellRemarks…………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………………………………………………………………G.H. of zero flow………………… ft. Sheet No…………………… of ………………….. sheets


9-275-F UNITED STATES Meas. No…37……(Rev. 10-81) DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY Comp. by…RRS…. WATER RESOURCES DIVISION

Sta. No…12338300 DISHARGE MEASUREMENT NOTES Checked by.Q ck……N.F. Blackfoot R. ab. Dry Gulch nr. Ovando, MT…………........................................………………Date…09/13….., 1999…………………… Party…Shields (m/n), M. Nolan, K. Thompson…………..…Width…110……. Area…139…………… Vel…1.47… G.H…2.79………… Disch…205……...………Method…0.6….. No. secs…29 ……….. G.H. change…0…… in …1…..hrs. Susp…Rod…...….Method coef…---….. Hor. Angle coef…---……… Susp. Coef……---…………... Meter No…272409…Type of meter…AA-Mag. Date rated …July 1999…………. Tag checked ………N/A………....………..Meter …-----…. Ft. above bottom of wt. Spin before meas…4' 30"…….. after ……O.K.…….…………Meas. Plots…-16….. % diff. From …Rt. #1….. rating. Levels obtained ……No………………………..

Summary Information - Blackfoot Measurement


Gage equipment 1

Gage Readings Water Quality MeasurementsTime Inside DCP Graphic Outside No…x….. Yes………. Time ……….…1130……........……2.79……2.79……2.79......2.78 +/-.02 Samples Collected……………………………………………………..…..…. No…x…... Yes……….. Time…………1200…………………………2.79………………..….….. Method Used1230…………………………2.79……………………..... EDI……… EWI………. Other………..……………………………………………………. …… .. SEDIMENT SAMPLE1245………………2.79………………2.79….2.78 +/-.02 No…x…… Yes……… Time……....………………………………………………………….. .. Method Used EDI……….. EWI……… Other……….Weighted M.G.H. … 2.79………………...........…………... BIOLOGICAL SAMPLESG. H. Correction ……………………….......………….. ... Yes………………….. Time…………….Correct M.G.H. ………………………........………….... No………x……..…. Type……………

Check bar chain found…………N/A………………….. changed to …………………… at ……………..Wading, cable, ice, boat, upstr., downstrn., side bridge…100……. Feet, mile, above, below gage.Measurement rated excellent (2%), good (5%), fair (8%), poor (over 8%); based on the following cond.Flow……Steady/Uniform……………………………………………………………………………….Cross section………Cobble/Gravel……………………………………………………………………Control……Riffle - 250 ft. below gage/ No algae or debris………………….……………………….Gage operating………Yes……………………………… Weather…Clear……………………………..Intake/Orifice cleaned…O.K.…… Air…20………..oC@…1130.. Water…10.8……oC@…1300…….Record removed……………… Extreme Indicator: Max………………… Min…………………………Manometer N2 Presure Tank…N/A……… Feed………… Bbl rate………………………….. per min.CSG checked……N/A……………………….. Stick reading……………………………………………Observer……………………………………………………………………………………………………HWM……………………………………………………………………. outside, in wellRemarks…Documented for training……Used Current Meter Digitizer with standard rating #2………………………………………………………………………………………………………………………………………………………………………………………………………………………………………G.H. of zero flow………………… ft. Sheet No………1…………… of ……2………….. sheets

1Use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government

Summary Information - Blackfoot Measurement (cont.)


Inside the note sheet

.0 .10 .20 .30 .40 .50 .60 .70 .75

River at--Anglecoef-ficient

Dist.Frominitialpoint

Width Depth Observationdepth

Revolutions

Time inseconds

VELOCITYAt MeanPoint in vertical

Ad-justedforhor.Angleor

Area Discharge .

.0 .10 .20 .30 .40 .50 .60 .70 .75

.80

0.85

.90

.92

.94

.96

.97

.98

.99

1.00

.99

.98

.97

.96

.94

.92

.90

.85

.80


Recording Width and Depth

Anglecoef-ficient



Revolutions

Time inseconds



Area Discharge .

• Distance from initial point - usually measured from left bank

• Depth - usually measured directly using a wading rod.


Recording Angle Correction

Anglecoef-ficient



Revolutions

Time inseconds



Area Discharge .

• Angle coefficient- correction applied if flow is not perpendicular to the cross section

• Needed because we must determine flow normal to the stream cross section.

