Nueces Estuary Hydrology, Hydrodynamics & Salinity

Texas Water Development Board

Bays & Estuaries Program

Carla G. Guthrie, Ph.D.

June 24, 2011

Corpus Christi Bay

Nueces Bay

Oso Bay

Nueces River

Oso Creek

Gulf of Mexico

Aransas Bay

Laguna Madre

Entrance Channel

Gaged

+ Modeled

+ Return

- Diversion

= Surface Inflow

Coastal Hydrology

Version Date

Range

Gaged

Flows

Ungaged

Flows Diversions Returns

TWDB201004 1941-2009 1941-2009 1941-2009

1941-2009

*Missing data for

11/2005 – 12/2006

1941-2009

TWDB201101 1941-2009 1941-2009 1941-2009

1941-2009

*addtl’ NRA/HDR

2000-2009

1941-2009

*addtl’ NRA/HDR

2000-2009

Appendix A, Page 17 – Nueces Hydrology Report

Hydrology Applied to TxBLEND

Figure 8, Page 12 – Nueces Hydrology Report

Copano Bay

Gulf of Mexico

Aransas Bay

Nueces Bay

CorpusChristi Bay

Oso Bay

LagunaMadre

Baffin Bay

NuecesRiver

Physical Description

• 2-D, vertically-averaged

• Finite Element model

• Unstructured grid, with

triangular elements

S8HH.f Current Version of TxBLEND

• Shallow water equations

(generalized wave continuity eq.

and momentum eq.)

• Advection-Diffusion eq. for salinity

transport

TxBLEND

What goes into the model?

Physical Description

Computational Mesh/Grid

Bathymetry

Bottom Drag

Time Varying Boundary Conditions

Rivers (Inflows, Loads)

Tidal Elevations

Wind Speed & Direction

Evaporation & Precipitation

Salinity

Salt/CavassoCreeks

CopanoCreekMission

River

AransasRiver

NuecesRiver

OsoCreek

San FernandoCreek

• Water Surface Elevation

• x- & y- components of Velocity

• Concentration (Salinity)

At each

computational node

for each time step

Copano Bay

Gulf of Mexico

Aransas Bay

Nueces Bay

CorpusChristi Bay

Oso Bay

LagunaMadre

Baffin Bay

NuecesRiver

What is the model output?

TxBLEND Nueces Estuary Model

Model Calibration

Velocity and Discharge: 1994, 1995, 2000

Salinity: 4 locations, variable periods between 1987 - 2004

CC ShipChannelnear B&R

HumbleChannel

GIWW nearJFK Causeway

Habor Bridge

Oso Bay at Bridge

Nueces Causewayin channel

GIWW nearBird Island

GIWW nearPita Island

Nueces Causewayoff channelNueces Causewayoff channel

CC Channelnear Ingleside

Lydia AnnChannel

AransasChannel

EntranceChannelnear UTMSI

Point ofMustang

Velocity & Discharge Measurements

Intensive inflow studies 1994, 1995, 2000

- Three intensive inflow studies:

Velocity: June 1994, 1995

Discharge: June 1994, 1995, May 2000

-14 locations

- Simulated velocities were generally

representative at all sites

- Simulated discharge was generally

representative (both in magnitude and

direction)

- Some instances of over- or under-

prediction

Intensive inflow studies 1999 – 2004

Rockport

Packery Channel

White Point

Port Aransas

Bird Island

Texas StateAquarium

Ingleside

Bob HallPier

Tide Gaging & Surface Elevation

- Eight locations (1999 – 2004)

- r2 ranged 0.78 to 0.96

- Captures Gulf exchange

- Some missing data in plots

- Captures storm surge

- Generally predicts water elevation, tidal

phase and amplitude

Aransas Bay

GIWW nearJFK Causeway

Nueces Bay

CorpusChristi Bay

Mid-Aransas Bay 1987 - 1989

Nueces Bay 1987 - 1989, 2000 - 2004

Corpus Christi Bay 1987 - 1989, 2000 - 2004

GIWW-JFK Causeway 1991 - 1996

Gulf Salinity Boundary TPWD CF data

Long-Term Salinity Measurements

- Four locations

- r2 ranged 0.14 to 0.91

- Difference btwn mean and observed

salinity at a site is <2 ppt

- Some erroneous data included in plots

- Generally captures trends, but misses

high-frequency variation in salinity

- At times over- or under-predicts salinity

by several ppt.

Observed Daily Salinity (ppt)S

imu

late

dD

aily

Sa

lin

ity

(pp

t)

0 10 20 30 400

10

20

30

40

Nueces Bay 1987-1989

Simulated and Observed Nueces Bay Salinity (1987 – 1989)

Days r2

RMS

(ppt)

Nash-

Sutcliffe

Average Salinity

(ppt)

DiffSal Model Obs.

853 0.82 4.4 0.79 30.4 30.2 +0.2

Figures 45 – 46, Page 49

Table 5, Page 53

Simulated and Observed Nueces Bay Salinity (2000 - 2004)

Days r2

RMS

(ppt)

Nash-

Sutcliffe

Average Salinity

(ppt)

DiffSal Model Obs.

