HomeMy WebLinkAboutDilution Gauging: An Alternative Discharge Measurement2022_WRRI_FamularoDilution Gauging: An Alternative Discharge
Measurement Joe Famularo
Division of Mitigation Services
North Carolina Department of Environmental Quality
Agenda
2
I.History
II.Application
III.Methodology
IV.Limitations
3
3000 B.C.
1500’s
1600’s
1700’s
1900’s
2000’s
Hydrologic Cycle
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Velocity Measurements
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Discharge Measured
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Velocity Gauges
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Early Continuous
Monitoring
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Digital and Remote
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A Brief History of Measuring Stream Discharge
History of Dilution Gauging in Publications
4
•Dilution Gauging –Well Adapted to Mountain Torrents
(Schloesing, 1863)
•Chemical methods of gauging streams (Dumas et al., 1952)
•Gauging Water Flow By the Salt Dilution Method (Hutton &
Spencer, 1960)
•The Gauging of Mountain Streams with Particular Reference to
The Salt Dilution Method (Carter,1963)
•Discharge Measurement in Lower Order Streams (John, 1978)
•Measurement of Discharge using Tracers (Kilpatrick & Cobb,
1985)
Dilution Gauging –What is it?
5
I.Method of discharge measurement where a conservative
tracer (NaCl, rhodamine dye) in dissolved water is added to a
stream and the response is monitored downstream of
addition site.
I.Multiple approaches:
I.Constant rate (AKA plateau method)
II.Slug addition
II.Fundamentally, the approach uses a known value of added
tracer upstream relative to the observed downstream tracer to
determine discharge.
Methods of Direct Discharge Measurement
6
Weir & Volumetric Current Meter &
Doppler Dilution Gauging
7
Weir
•Stable and
effective at long
term monitoring.
•Requires
construction and
maintenance,
restricts
passage.
Velocity -Area
•Relatively quick
and commonly
applied method.
•Seasonal
limitations
depending on
discharge.
Dilution Gauging
•Relatively cheap
and the least
field-intensive.
•Can take a long
time to record
data during low-
discharge
conditions.
8
Weir
•Construction
supplies –
varies
depending on
site
Velocity -Area
•Measuring tape
•Velocity meter
•Top setting
wading rod
Dilution Gauging
•Bucket
•Conservative
tracer
•Conductivity
meter or
fluorometer
9
𝑄=4.28𝐶tan 𝜃
2 (ℎ+𝑘)
5
2
y = 1708.4x5.8086
R² = 0.9891
1.0
10.0
100.0
1000.0
10000.0
0.4
Di
s
c
h
a
r
g
e
(
G
P
M
)
Stage (ft)
Methods of Discharge Measurement: Dilution Gauging
(Constant Rate Injection)
10
11
Dilution Gauging (Constant Rate Injection)
Visualized
Co
n
d
u
c
t
i
v
i
t
y
(
u
s
/
c
m
)
Time (s)
12
Time (s)
Co
n
d
u
c
t
i
v
i
t
y
(
u
s
/
c
m
)
Dilution Gauging (Constant Rate Injection)
Visualized
13
C0
𝑄=𝑞(𝐶1 −𝐶2)
𝐶2 −𝐶0
•Discharge is determined
using:
•Injection rate (q)
•Injection concentration (C1)
•Plateau concentration (C2)
•Background concentration (C0)
Methods of Discharge Measurement: Dilution
Gauging (Constant Rate Injection)
14
0
5
10
15
20
25
9:50:24 9:57:36 10:04:48 10:12:00 10:19:12 10:26:24 10:33:36 10:40:48 10:48:00
Co
n
d
c
t
i
v
i
t
y
Time
Constant Rate vs. Slug Addition
15
Methods of Discharge Measurement: Dilution
Gauging (Slug Injection)
0
5
10
15
20
25
9:50:24 9:57:36 10:04:48 10:12:00 10:19:12 10:26:24 10:33:36 10:40:48 10:48:00
Co
n
d
c
t
i
v
i
t
y
Time
16
Dilution Gauging (Slug Injection) Visualized
Co
n
d
u
c
t
i
v
i
t
y
(
u
s
/
c
m
)
Time (s)
0
5
10
15
20
25
9:50:24 9:57:36 10:04:48 10:12:00 10:19:12 10:26:24 10:33:36 10:40:48 10:48:00
Co
n
d
c
t
i
v
i
t
y
Time
17
•Discharge is determined using:
•Injection mass added (𝑚𝑡𝑟−𝑎𝑑𝑑𝑑𝑑)
•Observed concentration (𝐶𝑇𝑡)
•Background concentration (𝐶0)
Methods of Discharge Measurement: Dilution
Gauging (Slug Injection)
𝑄=𝑚𝑎𝑐𝑐𝑐𝑐
𝑚𝑟𝑐𝑐𝑜𝑣𝑐𝑟𝑐𝑐
=𝑚𝑡𝑟−𝑎𝑐𝑐𝑐𝑐
σ𝑖=1
𝐷𝐶𝑇𝑡−𝐶0 𝑑𝑡
18
Converting Electrical Conductivity to
Concentration
y = 0.0008x -2.6382
R² = 0.9961
-10
0
10
20
30
40
50
60
70
80
90
0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000
Na
C
l
M
a
s
s
Conductivity
𝑄=𝑚𝑎𝑐𝑐𝑐𝑐
𝑚𝑟𝑐𝑐𝑜𝑣𝑐𝑟𝑐𝑐
=𝑚𝑡𝑟
σ𝑖=1𝐷𝐶𝑇𝑡−𝐶0 𝑑𝑡
19
Additional Considerations
•Mixing length (10-20 times channel width; Hudson and Fraser 2002)
•Reduce number of pools for quicker outcomes
•Addition location
•Addition quantity
•Enough to create a downstream signal with sufficient resolution
•Corresponds with mixing length, discharge
•Solute additions can also be used to determine:
•Velocity
•Transit times
•Transient storage
Limitations
•Need sufficient length of reach to promote complete mixing of
solute.
•Can take a long time to return to background concentrations
during low discharge conditions.
•If done incorrectly, could introduce NaCl pulse that is outside of
tolerable range. However, if done correctly, the addition
represents minimal risk of affecting aquatic life (Butterworth et
al.,2007).
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Questions?