• Angle of the current can be assessed by observing floating particles in the water

• Correction can be determined using measurement note sheet as guide (see next slide)


Determining a horizontal angle correction

Point of origin Read angle correction here

Tagline or tapeNoteSheet


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



0 1 3 5

Meter locations


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

?


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.


Recording Width and Depth (cont.)

• Data from the North Fork Blackfoot RiverAngle

coef-ficient


Width Depth Observation depth

REW 1135106 1.0 0 ----104 3.0 0.55 0.6100 5.0 .62

94 5.0 .62

90 5.0 .72

84 5.0 .90

80 4.0 1.20

76 4.0 1.40

72 3.5 1.45

69 3.5 1.60


Recording Velocity

Anglecoef-ficient



Revolutions

Time inseconds



Area Discharge .

• Velocity measured for at least 40 sec.

• Rating table for meter is used to determine velocity “at point”

• Any needed horizontal angle correction is applied to velocity


Recording Velocity (cont.)Anglecoef-ficient



Revolutions

Time inseconds



Area Discharge .

• Velocity measured at a

single point is entered in the “At Point” column

• If velocity is measured at more than one point in the vertical the mean must be computed.


Checking Meter Condition

• Condition of meter should be checked periodically to make sure debris is not affecting performance


Velocity from Rating Table

See OSW memo 99.05 for the most recent ratings for AA and pygmy meters.

Partial listing of standard rating #2


Recording Discharge• Data from North Fork Measurement

Angle coef-ficient

Dist. From initial point

Width

Depth

Observation depth

Revolutions

Time in seconds

VELOCITY At Mean Point in vertical

Adjusted for hor. Angle

Area

Discharge .

REW 1135 106 1.0 0 ---- ---- ----- --- ---- --- 0 0 104 3.0 0.55 0.6 19 41 1.04 1.65 1.7 100 5.0 .62 22 41.3 1.19 3.1 3.7 94 5.0 .62 19 40 1.07 3.1 3.3 90 5.0 .72 18 42.3 0.96 3.6 3.4 84 5.0 .90 26 40.7 1.43 4.5 6.4 80 4.0 1.20 29 40.7 1.59 4.8 7.6 76 4.0 1.40 32 40 1.78 5.6 10.0 72 3.5 1.45 34 40.9 1.85 5.08 9.4 69 3.5 1.60 30 40.8 1.64 5.6 9.2 65 3.5 1.56 33 40.3 1.82 5.46 10.0 62 3.5 1.45 34 40.6 1.86 5.08 9.5 58 3.5 1.40 32 40.4 1.76 4.90 8.6 55 3.5 1.55 33 40.6 1.81 5.43 9.8 51 3.5 1.42 32 41 1.74 4.97 8.6 48 3.5 1.50 34 40.9 1.85 5.25 9.7 44 3.5 1.40 36 40 2.00 4.9 9.8 1215 41 3.5 1.40 30 40 1.67 4.9 8.2 37 3.5 1.45 32 40.8 1.75 5.08 8.9


1215 41 3.5 1.40 30 40 1.67 4.9 8.2 37 3.5 1.45 32 40.8 1.75 5.08 8.9 34 3.5 1.45 32 41 1.74 5.08 8.8 30 3.5 1.50 20 40.3 1.55 5.25 8.1 27 3.5 1.58 28 41.1 1.52 5.53 8.4 23 3.5 1.80 28 40.1 1.56 6.3 9.8 20 4.0 1.80 17 41 0.93 7.2 6.7 15 5.0 1.80 21 40.5 1.16 9.0 10.4 10 5.0 1.60 21 40.9 1.15 8.0 9.2 5 5.0 1.10 12 42 0.65 5.5 3.6 1226 0 4.5 1.0 0.6 5 45.2 0.26 4.5 1.8 LEW -4 2.0 0 ----- --- ------ --- ---- ---- 0 0 110 110 139.4 204.6 110 110 139 205

Finalizing Measurement

• Include finish time

Finish time

Total widthTotal of all widths

Total areaTotal discharge

• Sum width, area and discharge

Intermediatetime


Finalizing Measurement (cont.)

• Record left edge of water, finish time, etc.

