Review of the
Edwards Aquifer Habitat
Conservation Plan
REPORT 1
Committee to Review the Edwards Aquifer Habitat Conservation Plan
Water Science and Technology Board
Division on Earth and Life Studies
NATIONAL RESEARCH COUNCIL
OF THE NATIONAL ACADEMIES
THE NATIONAL ACADEMIES PRESS
Washington, D.C.
THE NATIONAL ACADEMIES PRESS 500 Fifth Street, NW Washington, DC 20001
NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competences and with regard for appropriate balance.
Support for this study was provided by the Edwards Aquifer Authority under Contract No. 13-666-HCP. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.
International Standard Book Number-13: 978-0-309-36887-2
International Standard Book Number-10: 0-309-36887-1
Cover credit: Cover image courtesy of Laura J. Ehlers.
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THE NATIONAL ACADEMIES
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COMMITTEE TO REVIEW THE EDWARDS
AQUIFER HABITAT CONSERVATION PLAN
DANNY D. REIBLE, Chair, Texas Tech University, Lubbock
JONATHAN D. ARTHUR, Florida Department of Environmental Protection, Tallahassee
M. ERIC BENBOW, Michigan State University, East Lansing
ROBIN K. CRAIG, University of Utah, Salt Lake City
K. DAVID HAMBRIGHT, University of Oklahoma, Norman
ANDREW J. LONG, U.S. Geological Survey, Rapid City, South Dakota
TIMOTHY K. KRATZ, University of Wisconsin, Madison
LAURA MURRAY, University of Maryland, Cambridge
JAYANTHA OBEYSEKERA, South Florida Water Management District, West Palm Beach
KENNETH A. ROSE, Louisiana State University, Baton Rouge
LAURA TORAN, Temple University, Philadelphia, Pennsylvania
GREG D. WOODSIDE, Orange County Water District, Fountain Valley, California
NRC Staff
LAURA J. EHLERS, Study Director, Water Science and Technology Board
MICHAEL J. STOEVER, Research Associate, Water Science and Technology Board
WATER SCIENCE AND TECHNOLOGY BOARD
GEORGE M. HORNBERGER, Chair, Vanderbilt University, Nashville, Tennessee
EDWARD J. BOUWER, Johns Hopkins University, Baltimore, Maryland
YU-PING CHIN, Ohio State University, Columbus
DAVID A. DZOMBAK, Carnegie Mellon University, Pittsburgh, Pennsylvania
M. SIOBHAN FENNESSY, Kenyon College, Gambier, Ohio
BEN GRUMBLES, U.S. Water Alliance, Washington, District of Columbia
GEORGE R. HALLBERG, The Cadmus Group, Inc., Boston, Massachusetts
CATHERINE L. KLING, Iowa State University, Ames
DEBRA S. KNOPMAN, RAND Corporation, Arlington, Virginia
LARRY LARSON, Association of State Floodplain Managers, Madison, Wisconsin
RITA P. MAGUIRE, Maguire and Pierce, LLP, Phoenix, Arizona
DAVID I. MAURSTAD, OST Inc., McLean, Virginia
ROBERT SIMONDS, The Robert Simonds Company, Culver City, California
FRANK H. STILLINGER, Princeton University, New Jersey
MARYLYNN V. YATES, University of California, Riverside
JAMES W. ZIGLAR, SR., Van Ness Feldman, Potomac, Maryland
Staff
JEFFREY W. JACOBS, Director
LAURA J. EHLERS, Senior Staff Officer
STEPHANIE E. JOHNSON, Senior Staff Officer
EDMUND DUNNE, Staff Officer
M. JEANNE AQUILINO, Financial/Administrative Associate
ANITA A. HALL, Senior Program Associate
MICHAEL J. STOEVER, Research Associate
BRENDAN R. MCGOVERN, Senior Project Assistant
Preface
The nation’s groundwater is a precious resource that is sensitive to overuse, drought, and contamination. In many areas of the country the population depends upon that resource for water to drink, water to grow food, and water to support the commercial and industrial activities that drive the economy. Ecosystems also depend upon that resource, particularly where surface waters and groundwaters are closely linked. At times there is competition between human and ecological needs for those waters and it is difficult to balance their competing interests.
The Edwards Aquifer in south-central Texas is just such a groundwater resource. It is the primary source of water for one of the fastest-growing cities in the United States, San Antonio, and it also supplies irrigation water to thousands of farmers and livestock operators. The Edwards Aquifer also is the source water for several springs and rivers, including the two largest freshwater springs in Texas that form the San Marcos and Comal Rivers. The unique habitat afforded by these spring-fed rivers has led to the development of species that are found in no other locations on Earth. Due to the potential for variations in spring flow caused by both human and natural causes, these species are continuously at risk and have been recognized as endangered under the federal Endangered Species Act (ESA). In an effort to manage the river systems and the aquifer that controls them, the Edwards Aquifer Authority (EAA) and stakeholders have developed a Habitat Conservation Plan (HCP). The HCP seeks to effectively manage the river–aquifer system to ensure the viability of the ESA-listed species in the face of drought, population growth, and other threats to the aquifer.
Although implementation of the HCP resides primarily with the EAA, a broad group of stakeholders plays a role in the management of the Edwards Aquifer.
