The Barton Springs watershed, also referred to as the Barton Springs segment or zone of the Edwards Aquifer, spans roughly 240,000 acres of contributing and recharge areas in southwestern Travis and northern Hays counties. The contributing zone (light green), the larger area, includes creeks and rivers that eventually drain and flow across exposed surface areas, where water seeps through the highly porous rock, sinkholes, and caves that make up the recharge zone of the aquifer (darker green). Any pollution that ends up in the contributing zone's waterways may eventually find its way to the recharge zone, where it can enter the aquifer and contaminate the springs.
The Barton Springs segment of the aquifer has been identified by the state as the most endangered aquifer in Texas. Its vulnerability is largely attributed to its small size, its high porosity and the area's population boom, bringing with it massive developments and roadway construction.