• A check of the discharge computation later revealed a discharge of 205 cubic feet per second

• Illustrates value of checking measurements



• Fill in Width, Area, Velocity, Gage height, and Discharge on Front Sheet

• Average velocity is (Discharge / Area)9-275-F UNITED STATES Meas. No…………(Rev. 10-81) DEPARTMENT OF THE INTERIOR



Sta. No ………….……. DISCHARGE MEASUREMENT NOTES Checked by…………………………………..…………………………………………………………………………….……Date……….. ……………… Party……………..………………………………….. ……..………………Width……..…. Area……..……… Vel……….G.H……………………….…… Disch…….……………Method………….. No. secs…..…….... G.H. change…..…. in …...…..hrs. Susp. .………..……Method coef……….. Hor. Angle coef…………… Susp. Coef…………………. Meter No………..Type of meter……………. Date rated …………………………. Tag checked …………………………..Meter …………. Ft. above bottom of wt. Spin before meas…………….. after …………………………Meas. Plots……….. % diff. From ……….. rating. Levels obtained …………………………………..



• Fill in Width, Area, Velocity, Gage height, and Discharge o Front Sheet

• Average velocity is (Discharge / Area)9-275-F UNITED STATES Meas. No…37……(Rev. 10-81) DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY Comp. by…RRS…. WATER RESOURCES DIVISION

Sta. No…12338300 DISHARGE MEASUREMENT NOTES Checked by.Q ck……N.F. Blackfoot R. ab. Dry Gulch nr. Ovando, MT…………........................................………………Date…09/13….., 1999…………………… Party…Shields (m/n), M. Nolan, K. Thompson…………..…Width…110……. Area…139…………… Vel…1.47… G.H…2.79………… Disch…205……...………Method…0.6….. No. secs…29 ……….. G.H. change…0…… in …1…..hrs. Susp…Rod…...….Method coef…---….. Hor. Angle coef…---……… Susp. Coef……---…………... Meter No…272409…Type of meter…AA-Mag. Date rated …July 1999…………. Tag checked ………N/A………....………..Meter …-----…. Ft. above bottom of wt. Spin before meas…4' 30"…….. after ……O.K.…….…………Meas. Plots…-16….. % diff. From …Rt. #1….. rating. Levels obtained ……No………………………..


Finalizing Measurement (cont.)• Read gage

• Record times and gage heights recorded during measurement on front sheet.

Gage Readings Water Quality Measurements Time Inside DCP Graphic Outside No…x….. Yes………. Time ……….… 1130……........……2.79……2.79……2.79......2.78 +/-.02 Samples Collected 1135 ...(s) …….... (2.79) …………………………..…..…. No…x…... Yes……….. Time………… 1200………………………….........………………..….….. Method Used 1226....(e)..………(2.79) .……………………………..... EDI……… EWI………. Other……….. 1230…………………………2.79………………. …… .. SEDIMENT SAMPLE 1245………………2.79………………2.79….2.78 +/-.02 No…x…… Yes……… Time…….... ………………………………………………………….. .. Method Used EDI……….. EWI……… Other………. Weighted M.G.H. … 2.79………………...........…………... BIOLOGICAL SAMPLES G. H. Correction ……………………….......………….. ... Yes………………….. Time……………. Correct M.G.H. ………………………........………….... No………x……..…. Type……………


Determining Mean Gage Height

• Compute mean gage height for measurement, if needed

• Mean gage height should be computed if change in stage is greater than 0.15 feet or if change in stage has not been uniform during measurement

• Weighting can be done using either partial discharge or time as the weighting factor

• See Discharge Measurements, Part 2 in training class SW4230 for a description of how weighting should be done.

http://wwwrcamnl.wr.usgs.gov/sws/fieldmethods/QMeas.tmp/index2.htm


Measurements During Rapidly Changing Stage

• Weighted mean gage height is not truly applicable when stage is changing rapidly

• You can reduce measurement time using the following procedures in the order listed:1. Use only the 0.6-depth method2. Reduce velocity-observation time to about 20-30 seconds3. Reduce the number of subsections to 15 – 18

• Using any of the shortcuts listed above will reduce measurement accuracy• See further discussion in SW4230

http://wwwrcamnl.wr.usgs.gov/sws/fieldmethods/QMeas.tmp/index2.htm



Check bar chain found……………………………….. changed to …………………… at ……………..Wading, cable, ice, boat, upstr., downstrn., side bridge……………. Feet, mile, above, below gage.Measurement rated exellent (2%), good (5%), fair (8%), poor (over 8%); based on the following cond.Flow……………………………………………………………………………………………………….Cross section………………………………………………………………………………………………Control…………………………………………………………………………………………………….Gage operating………………………………………… Weather………………………………………..Intake/Orifice cleaned…………… Air……………..oC@……….. Water……………oC@…………….Record removed……………… Extreme Indicator: Max………………… Min…………………………Manometer N2 Presure Tank……………… Feed………… Bbl rate………………………….. per min.

