Barton Springs has been called "the soul of Austin" with a history of human activity that dates back at least 10,000 years. It is the main discharge point for water that enters the Barton Spring segment of the Edwards Aquifer.
Monitoring water quality at Barton Springs is essential for assessing the cumulative impact of development on the entire Barton Springs Edwards Aquifer as well as for endangered species protection and preservation of the unique swimming site. An automatic sampler is stationed at Barton Springs to collect data on pH, temperature, turbidity, specific conductivity, dissolved oxygen, and depth. Watershed Protection groundwater monitoring staff test for suspended solids and nutrients every two weeks. Additionally, twice weekly, and following rainfall over one inch, the Parks and Recreation and/or County Health Departments test for bacteria levels.
Barton Springs is actually comprised of four separate but related spring outlets.
- Main Barton Springs, also known as Parthenia, discharges from the aquifer directly into the pool from numerous fractures and openings upstream of the diving board area. This is also where the endangered Barton Springs Salamander is primarily found.
- Eliza Spring discharges into a concrete amphitheater on the north side of the pool near the concession stand. Water is visible welling up from holes drilled into the artificial concrete floor.
- Old Mill Spring (Sunken Garden), also known as Zenobia Spring, discharges into a stone-walled pool on the south side of the creek downstream of Barton Springs pool and flows through a short tributary to Barton Creek.
- Upper Barton Springs is located upstream of Barton Springs Pool.
Groundwater tracing is a commonly used technique to understand water movement through karst aquifers like the Edwards. The dissolution of limestone occurs slowly over a long period of time and these opening are pathways or conduits for water to enter the aquifer and for groundwater to move through the aquifer. Tracing can use naturally occurring chemical in the water, introduced chemicals or dyes to track water movement. A tracer is typically introduced into the aquifer through a naturally occurring recharge feature and wells, springs and other water ways are monitored to detect the tracer.
A coordinated tracing program began in the Barton Springs Edwards Aquifer in 1996. Since that time, over 30 traces have been conducted. A special project began in 1996 in conjunction with the Barton Springs/Edwards Aquifer Conservation District (BS/EACD) called the Barton Springs Zone Dye Trace Study. Dye was injected into caves and sinkholes to map water movement in this segment. The goals were to trace the water going into the aquifer at various points in the recharge zone, measure flow rates, and determine which wells and springs the water would emerge from. Travel rates from recharge points to springs varied from 4 miles/day to 0.25 miles/day. Onion Creek is the largest contributor of the watersheds to Barton Springs under normal conditions, but a 2017 study shows that the Blanco River can be a significant source of recharge during drought conditions.
The Edwards Aquifer is an underground layer of porous limestone that stores water. While the Edwards stretches from Temple to Del Rio, the Barton Springs segment is of most interest to Austinites since the water re-emerges near the heart of downtown at Barton Springs.
Groundwater monitoring staff collect quarterly samples from six springs in the Barton Springs segment of the Edwards Aquifer: Parthenia in Barton Springs Pool, Eliza, Old Mill (Sunken Garden), Upper Barton, Backdoor and Cold.
The Barton Springs segment of the Edwards Aquifer (BSEA) is an important resource for the Austin area. It supplies drinking water to wells for numerous communities, provides habitat for endangered species, provides clean base flow to the Colorado River and supplies the City of Austin with part of its drinking water supply. Large rain events fill or "recharge" the aquifer, which feeds Barton Springs. Recharged water can begin discharging from Barton Springs in a matter of hours.
The City of Austin, the U.S. Geological Survey (USGS) and Barton Springs/Edwards Aquifer Conservation District (BS/EACD) coordinate an annual sampling program for BSEA wells and Barton Springs. Automatic data loggers are stationed to monitor impacts from rain events, discharge rates and seasonal effects.