1. The document discusses concepts and methods for measuring stream discharge or flow, including current meters, portable flumes, buckets, and float methods. It provides guidance on selecting the appropriate measurement technique based on factors like depth and velocity. 2. Details are given on taking discharge measurements with current meters and portable flumes, including positioning in the stream and recording field notes. 3. Applications of discharge measurements discussed include calculating pollutant loading, interpreting water quality data, understanding stream hydraulics, and assessing the results of acid reduction projects in streams.

1. 1
CHEMICAL WATER QUALITYCHEMICAL WATER QUALITY
ASSESSMENTASSESSMENT
Day 2,Day 2, 2009:2009:
Discharge Concepts and MeasurementDischarge Concepts and Measurement
Ohio’s Volunteer Monitoring Training Program
Ohio Environmental Protection Agency (OEPA),
and
Ohio University’s Voinovich School of Leadership and Public
Affairs
Discharge is the flux of water per unit
time moving past a fixed point…
Dimensions ~ volume / time
Units ~ cubic feet / second (cfs)
gallons / minute (gpm)
cubic meters / second (cms)
Importance of Measuring Discharge
Calculate pollutant loading / TMDL
implementation
Interpreting water quality data
Understand stream hydraulics in
relation to biology & habitat
Basics of discharge measurements
Continuity of flow: Q = V * A
Q = flow (discharge)
V = average water velocity
A = x-sectional area
The U.S. Geological Survey sets standards for streamflow measurements. These
standards can be found in Measurement and Computation of Streamflow Volume
1, Measurement of Stage and Discharge (USGS WSP 2175).
Instantaneous measurements
Current meters:
mechanical, acoustic,
electromagnetic
Flumes & weirs:
fixed and portable
Bucket & stopwatch
Float method:
measure surface velocity
Method SelectionMethod Selection
• Current meter: wadeable and
non-wadeable streams above
0.3 feet in depth
• Portable flume: small channels and seeps, up to
about 0.8 feet in depth
• Bucket & stopwatch: flow from culverts & pipes
• Float method: when you don’t have a flow
meter; still need to measure channel x-section

2. 2
Current Meters
Price AA meter:
wading rod and bridge crane applications
Current Meter Method Selection
Measure using theMeasure using the
pygmy meterpygmy meter
……measuring flow inmeasuring flow in
water flowing slower thanwater flowing slower than
2.5 feet per second2.5 feet per second
Measure using a bridgeMeasure using a bridge
crane/board and/or thecrane/board and/or the
type AA meter.type AA meter.
……measuring flow inmeasuring flow in
water flowing faster thanwater flowing faster than
2.5 feet per second2.5 feet per second
ThenThenIfIf
Velocity
Current Meter Method Selection
Depth
Use a flume or a bucketUse a flume or a bucket
and stopwatchand stopwatch
...measuring a flow at a...measuring a flow at a
depth of less than aboutdepth of less than about
0.3 feet0.3 feet
The AA meter (down to 1.0The AA meter (down to 1.0
ft depth) or pygmy meterft depth) or pygmy meter
may be used dependingmay be used depending
on the rate of flow, use aon the rate of flow, use a
single point measuring atsingle point measuring at
60% of the depth from the60% of the depth from the
top of the water surface.top of the water surface.
……measuring a flow at ameasuring a flow at a
depth between 0.3 to 2.5depth between 0.3 to 2.5
feetfeet
The AA meter should beThe AA meter should be
used in a twoused in a two--pointpoint
measure at 20% and 80%measure at 20% and 80%
of the total depth. Recordof the total depth. Record
the average of thesethe average of these
recordings as the meanrecordings as the mean
velocity of the verticalvelocity of the vertical
……measuring a flow at ameasuring a flow at a
depth of greater thandepth of greater than
about 2.5 feetabout 2.5 feet
ThenThenIfIf
Current meter set-up showing positions
of the tape and depth/velocity stations
Gordon et al., 2004
Field Notes
Distance from
(width)
Depth
Velocity
(revolutions / time)
Portable flume
• 2.5 to 1000
gpm
• 0.05 to 2.25 cfs
• 1” to 8” throat
• Pack
• Level
• Record depth in
throat

3. 3
Weirs
Gordon et al., 2004
Left: stream profile
Right: stream x-section
Continuous
measurements
•Rely on stage-discharge
relations to
relate stream depth to flow
•Gage records
instantaneous stage
•Discharge is reported in
real time or
statistically summarized and
published
Daily versus peak flow records
Flow regime: seasonality, nature of peaks
Clear Creek near Rockbridge, Ohio
0
200
400
600
800
1000
1200
1400
1/1 1/31 3/2 4/1 5/1 5/31 6/30 7/30 8/29 9/28
Meandailyflow(cfs)
1939-
2006
mean
WY
2006
WY
1988
Flow estimation in streamsFlow estimation in streams
without measurementswithout measurements
• USGS regression equations for mean annual Q
• Drainage-area only equation*
QA = 1.01 A 1.00
• Best-fit equation
QA = 0.17(A)1.01 (Latc – 37)0.26 (Pc –27 )0.62
* Applies to Southeast Ohio, published values by USGS are available for other regions of the state
Manning’s Equation
V = 1.49 R2/3 S1/2 / n
Where:
V = velocity (length/time)
R = hydraulic radius (length) = area / wetted perimeter
S = slope (dimensionless)
n = channel roughness coefficient

4. 4
0.0500.040 - 0.070Steep mountain channels w/ cobble-boulder beds
0.0400.030 - 0.050Steep mountain channels w/ gravel-cobble beds
0.0500.045 - 0.060
Meandering channels w/ high sinuosity and well
developed pools and riffles
0.0400.033 - 0.045
Meandering channels w/ some pool-riffle
development
0.0300.020 - 0.033Straight, clean channels, no meanders
0.015NAClay
0.012NAConcrete
standardrange
Manning's nConditions at the Channel Boundary
Manning’s roughness coefficient, n
Applications
of
Discharge Measurements
Little Raccoon Creek Acid Reduction
0
200
400
600
800
1000
1200
1400
1600
1800
2000
Buffer Run Unnamed Trib - SR124 Mulga Run Middleton Run Flint Run
AMD Project Tributary
lbs/day-AcidLoadReduction
0
10
20
30
40
50
60
70
80
90
100
%ofTotalAcidLoadFromTributary
Acid Load Reduction lbs/day
% Acid Load Reduction
Comparing Loads and/or Load Reductions
LRC Net-Alkalinity Mar 2005 - Jan 2008
0
20
40
60
80
100
120
140
24.55 24.3 22.3 22.15 19.5 18.5 12.71 1.17
Little Raccoon Creek River Mile
Net-Alkalinity(mg/l)
189 cfs 3/7/2005 65 cfs 5/9/2005 8.4 cfs 10/3/2005
300 cfs 2/6/2006 27 cfs 7/17/2006 73 cfs 4/24/2007
9.2 cfs 7/9/2007 31 cfs 1/28/2008 OEPA Net-Alk Target 20 mg/l
Mulga Run
-1321.45
/
Middleton Run
1301.41 lb/day
Goose Run
197.16 lb/day
Buffer Run
305.74 lb/day
Flint Run
995.65 lb/day
St Rt 124 Seep
50.07 lb/day
Average acid loads
at trib mouths
Concentration vs Flow
Flow Duration Curves
Leading Creek TMDL
Simon, Kuhne, & Dickerson, 2002
Establishing Water Quality Targets

5. 5
Questions…?