This document provides an overview of the Edwards Aquifer, which supplies water to cities like San Antonio and supports endangered species. It notes the aquifer responds directly to pumping and recharge. There are increasing demands on the aquifer from municipal, agricultural, and industrial use that have led to lawsuits to protect spring flows and endangered species. Legal challenges have established minimum spring flow rates and established the Edwards Aquifer Authority to set withdrawal limits and regulate pumping versus spring flows.

1. A Case Study of the Edwards Aquifer
Nathan Pence
Executive Director – Endangered Species Programs
Edwards Aquifer Authority

2. Edwards Aquifer

3. Edwards Aquifer
• Balcones Fault Zone
• Limestone and Artesian Aquifer
• Aquifer responds directly to pumping or recharge
• 4350 square miles
• Austin, San Marcos, New Braunfels, San Antonio
• Headwaters to San Marcos and Comal Springs

4. Edwards Aquifer cont.
• Guadalupe River baseflow
• Home to Endangered Species
• Comal Springs Dryopid Beetle
• Comal Springs Riffle Beetle
• Fountain Darter
• Peck’s Cave Amphipod
• San Marcos Salamander
• San Marcos Gambusia
• Texas Blind Salamander
• Texas Wild Rice

5. Demands on Edwards Aquifer
• Municipal Water
• Agriculture Use
• Industrial Use
• Recreational
• Biological
• Spring Flow
• Pumping vs. Springflow
Pumping vs Springflow

6. Limitations of the Edwards Aquifer
• 1956 Drought of Record– Comal Springs ceased to flow for 6 months
• Increased demand
• San Antonio: population of 2 million
• Surrounding communities
• Increased Development / Reduced Recharge
• Drought magnifies all
• Endangered Species Act of 1973

7. Legal Challenges
• Sierra Club v USFWS 1991
• Sierra Club alleged that unrestricted withdrawals from the aquifer would cause
take of Endangered Species. Courts agreed and established “take” and
“jeopardy” flow rates; water supply restrictions
• 2012 Deadline for “Continuous Minimum Springflows” for the species
• Senate Bill 1477 - 1993
• Established EAA and set withdrawal limits