Aquifers (JPEG) are the most important water sources for drinking and irrigation for communities in the watershed. There are four major aquifers in the study area:
- Carrizo-Wilcox Aquifer
- Edwards Aquifer
- Trinity Aquifer
- Edward-Trinity Aquifer
All zones of the Edwards Aquifer are present within the Blanco-San Marcos River Watershed. Due to the unique karst geology some of the most biodiverse aquatic life is found in the springs and seeps of this basin.
Identified wells can be used as an indicator of potential growth and resulting ecological issues related to reduced groundwater or subsurface water and spring flow. Most of the existing well locations are in the central portion of the Cypress Creek Basin near the areas of Wimberley and Woodcreek, which are primarily dependent on groundwater supplies for municipal needs.
Wells are distributed throughout the Little Blanco Basin, with no discernible concentrations. The central and eastern portions of the Upper Blanco River radiate outward from the City of Blanco and support smaller developments and ranches.