This presentation was made at the 2012 ASCE-EWRI Hydraulic Measurement and Experimental Methods conference in August 2012 at Snowbird, Utah. The presentation describes the spatial variability of surface water characteristics at Big Creek Lake during a four-week study in October 2011. These data were collected as part of Dr. Whelton and Dr. Webb\'s Field Analysis and Sampling Techniques in Civil Engineering (FAST CE) course.

1. Flow & Water Quality Monitoring II HMEM 2012
Near-Synoptic Measurements of
Surface Water Characteristics in a
Reservoir using a Personal
Watercraft-based Mapping System
Bret M. Webb, Ph.D.
Andrew J. Whelton, Ph.D.
University of South Alabama, Department of Civil Engineering

2. Presentation Outline HMEM 2012
• Motivation
• Study Area
• Experimental Design
• PWC System
• Results
• Conclusions
• Future Work
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3. Motivation HMEM 2012
Where is the TOC
• Local utility facing
coming from? tougher EPA standards
DBP: Disinfection Byproduct • Disinfection byproducts
TOC: Total Organic Carbon
DOC: Dissolved Organic Carbon • Regulation of TOC at raw
POC: Particulate Organic Carbon
water source
“DBPs are formed when
disinfectants used in water
treatment plants react with
• Additional treatment
natural organic matter in the
source water. Different
• Prior investigations
disinfectants produce different
types or amounts of DBPs… • Tributary influence
including trihalomethanes,
haloacetic acids, bromate, and • Spatial variability of WQ
chlorite.”
--USEPA
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4. Study Area HMEM 2012
Big Creek Lake @ • Impounded 1952
J.B. Converse
Reservoir • Raw water source for 300,000
Mobile Co.
• 7 tributaries, 3 of which account
for 72% of inflow
• Volume: 64,000,000 m3
• Area: 13 km2
• Watershed: 267 km2 (87% rural)
• Qavg: 4.6 m3/s
• Davg: 4.4 m
• Tr: 160 days
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5. Experimental Design HMEM 2012
• Stream gaging (3 sites)
• Water sampling (7 sites)
Hamilton Creek Arm – At surface
An aggressive four-week field – At depth (Niskin bottle)
campaign was completed in
October 2011 with the help of four – Handheld: T, pH, DO, TU
graduate and two undergraduate
students, as well as employees of • Vertical profiling (4 sites)
the water utility.
– SeaBird SBE 25
Data collection performed – YSI CastAway CTD
simultaneously using three teams:
1) boat, 2) Jag Ski, 3) stream • ADCP profiling (4 sites)
Data collection always performed
• Comprehensive surface WQ mapping
in afternoon • Analysis (7 sites)
No precipitation during study – TN, TP, TOC
period
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6. Experimental Design HMEM 2012
A B
C
PSI
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7. PWC-based Mapping System HMEM 2012
South Alabama
Jag Ski
• SonTek M9 ADCP
• YSI Portable SeaKeeper
– YSI 6600v2-4 sonde
– Turner Designs C3
• YSI CastAway CTD
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8. PWC-based Mapping System HMEM 2012
PWC Mapping
Overview
The PSK system analyzes water
continuously, but only reports a
sample about every 10 seconds
Each sample is automatically geo-
referenced and synchronously
saved to the onboard computer
ADCP surveys were conducted
first, then the study area was
covered at high speed ~15 m/s
Each deployment was completed in
~2 hours
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9. PWC-based Mapping System HMEM 2012
PWC Mapping
Overview
Parameters measured:
Temperature
Conductivity
pH
Dissolved Oxygen
Turbidity
Chlorophyll-a
Colored Dissolved Organic Matter
Crude Oil
Refined Fuels
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10. Results HMEM 2012
• Study results:
Overview – Results consistent
Some data show a statistical
significance between the WQ east
– Lake generating TOC
and west of the raw water intake
• PWC-based results:
Relationship of WQ for Hamilton
Creek and raw water intake is – Comparison to other
inconclusive for most parameters
methods
WQ characteristics at raw water
intake likely constitutes a mixture – Statistical segregation of
of water to its east and west, but
influence of Hamilton Creek is study area
clear for some parameters
– Comprehensive WQ
TOC values statistically similar
within lake, but unique from mapping
streams
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11. Results HMEM 2012
Device Inter-comparison – October 2011
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12. Results HMEM 2012
Spatial Variability of WQ – October 2011
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13. Results HMEM 2012
Temperature - October 10, 2011
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14. Results HMEM 2012
Temperature - October 10, 2011
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15. Results HMEM 2012
Temperature – October 2011
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16. Results HMEM 2012
Specific Conductivity – October 2011
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17. Results HMEM 2012
Specific Conductivity – October 24, 2011
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18. Results HMEM 2012
Chlorophyll-a – October 2011
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19. Results HMEM 2012
CDOM – October 2011
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20. Results HMEM 2012
pH – October 2011
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21. Results HMEM 2012
Dissolved Oxygen – October 2011
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22. Results HMEM 2012
Turbidity– October 2011
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23. Conclusions HMEM 2012
• Base flow conditions
• Method agreement
• Statistical significance
east/west
• Conductivity always
significantly higher @
Hamilton Creek
• Lake generates TOC
• Intake water exhibits
characteristics of
east/west WQ
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24. Future Work HMEM 2012
Spatial Mapping of
TOC/DOC
Future work at Big Creek
Lake will focus on
developing a calibration
curve that relates CDOM
to TOC at the site.
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25. Closing HMEM 2012
Acknowledgments
Dr. Andrew Whelton
Richard Allen, Bennett Dulaney,
Craig Erdman, Iryna Lucas, Chris
Marr, and J. Kane Thomley
MAWSS
The National Science Foundation
(OCE-1058018)
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