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Salinity Intrusion: Integrating Riverine and Coastal Forces
Paul Conrads U. S. Geological Survey SC Water Science Center
Columbia, SC
NIDIS Carolinas Pilot Project Scoping WorkshopJuly 31, 2012
Outline
Conceptual model of salinity intrusion
Look at some data Drought and salinity intrusion Coastal drought index and data
resource Summary
Short Review Salinity Dynamics
Freshwater
SaltwaterRiverine
Flow
Tidal Forcing mean water level, tidal range
“…estuaries may never really be steady-state systems; they may be trying to reach a balance they never achieve.”
Keith Dyer, from Estuaries – A Physical Introduction (1997)
Saltwater-Freshwater Interface
High flowsLow water
levels
Tidal MarshesCritter Communities
Saltwater-Freshwater Interface
Low flowsHigh water
levels
Tidal MarshesCritter Communities
Example of Data: Yadkin-Pee Dee Basin
Freshwater
SaltwaterRiverine
Flow
Tidal Forcing mean water level, tidal range
Flow: Pee Dee River at Pee Dee
Water level and Tidal Range: Atlantic Intracoastal Waterway at Little River Inlet
Specific conductance (salinity): Waccamaw River the Hagley Landing
Example of Data: StreamflowFreshwater
SaltwaterRiverine
Flow
Tidal Forcing mean water level, tidal range
Example of Data: Water levelFreshwater
SaltwaterRiverine
Flow
Tidal Forcing mean water level, tidal range
Two signals:Mean water level & Tidal Range
Tide Range
Mean Water Level
Water Level and Tidal Range
Pee Dee River Flows
Waccamaw River Specific Conductance
Flows and Specific Conductance
SP
EC
IFIC
CO
ND
UC
TAN
CE
, UG
/CM
an
d F
LO
W, F
T3 /
S
GA
GE
HE
IGH
TS
AN
D F
ILT
ER
ED
GA
GE
S H
EIG
HT,
FE
ET
Converging Conditions
Looking Inside the Black Box
3D response surfaces Surface created by
model “Unseen” variables
set to constant value
Manifestation of historical behavior of system
Insight to the process dynamics or physics
What Conditions Cause Large Intrusions?
High water
Low water
3-D Response surface – Flow, Tidal Range, and Salinity
Sal
inity
>
Sal
inity
>
Flow >
Flow >
Tide range >
Tide range >
Low Coastal Water Level High Coastal Water Level
Savannah River
Riverine Flows
Savannah River at Clyo
Tidal Forcing
Mean Water level
Tidal RangeFort Pulaski
FreshwaterSaltwater
Specific conductance
I-95
Savannah River at I-95
Converging Conditions:Savannah River
Flow and Drought Index
Very quick look at South Carolina Coast
Weekly drought index for Marion County
Plot with 7-day average flow & 7-day average specific conductance
Flow and Drought IndexD4
D3
D2
D1
0-D0
Specific Conductance and Drought Index
D4
D3
D2
D1
0-D0
Data Resource – USGS Real-time Network
USGS Coastal Carolina Real-time Network
~50 active gages:
Parameters: water level, sp. cond., temperature, dissolved oxygen, turbidity, pH, and/velocity
Summary
Salinity dynamics results of flow and coastal water interaction
Salinity intrusion events caused by convergence of conditions
Potential of a salinity coastal drought index
Real-time data networks available to support potential coastal drought index
Fast Forward
FERC Re-licensing
AIW/North End Salinity
Example of Data: StreamflowFreshwater
SaltwaterRiverine
Flow
Tidal Forcing water level, tidal range
Convergence of Conditions
Orbital Mechanics and Tide Range
Neap Tides Spring Tides
Tidal Range and Specific Conductance
Water Level and Specific Conductance
Converging Conditions:South End – Waccamaw River
