The Trinity aquifer is an important source of groundwater in central Texas, including Bexar County, where population growth has resulted in an increased demand for water. Numerous springs issue from rock outcrops within and surrounding the Trinity aquifer in northern Bexar County. The effects of increased groundwater withdrawals from the Trinity aquifer on springflow in the area are not well documented, but because the total amount of water entering, leaving, and being stored in a groundwater system must be conserved, increased groundwater withdrawals will result in decreases in springflow. Documenting the location, discharge, and basic water-quality information of the springs in northern Bexar County can provide a baseline assessment for comparison to future conditions. Accordingly, the U.S. Geological Survey, in cooperation with the Trinity Glen Rose Groundwater Conservation District, the Edwards Aquifer Authority, and the San Antonio River Authority, developed a geodatabase populated with data associated with springs within and surrounding outcrops of the Trinity aquifer in northern Bexar County during 2010–11. A geodatabase provides a framework for organizing spatial and tabular data (such as the geographic location and water-quality characteristics, respectively) in a relational database environment, making it easier and more intuitive to evaluate changes over time.
Data for 141 springs within and surrounding the Trinity aquifer outcrops in northern Bexar County were compiled from existing reports and databases. A field reconnaissance of springs was done between October 2010 and September 2011 to verify the existing location data and collect additional data (discharge measurements, water-quality data, and property owner and photographic documentation) pertaining to the springs. A total of 46 of the 141 springs were visited during the field reconnaissance. Discharge at springs with flow ranged from 0.003 to 1.46 cubic feet per second. Specific conductance was measured in 21 springs and ranged from 167 to 1,130 microsiemens per centimeter at 25 degrees Celsius.
Increasing water demands are likely to continue to affect springflows throughout Texas. By completing reconnaissance-level field investigations and compiling existing data, similar geodatabases could be developed for other aquifer systems in Texas.
Additional Publication Details
USGS Numbered Series
Development of a geodatabase for springs within and surrounding outcrops of the Trinity aquifer in northern Bexar County, Texas, 2010-11