Texas Bay and Estuary Study Program

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WMHS 602 February 8, 2006
Texas Bay and Estuary Study Program
Cindy Loeffler, Chief Water Resources Branch
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Freshwater Inflows
Salinity
Nutrients
By Definition Create and Sustain Estuaries
Sediments
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TWC Section 11.147
Defines Beneficial Inflows As the Salinity,
Nutrient, and Sediment Loading Regime Adequate to
Maintain an Ecologically Sound Environment in the
Receiving Bay and Estuary System That Is
Necessary for the Maintenance and Productivity of
Economically Important and Ecologically
Characteristic Sport or Commercial Fish and
Shellfish Species and Estuarine Life Upon Which
Such Fish and Shellfish Are Dependent.
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The Process of Developing FWI Recommendations
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FWI Recommendations Are Based on the Biological
Needs of a Group of Target Species Expressed As A
Statistical Relationship Between Harvest or
Catch per Unit Effort And Inflow
H 110.64 145.3ln(Qjf) 332.5ln(Qja)
141.4ln(Qso) H 3000.7 180.4ln(Qma)
963.3ln(Qmj) 710ln(Qja) - 231.5ln(Qso) H
32.786 0.0797Qmj 0.2750Qja
0.2010Qnd H -18.087 0.2411Qjf
0.1734Qma 0.0850Qnd ln(H) 2.6915
0.7185ln(Qma) 1.86ln(Qmj)
1.086ln(Qnd) ln(H) 6.5679
0.6707ln(Qja) 0.7486ln(Qso) H 545.59
160.9ln(Qjf) 279.1ln(Qmj) 155.1ln(Qja)
- 277.9ln(Qnd)
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TPWD and TWDB Have Jointly Developed FWI
Recommendations To Maintain the Health and
Productivity of Texas Estuaries
TxEMP Is The Optimization Model That Produces a
Range Of Inflows Within Which Estuarine Health
and Productivity Needs May be Met
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A Range Of Possible Solutions Lies Between Two
Points Along An Optimization Curve MaxQ and MinQ
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Delivery of Freshwater Inflows Must Incorporate
Seasonality to Have Any Ecological Significance
FWI Seasonal Distribution San Antonio Bay
The Recommended FWI Is Often Expressed As a
Single Annualized Number, But Always Infers The
Sum of Bi-Monthly Inflows
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Summary Methodology to Determine the Freshwater
Inflows Necessary to Meet the Legislative
Directive of TWC Section 11.147
Input Real Data Into Models And Assess Projected
Estuarine Conditions
Create Models That Integrate Datasets and Predict
Response To Varying Freshwater Inflows
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Legislatively Mandated Studies to
Determine Beneficial Inflows Necessary to
Conserve Health and Productivity Of Texas Major
Estuaries Have Been Completed. Some are Being
Updated.
Millions of Acre Feet Per Year
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Case Study
Galveston Bay
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TxEMP MinQ and MaxH Solutions
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TxEMP Monthly Flow Distribution
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TXBLEND Output

• Monthly Salinity Maps Under Each TxEMP Solution
• Salinity Difference Maps
• Spatial Relationships of Modeled Salinity Zones
  to Critical Habitat Areas

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White Shrimp Abundance in Galveston Bay

• Higher abundance correlates with lower salinity
  levels

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Galveston Bay TXBLEND Time Series

• Daily salinity at a point in Upper Galveston Bay
• Predicted salinity within upper and lower limits
  for MaxH and MinQ

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TxEMP MinQ and MaxH Solutions
TPWD Recommendation
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Comparison of Model Solutions to Historical
Inflows
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Reviews
Methods for Determining Minimum Freshwater Inflow
Needs of Texas Bays and Estuaries - Powell,
Matsmuto, Brock. In Estuaries December 2002.
Nowhere in the World Has the Issue of Freshwater
Inflow Been Studied So Systematically, or The
Results Used to Guide Water Management Policies
and Practices So Effectively, Than in the State
of Texas. A Review and Application of
Literature Concerning Freshwater Flow Management
in Riverine Estuaries (2000), by Dr. E. Estevez,
Director, Center for Coastal and Tropical
Ecology, Mote Marine Laboratory, Sarasota,
Florida.
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Reviews
While the State of Texas has pioneered tools to
address freshwater inflow needs for bays and
estuaries, there are limitations to these tools
in light of both scientific and public policy
evolution. Science Advisory Committee to the
Study Commission on Water for Environmental
Flows, Interim Report to the 79th Legislature,
December 2004
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Summary of SAC BE comments

• Incorporate stakeholder input/peer review
• Commercial vs. independent fisheries data
• Improve statistical methods
• TPWD Verification analysis
• Optimum inflow vs. drought conditions
• Adaptive management and precautionary
  principle methods

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