Downstream view through Blackfoot measuring reach


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


Assessing Measurement (cont.)

MeasurementRating

Percent off from truedischarge

Excellent Within 2

Good Within 5

Fair Within 8

Poor Greater than 8


Finalizing Measurement -- The Control

• Very important – Observations of control forms basis for developing shifts to ratings

• The control that is in effect during the measurement must be identified

ChannelControl

RiffleSection Control

ChannelControl

Water Surface

Stream Bottom


Finalizing Measurement -- The Control (cont.)

Section Control Section Control drowning out-- Channel becoming control


Check bar chain found…………N/A………………….. changed to …………………… at ……………..Wading, cable, ice, boat, upstr., downstrn., side bridge…100……. Feet, mile, above, below gage.Measurement rated excellent (2%), good (5%), fair (8%), poor (over 8%); based on the following cond.Flow……Steady/Uniform……………………………………………………………………………….Cross section………Cobble/Gravel……………………………………………………………………Control……Riffle - 250 ft. below gage/ No algae or debris………………….……………………….

Finalizing Measurement – Describing channel conditions


Finalizing measurement - Point of Zero Flow

• Point of zero flow (also called Gage Height of zero flow)• Useful in developing stage-discharge relation (rating)

• First approximation for scale offset• Can be used as another point on the rating

• Represented by the lowest (deepest) point on section control

Record removed……………… Extreme Indicator: Max………………… Min…………………………Manometer N2 Presure Tank……………… Feed………… Bbl rate………………………….. per min.CSG checked………………………………….. Stick reading……………………………………………Observer……………………………………………………………………………………………………HWM……………………………………………………………………. outside, in wellRemarks…………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………………………………………………………………G.H. of zero flow………………… ft. Sheet No…………………… of ………………….. sheets


Point of Zero Flow (cont.)

Gage Pool

Include Velocity Head

Deepest Point on Control

Control Section Perpendicular to Flow

Control Section

Gage Pool

Flow



North Fork Blackfoot River



Another example


High Water Marks

• Look for high-water marks

• Important aid in working streamflow record

• Allow you to verify peak stages recorded between visits to site

Record removed……………… Extreme Indicator: Max………………… Min…………………………Manometer N2 Presure Tank……………… Feed………… Bbl rate………………………….. per min.CSG checked………………………………….. Stick reading……………………………………………Observer……………………………………………………………………………………………………HWM……………………………………………………………………. outside, in wellRemarks…………………………………………………………………………………………………….………………………………………………………………………………………………………………………………………………………………………………………………………………………………G.H. of zero flow………………… ft. Sheet No…………………… of ………………….. sheets

High-water marks on North Fork staff gage


Measurement and the Stage-Discharge Relation

• Compute how far measurement plots from rating and plot on rating

Sta. No…12338300 DISHARGE MEASUREMENT NOTES Checked by.Q ck……N.F. Blackfoot R. ab. Dry Gulch nr. Ovando, MT…………........................................………………Date…09/13….., 1999…………………… Party…Shields (m/n), M. Nolan, K. Thompson…………..…Width…110……. Area…139…………… Vel…1.47… G.H…2.79………… Disch…205……...………Method…0.6….. No. secs…29 ……….. G.H. change…0…… in …1…..hrs. Susp…Rod…...….Method coef…---….. Hor. Angle coef…---……… Susp. Coef……---…………... Meter No…272409…Type of meter…AA-Mag. Date rated …July 1999…………. Tag checked ………N/A………....………..Meter …-----…. Ft. above bottom of wt. Spin before meas…4"30"…….. after ……O.K.…….…………Meas. Plots…-16….. % diff. From …Rt. #1….. rating. Levels obtained ……No………………………..


Test • Click on image on the left to start Excel file containing the test.

• You will have to allow Excel the use of macros for the test to function properly

• You should open the Excel file as “read only”.

• You can install the Excel Viewer, if you do not have Excel on your computer

• Clicking here will start installation


Wading Discharge Measurements Using the Mid-Section Method

ByK. Michael Nolan and Ronald R. Shields

Listed as Training Class SW1271 with National Training Center of U.S. Geological Survey

QuitView selected referencesAcknowledgements


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

Quit



AcknowledgementsThe authors would like to thank Glen Hess, Vern Sauer, and Lucky Sultz for their review of preliminary versions of this report. We appreciated the help of Ken Thompson during field work at the North Fork Blackfoot River. Funding for production and distribution of this report was provided by the Safety Committee of the Water Resources Division.

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