The Edwards Aquifer
How the aquifer works, what the recharge zone means, and why it matters for Central Texas.
Published April 10, 2026
The Edwards Aquifer is a karst limestone aquifer that stretches across 3,600 square miles of Central Texas. It is one of the most prolific aquifers in the world and the primary drinking water source for San Antonio, San Marcos, New Braunfels, and surrounding communities.
How it works
Water enters the aquifer through the recharge zone — a band of exposed, fractured limestone where rainwater percolates directly into the rock. The recharge zone runs roughly from Brackettville to Austin, passing through Hays County. Once underground, water flows through interconnected solution caves and fractures under artesian pressure, eventually discharging at springs.
The most famous discharge points are:
- Comal Springs (New Braunfels) — the largest springs in Texas
- San Marcos Springs (San Marcos) — home to the San Marcos River and multiple endangered species
The J-17 index well
Drought stages are triggered by water levels at the J-17 index well in Bexar County (San Antonio). When the well drops below designated thresholds, the Edwards Aquifer Authority mandates reduced pumping across all user categories. Stage 3 — the current status in Hays County — represents severe drought with mandatory restrictions.
Current drought conditions
As of early 2026, conditions in Hays County are at historic lows. 100% of monitored wells in the Hays Trinity Groundwater Conservation District have fallen below their historic records — worse than the 2011 drought, the worst in the district's 20+ year history.[1] The Barton Springs-Edwards Aquifer Conservation District entered Stage 3 Exceptional Drought in October 2025 and came within 0.7 feet of the Stage 4 Emergency Response threshold in March 2026.[2]
Sources
- ^ KUT News, "Hays County wells run drier than ever recorded as aquifer levels drop," March 2026. Available at kut.org.
- ^ Barton Springs-Edwards Aquifer Conservation District, "Drought Update: February 2026," March 2026. Available at bseacd.org.
Aquifer Water Budget
Where recharge goes — pumping by category, spring discharge, and where proposed data centers fit in the overall picture.
Long-term annual average (1934–2013). Recharge outpaces pumping; the aquifer maintains a modest storage buffer.
Full data for the Edwards Aquifer water budget, Average Year:
Interactive diagram available on wider screens. Full data shown in table below.
| Category | MGD | % of Total |
|---|---|---|
| Precipitation Recharge1 | 624 | — |
| Municipal Pumping1 | 209 | 33.5% |
| Spring Discharge1,2 | 208 | 33.3% |
| Net Storage (buffer)1 | 104 | 16.7% |
| Agricultural Irrigation1 | 68 | 10.9% |
| Industrial Use1 | 23 | 3.7% |
| Domestic & Livestock1 | 12 | 1.9% |
| Proposed Data Centers ✱3,4 | 3–15 MGD | 0.5–2.4% |
✱ Hypothetical range for 3 proposed Hays County data centers. Not currently drawing from the aquifer.