PROJECT LINKS

• South-Central Texas (SCTX) National Water-Quality Assessment (NAWQA)
  • SCTX Home Page
  • Summary of major findings
  • Publications
  • Summary of data collection, 1996–2004
  • Liaison Committee
  • NAWQA - Data
  • NAWQA home page

EDWARDS AQUIFER

• Current Studies
  • Barton Springs Groundwater Characterization Project
  • Stormwater Runoff
  • Hydrogeology of the Edwards aquifer
  • Evaluation of Seco Creek Basin
  • South-Central Texas (Edwards) NAWQA
  • Hydrogeology of Medina Lake, Medina-Bandera Counties

• Publications
  • Water-Related USGS Reports
  • Comprehensive Bibliography

• Other Resources
  • Levels from San Antonio Water System (SAWS)
  • Level from Edwards Aquifer Authority (EAA)
  • Geologic Discipline Edwards Project Web Site
  • Recharge Summary

USGS IN YOUR STATE

USGS Water Science Centers are located in each state.

Program of the USGS in Texas
South-Central Texas (Edwards) National Water Quality Assessment (NAWQA)

PROBLEM

The Edwards Aquifer in the San Antonio area is the major water resource in south-central Texas. This highly productive carbonate aquifer, designated as a sole-source aquifer by the EPA in 1975, is the principal water supply for more than 1.5 million people. The sole-source designation serves as official recognition that contamination of the aquifer would create a significant hazard to public health. The unconfined, highly permeable recharge zone of the aquifer is very susceptible to contamination from human activities associated with rapidly increasing population growth and urban development there. Streams and the Trinity aquifer in the "catchment area" north and west of the recharge zone, a largely undeveloped area where the water that enters the aquifer in the recharge zone originates, also are susceptible to contamination associated with encroaching development. In addition, the needs for water supply from the Edwards aquifer are in direct competition with the habitat needs for five federally listed endangered or threatened species associated with Comal and San Marcos Springs, the principal natural discharge features of the Edwards Aquifer.

OBJECTIVE

To describe the status and (where possible) trends in the chemical and biological constituents of streams and the Edwards and Trinity aquifers in the upper part of the study unit (the upper parts of the Nueces, San Antonio, and Guadalupe River Basins); and to provide a sound scientific understanding of the primary natural and human factors (particularly land use) affecting those constituents. [Note: The study unit comprises the entire Nueces, San Antonio, and Guadalupe River Basins; however, the initial High Intensity Phase of the study (1994-2000) focuses only on the upper parts of those basins.]

APPROACH

Gather and analyze the existing information on the chemical and biological constituents of streams and the Edwards and Trinity aquifers. Sample and analyze the surface water, streambed sediment, and tissues associated with different land uses, and ground water in the Edwards and Trinity aquifers. The surface-water, sediment, and biological sampling will be done during different seasons and under different flow conditions to better understand seasonal and flow effects on stream quality. Synoptic ground-water sampling will be done in the Edwards and Trinity aquifers to assess overall quality, and in the recharge zone of the Edwards aquifer, to assess the relation between ground-water quality and urbanization.

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