Enhanced recharge to the Barton Springs segment of the Edwards Aquifer, Central Texas
The Barton Springs segment of the Edwards Aquifer is a prolific karst aquifer within Central Texas that provides groundwater for more than 60,000 people. Barton Springs is a major recreational attraction for Austin and also is habitat for endangered species. The majority of water recharging the aquifer enters along streams that flow across the recharge zone. Antioch Cave is the largest recharge feature situated in Onion Creek, one of the largest contributing ephemeral creeks for the Barton Springs segment of the aquifer. Therefore, recharge enhancement at Antioch Cave can have significant impacts on the aquifer. Modifications have been made to the entrance of Antioch Cave to increase recharge and to improve the quality of water entering the aquifer. A concrete vault with two 36-in. diameter valves was constructed over the cave entrance. One of the valves is operated by a water-quality monitoring system so that the valve will close automatically when poor quality water from storm runoff is detected. Once the initial storm pulse has passed, the valve will open to allow better quality water to enter the cave. A large screen was installed on the vault to minimize sediment and storm debris entering the cave. During periods of flow in Onion Creek, a significant groundwater mound develops in the aquifer beneath Antioch Cave. This mound increases storage in the aquifer so that during periods of drought, water levels and springflow at Barton Springs can be maintained at higher levels. Increased amounts of cleaner groundwater recharged to the aquifer via Antioch Cave provide a benefit to both the users of the aquifer and the endangered species at Barton Springs. To monitor the effects of recharge through Antioch Cave on the aquifer, a multiport well was installed at the site. This well was completed with seven monitoring zones in the Edwards units.