1,413 0.91 3.8 0.90 19.4 20.2 -0.8

Figures 47 – 48, Page 50

Table 5, Page 53 Observed Daily Salinity (ppt)

Sim

ula

ted

Da

ily

Sa

lin

ity

(pp

t)

0 10 20 30 400

10

20

30

40

Nueces Bay 2000-2004

Simulated and Observed Salinity

Figure 41, Page 47

Figure 49, Page 51

TxBLEND Nueces Estuary Model

Model Validation

Salinity: 4 locations, variable periods between 1994 - 2009

Aransas Bay

GIWW nearJFK Causeway

Nueces Bay

CorpusChristi Bay

Mid-Aransas Bay 1994 - 2000

Nueces Bay 2005 - 2009

Corpus Christi Bay 2005 - 2009

GIWW-JFK Causeway 1997 - 2002

Long-Term Salinity Measurements

- Four locations

- r2 ranged 0.30 to 0.84

- Difference btwn mean and observed

salinity at a site is <2 ppt

- Generally captures trends, but misses

high-frequency variation in salinity

- At times over- or under-predicts salinity

by several ppt.

- Provides general idea of salinity

conditions when observed data is lacking

Simulated and Observed Nueces Bay Salinity (2005 – 2009)

Days r2

RMS

(ppt)

Nash-

Sutcliffe

Average Salinity

(ppt)

DiffSal Model Obs.

1,328 0.84 4.3 0.79 26.8 25.0 +1.8

Figures 59 – 60, Page 58-59

Table 5, Page 53 Observed Daily Salinity (ppt)

Sim

ula

ted

Da

ily

Sa

lin

ity

(pp

t)

0 10 20 30 400

10

20

30

40

Nueces Bay 2005-2009

spare slides

Hydrodynamic & Salinity Transport Model

(TxBLEND)

Purpose

Provide simulation and representation of water currents and

salinity distribution throughout the bays

Why?

Allows for modeling scenarios of changing inflows, climate, or

physical geometry to predict effects on salinity and circulation

patterns within the bay

Simulated and Observed Velocities (June 21 – 24, 1994)

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7Vel-5/10

SimuVel

Entrance Channel

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7Vel-5/10

SimuVel

C C Channel near B&R

June 1994

Ve

locit

y(f

ps)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7 Vel-8/10

Vel-5/10

Vel-2/10

SimuVel

Point of Mustang

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7Vel-5/10

SimuVel

Entrance Channel

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7Vel-5/10

SimuVel

C C Channel near B&R

June 1994

Ve

locit

y(f

ps)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7 Vel-8/10

Vel-5/10

Vel-2/10

SimuVel

Point of Mustang

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-8/10

Vel-5/10

Vel-2/10

SimuVel

C C Channel near Ingleside

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6Vel-8/10

Vel-5/10

Vel-2/10

SimuVel

Nueces Causeway in the channel

June 1994

Ve

locit

y(f

ps)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6Vel-8/10

Vel-5/10

Vel-2/10

SimuVel

Nueces Causeway off the channel

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

GIWW near JFK Causeway

June 1994

Ve

locity

(fp

s)

21 22 23 24 25-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

Humble Channel

Simulated and Observed Velocities (June 12 – 15, 1995)

June 1995

Ve

locit

y(f

ps)

11 12 13 14 15 16-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

Lydia Ann Channel

June 1995

Ve

locity

(fp

s)

11 12 13 14 15 16-7

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7 Vel-5/10

SimuVel

Entrance Channel

June 1995

Ve

locit

y(f

ps)

11 12 13 14 15 16-7

-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6

7 Vel-5/10

SimuVel

C C Channel near B&R

June 1995

Ve

locity

(fp

s)

11 12 13 14 15 16-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

Aransas Channel

June 1995

Ve

locity

(fp

s)

11 12 13 14 15 16-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

Nueces Causeway off channel

June 1995

Ve

locity

(fp

s)

11 12 13 14 15 16-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-8/10

Vel-5/10

Vel-2/10

SimuVel

Nueces Causeway in channel

June 1995

Ve

locit

y(f

ps)

11 12 13 14 15 16-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

Oso Bay at Bridge

June 1995

Ve

locity

(fp

s)

11 12 13 14 15 16-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

GIWW near JFK Causeway

June 1995

Ve

locit

y(f

ps)

11 12 13 14 15 16-6

-5

-4

-3

-2

-1

0

1

2

3

4

5

6 Vel-5/10

SimuVel

Humble Channel

Simulated and Observed Tidal Elevations (1997-1999)

Manning’s n (bottom roughness) Coefficient

ManN

0.050

0.048

0.045

0.043

0.040

0.038

0.036

0.033

0.031

0.028

0.026

0.024

0.021

0.019

0.016

0.0209

0.0202

0.0211

0.0333

0.031

0.0162

0.0201

0.0181

0.0211

0.0163

0.0194

Dispersion Coefficient

Disp

20000

18600

17200

15800

14400

13000

11600

10200

8800

7400

6000

4600

3200

1800

400

218

201

180

225

20000

501

466

177

19000

500