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Residence Times in Texas Bays: 1975 - 2000

Residence Times in Texas Bays: 1975 - 2000. Laura Chu UT Marine Science Institute CE 394K – Surface Water April 26, 2005. Background. Residence time Why Study Inflows? Climate change Water Balance in Texas Constant vs. “flashy” system. Residence Time.

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Residence Times in Texas Bays: 1975 - 2000

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  1. Residence Times in Texas Bays: 1975 - 2000 Laura Chu UT Marine Science Institute CE 394K – Surface Water April 26, 2005

  2. Background • Residence time • Why Study Inflows? • Climate change • Water Balance in Texas • Constant vs. “flashy” system

  3. Residence Time • Estimate of the rate at which a volume of water moves through a bay. • Several methods to compute • Tidal-Prism method • Freshwater Fraction method

  4. Tidal Prism Method • Method based on changes in estuarine volume due to tides INSUFFICENT DATA • Officer (1976)

  5. Fresh-Water Fraction Method • Uses the salinity to calculate the residence time. • Assumptions • Hydrography • Constant bay volume

  6. Hypothesis • Ho1: Variation in freshwater inflows does not change the turnover time for Texas Bays • Ho2: El Niño has no effect in changing the rate of turnover in Texas Bays

  7. Inflows Monthly for 6 bays & estuaries TXWDB: 1941-2000 Salinity Monthly on a grid TXPWD: 1975 – present Volume of water CRWR – G. Ward El Niño SOI index Estuaries & Bays Sabine Trinity / Galveston Guadalupe / San Antonio Lavaca / Matagorda Mission - Aransas Nueces/Corpus Christi Data

  8. Methodology Salinity Water Balance Bay Volumes Residence Time Equations SOI Index Analyze data Hydrography GIS mapping

  9. Residence Times and Latitude

  10. North – South Differences

  11. SOI Index Values

  12. Effects of El Niño on Residence Times

  13. Some Conclusions • Seasonal freshwater inflows drive changes in residence times in Texas • Hypersaline conditions • No overall long-term trend • No significant El Niño effects

  14. Future Work & Questions • Relating inflow modeling to species abundance and ecosystem health • Effects of hydrography • Visualizing data in GIS • Implications for controlled flow regimes

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