6.2 Edwards Aquifer Authority

The EAA succeeded the Edwards Underground Water District (EUWD), which was formed after the 1951-1956 drought of record (Illgner and Schindel, 2019). The EAA was established in 1996 after lawsuits for protecting endangered species in Comal and San Marcos springs revealed the need for aquifer management. Several events set the stage for water management in Texas and the creation of the EAA, but the EAA was eventually granted regulatory responsibilities including issuing permits for wells, setting limits on groundwater pumpage, and developing a habitat conservation plan (Payne et al., 2019) to protect endangered species.

The period of 1951 to 1956 is recognized officially as the drought of record (DOR) for central Texas. For the San Antonio segment, the mean annual recharge from 1934 to 2015 was estimated at over 700,000 acre-feet (860 GL), but annual recharge for the DOR was only slightly more than 163,000 acre-feet (200 GL). Spring flows declined during the DOR. Comal Springs, which had an average discharge of 286 cubic feet per second (cfs) which is approximately 8,100 liters per second (lps), did not flow for 144 days during the summer of 1956 (EAA, 2012). The combination of no spring flow and rapidly increasing groundwater pumping led to a study to create a GCD for the San Antonio segment of the aquifer. However, the City of San Antonio insisted that rule-making authority be removed from the enabling legislation and the EUWD became the fourth GCD in Texas (there are currently over 100 GCDs), but the first without regulatory authority. This prevented the EUWD from regulating pumping from the aquifer or protecting flow at Comal and San Marcos springs. Nonetheless, the EUWD established a comprehensive groundwater data collection program, conducted research on aquifer hydrogeology, and developed a conservation plan, which included a leak-detection program.

With the passage of the Endangered Species Act (ESA) in 1973, species in both Comal and San Marcos springs have been listed as endangered. A 1991 lawsuit filed by the Sierra Club asserted that the U.S. Fish and Wildlife Service (FWS) was negligent in providing sufficient safeguards for the endangered aquatic species in Comal and San Marcos springs. In November 1992, the judge ruled in favor of the Sierra Club in response to which the Texas legislature created the EAA.

The EAA Act abolished the EUWD, addressed the EUWD regulatory deficiencies, and added other regulatory powers to the newly formed EAA. Its boundaries were also revised to reflect areas that receive water from the aquifer, not just land directly overlying the aquifer. The EAA covers all or parts of eight counties (map available) including Uvalde, Medina, Atascosa, Bexar, Comal, Guadalupe, Hays, and Caldwell counties.

Directives in the enabling legislation included:

• setting the maximum amount of pumping permits to be issued;
• setting guaranteed minimums for each permit category (municipal, industrial, and agricultural);
• only applicants with historical use during a defined historical period qualified for a permit;
• a filling deadline for permit claims was set;
• all permitted wells were required to have flow meters;
• the EAA has a lifetime responsibility for meter costs for irrigation wells;
• the EAA must have a drought plan; and,
• the EAA must have a conservation plan.

Governance of the EUWD and the EAA were markedly different. The EUWD had been governed by a 12-member elected board. The EAA’s proposed governance was a nine-person appointed board. This delayed startup as the Department of Justice did not accept replacing an elected board with an appointed board in Texas. Consequently, the Legislature followed up in 1995 with an amendment by adding a 15-member elected board from single-member districts.

To protect the endangered species, maintain spring habitats, and optimize use of the aquifer, the EAA has instituted several policies. One is establishing critical drought period triggers (based on 10-day averages) with mandated reductions in water withdrawals (Table 5) to sustain spring flows in periods of drought.

Table 5 – Triggers for critical period stages (based on 10-day averages) and withdrawal (pumping) reductions for the San Antonio segment (EAA, 2021). Index well water elevations are in feet above mean sea level (amsl) and spring flows are in cubic feet per second. 100 cfs ≈ 2.83 m³/s. Stage 5 for Comal Springs has two triggers a 10-day and a 3-day rolling average of 45 and 40 cfs, respectively.

In addition, the EAA and various municipal authorities (e.g., the San Antonio Water System) have sought additional water supplies from other aquifers, river systems and desalination; created an aquifer storage and recovery system (EAA, 2019c); and, instituted a regional water conservation program to encourage municipal water conservation and a Voluntary Irrigation Suspension Program (VISPO). VISPO authorizes financial compensation to eligible holders of irrigation rights to suspend pumping when water levels fall to a critical level defined as 193.55 m (635 feet) amsl at index well J-17 (Payne et al., 2019).