1. Modeling Dissolved Oxygen Concentration in Lavaca Bay CE 394K – GIS in Water Resources Instructor  Dr. David Maidment Term Project by Jeffrey G. Baguley Fall 2000

2. Overview Hypoxia and its Effects on Benthic Fauna Statistical Analysis  Expected Dissolved O 2 Levels Goals of Project ArcView Modeling Problems and Further Goals

3. Hypoxia Hypoxia  A condition in which oxygen is a limiting factor in the environment. In Texas Bays this has been defined as a dissolved oxygen concentration of 3 mg/L or less. Causes 1.Water column stratification (layers of differing densities) 2.Increased biological respiration 3.Decomposition of Organic Matter 4.Sulfide Conditions

4. Factors Facilitating Hypoxia in Texas Bays Summer Tidal Mixing Freshwater Inflow Salinity Water Column Stratification Isolated Bottom Water Hypoxia Water Temp. Gas Solubility Biological Respiration

5. Macroinfaunal Response to Hypoxia Ritter and Montagna (1999) Determined: Community: Diversity  reduced 500% Abundance  reduced 500% Biomass  reduced 1200% Polychaete (P. Annelida)

6. Expected Seasonal DO Values Multiple regression analysis  MS Excel Fourier Series is of the form: t = Julian days y = DO conc. a,b = coefficients from regression j = # of cycles within time period  = 2  /365

7. Goals 1.Model spatial variation  How dissolved O 2 changes from location to location. 2.Model temporal variation  Annual trends within Lavaca Bay.

8. Previous Spatial Modeling (Ritter and Montagna 1999)

9. The Study Area Shapefile of study area obtained from NHD Dataset HUC code 12100402

10. Creating Point Shapefile

11. Spatial Modeling ArcView Extension  Spatial Analyst Contour lines Grid TIN Interpolated from DO values for each station

12. Spatial Modeling Using Grids Average Spring Values Hypoxic Zone

13. Temporal Modeling  Creating an Animated GIF File –GIF Construction Set Professional TM Free Download

14. Problems and Future Work Inadequate data Focus on a smaller scale What can be done to prevent hypoxia?

15. Acknowledgements Dr. Paul Montagna (UTMSI) Data and Guidance Mike Veazey (TNRCC) Data Dr. Maidment (CRWR) Fourier Analysis