The National Research Council (NRC) was asked to assist in this process by reviewing the activities around implementing the HCP. The NRC study was planned in three phases, with the first phase being a review of the scientific efforts that are being conducted to help build a better understanding of the river–aquifer system and its relationship to the ESA-listed species. Thus, the current report is focused specifically on a review of the hydrologic modeling, the ecological modeling, the water quality and biological monitoring, and the Applied Research Program. The fundamental question that this report addresses is whether the scientific initiatives appropriately address uncertainties and fill knowledge gaps in the river-aquifer system and the species of concern. It is hoped that the successful completion of these scientific initiatives will ultimately lead the EAA to an improved understanding of how to manage the system and protect these species.
Several topics that might be expected in this initial report are in fact going to be the subjects of subsequent reports. Thus, the current report does not evaluate the process of implementation of the HCP nor provide judgments on the policy of how the river-aquifer system should be managed. The report also does not evaluate the performance of minimization and mitigation measures currently in place, as this will be tackled in the second report. Finally, the report does not evaluate the adequacy of the goals and objectives of the HCP to protect the endangered species, as this will occur in the final report. Rather, this report evaluates whether the data are being developed that will allow a later determination of the adequacy of the goals and objectives.
The NRC constituted the Committee to Review the Edwards Aquifer Habitat Conservation Plan in early 2014—12 individuals representing expertise in all areas relevant to the Statement of Task, including the hydrogeology of the aquifer and the physics, chemistry, and biology of river systems. Four committee meetings were held during 2014. The first two meetings were held in San Antonio, Texas, and included presentations on current activities relevant to the project. We would like to thank the following individuals for giving presentations to the Committee during one or more of its meetings: Nathan Pence, Executive Director of the Habitat Conservation Program, EAA; Jim Winterlee, EAA; Mark Hamilton, EAA; Ed Oborny, BIO-WEST; Bob Hall, EAA; George Ward, University of Texas; Ron Green, Southwest Research Institute; Geary Schindel, EAA; Bill Grant, University of Texas; Todd Swannack, Engineer Research and Development Center; Thom Hardy, Texas State University; and members of the Science Committee (Doyle Mosier, Chair; Miguel Acevedo, University of North
Texas at Denton; Tom Arsuffi, Texas Tech University; Janis Bush, University of Texas at San Antonio; Jacquelyn Duke, Baylor University; Charlie Kreitler, LBG-Guyton Associates; Glenn Longley, Texas State University; Robert Mace, Texas Water Development Board; Chad Norris, Texas Parks and Wildlife Department; Jackie Poole, Texas Parks and Wildlife Department; Floyd Weckerly, Texas State University). We would also like to thank the many people who helped organize and run the field trips taken by the committee, particularly Nathan Pence, EAA; Ed Oborny, BIO-WEST; Thom Hardy, Texas State University; and Melanie Howard, City of San Marcos. These trips were invaluable to increasing the Committee’s understanding and appreciation of these unique spring systems.
Although committee members represented many diverse perspectives, we reached consensus on all recommendations included in the report. We hope that the EAA will find these recommendations useful as they guide the scientific initiatives designed to provide a solid foundation for effective management of the Edwards Aquifer and protection of the ESA-listed species.
This report has been reviewed in draft form by individuals chosen for their diverse perspectives and technical expertise, in accordance with procedures approved by the NRC’s Report Review Committee. The purpose of this independent review is to provide candid and critical comments that will assist the institution in making its published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. We wish to thank the following individuals for their review of this report: James J. Anderson, University of Washington; John D. Bredehoeft, The HydroDynamics Group; Stephen R. Carpenter, University of Wisconsin-Madison; Mary C. Freeman, USGS Patuxent Wildlife Reserve; Wendy D. Graham, University of Florida and the University of Florida Water Institute; Lora A. Harris, University of Maryland Center for Environmental Science; Rita P. Maguire, Maguire & Pearce, PLLC; Judith L. Meyer, University of Georgia (retired); Stavros S. Papadopulos, S. S. Papadopulos & Associates, Inc.; and Carol M. Wicks, Louisiana State University.
Although the reviewers listed above have provided many constructive comments and suggestions, they were not asked to endorse the conclusions or recommendations nor did they see the final draft of the report before its release. The review of this report was overseen by Patrick L. Brezonik, University of Minnesota, and R. Rhodes Trussell, Trussell Technologies, Inc. Appointed by the NRC, they were responsible for making certain that an independent examination of this report was carried out in accordance
with institutional procedures and that all review comments were carefully considered. Responsibility for the final content of this report rests entirely with the authoring Committee and the institution.
Danny D. Reible, Chair
Committee to Review the Edwards Aquifer
Habitat Conservation Plan
A Conceptual Model of the Comal Springs and San Marcos Ecosystems
Conclusions and Recommendations
Water Quality Monitoring Program
Conclusions and Recommendations
New Studies That Should Be Part of the Applied Research Program
Working Toward an Ecosystem Framework
Enhancing Review and Oversight in the Applied Research Program
Recommendations for the Applied Research Program
Data and Information Management
Performance Monitoring of Minimization/Mitigation Measures
Need for Additional Data Analysis
