National Park Service U.S. Department of the Interior Water Resources Division Natural Resource Program Center ASSESSMENT OF COASTAL WATER RESOURCES AND WATERSHED CONDITIONS AT PADRE ISLAND NATIONAL SEASHORE, TEXAS Kim Withers, Elizabeth Smith, Olivia Gomez, and John Wood Technical Report NPS/NRWRD/NRTR-2004/323 The National Park Service Water Resources Division is responsible for providing water resources management policy and guidelines, planning, technical assistance, training, and operational support to units of the National Park System. Program areas include water rights, water resources planning, regulatory guidance and review, hydrology, water quality, watershed management, watershed studies, and aquatic ecology. Technical Reports The National Park Service disseminates the results of biological, physical, and social research through the Natural Resources Technical Report Series. Natural resources inventories and monitoring activities, scientific literature reviews, bibliographies, and proceedings of technical workshops and conferences are also disseminated through this series. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the National Park Service. Copies of this report are available from the following: National Park Service (970) 225-3500 Water Resources Division 1201 Oak Ridge Drive, Suite 250 Fort Collins, CO 80525 National Park Service (303) 969-2130 Technical Information Center Denver Service Center P.O. Box 25287 Denver, CO 80225-0287 Assessment of Coastal Water Resources and Watershed Conditions at Padre Island National Seashore, Texas Kim Withers, Elizabeth H. Smith, Olivia Gomez, and John Wood Center for Coastal Studies Texas A&M University-Corpus Christi 6300 Ocean Drive Corpus Christi, Texas December 2004 This work was accomplished under Task Order J2380 03 0239 of Cooperative Agreement 50000 03 055 of the Gulf Coast Cooperative Ecosystems Study Unit ii iii TABLE OF CONTENTS Page LIST OF FIGURES............................................................................................................ vi LIST OF TABLES.............................................................................................................. ix EXECUTIVE SUMMARY................................................................................................ xii ACKNOWLEDGEMENTS............................................................................................... xvii INTRODUCTION…........................................................................................................... 1 PARK DESCRIPTION….................................................................................................. 4 Physical Setting & Key Features…....................................................................... 4 Land Use & Population …..................................................................................... 7 Coastal Development........................................................................................... 7 Conservation Areas within PAIS Project Area ................................................... 11 Wastewater Treatment Plants & Landfills ......................................................... 12 Oil and Gas Activity within PAIS ....................................................................... 12 Hydrology................................................................................................................ 15 Hydrologic Unit Areas (HUA) for PAIS Project Area ........................................ 15 Hydrology & Sources of Fresh Water ................................................................ 15 Hydrologic Dynamics & Effects of Alterations .................................................. 17 Trends in Surface & Groundwater Withdrawals ................................................ 19 Alterations of PAIS Hydrology or Hydrodynamics Attributable to Water Use ............................................................................................................ 20 Biological Resources: Overview of Habitats & Associated Flora & Fauna....................................................................................................................... 21 Beach .................................................................................................................. 21 Sea Turtles ..................................................................................................... 23 Red Tide ......................................................................................................... 24 Dunes and Vegetated Flats ................................................................................. 25 Inland Waters ...................................................................................................... 26 Tidal Flats and Salt Marshes .............................................................................. 27 Seagrass .............................................................................................................. 37 Changes in Seagrass Community Composition ............................................. 38 Seagrass Scarring ........................................................................................... 39 Commercial and Recreational Fisheries ............................................................ 40 Exotic or Invasive Species .................................................................................. 43 WATER QUALITY ASSESSMENT............................................................................... 46 Water Quality Standards...................................................................................... 46 iv Page Available Water Quality Data.............................................................................. 46 Legacy STORET .................................................................................................. 46 Database Development & Management ........................................................ 51 Freshwater Stations ....................................................................................... 53 Estuarine Composite Stations ........................................................................ 54 Estuarine Single Stations ............................................................................... 57 Texas Commission on Environmental Quality (TCEQ) Data ............................ 64 Geographic Area Designations for Assessing & Monitoring Water Quality.................................................................................................. 64 Data Description & Summary ....................................................................... 67 National Coastal Assessment Program (NCA) ................................................... 73 Regional Coastal Assessment Program (RCAP) ................................................ 76 Trash .................................................................................................................. 76 Assessment Summary and Identification of Data Gaps..................................... 84 Fresh Waters........................................................................................................ 84 Estuarine Waters.................................................................................................. 84 Gulf of Mexico...................................................................................................... 86 CONCLUSIONS & RECOMMENDATIONS................................................................. 87 Evaluation of the Current State of Knowledge................................................... 87 Recommendations for Monitoring....................................................................... 89 Estuarine Waters.................................................................................................. 89 Seagrasses....................................................................................................... 90 Circulations & Dredge Material Placement.................................................... 90 Fresh (Inland) Waters......................................................................................... 90 Wetlands......................................................................................................... 91 Groundwater........................................................................................................ 92 Nearshore Marine Waters.................................................................................... 92 Invasive or Exotic Species................................................................................... 92 LITERATURE CITED..................................................................................................... 93 v LIST OF FIGURES Figure Page 1 Map showing Padre Island National Seashore and surrounding areas....... 2 2 Boundaries of Padre Island National Seashore and their relationship to the surrounding area................................................................................... 5 3 Profile of Padre Island showing general topography and physiography (from Smith 2002)...................................................................................... 6 4 Historical overview of development on North Padre Island adjacent to Packery Channel and Gulf Intracoastal Waterway (GIWW) from a) 1956, b) 1967, c) 1968, and d) 1995.......................................................... 9 5 Padre Island National Seashore boundaries (in red) and associated conservation lands owned