Hydrogeologic and Geochemical Investigation of the Trinity and Northern Segment Edwards Aquifers

Science Center Objects

The USGS Texas Water Science Center, in cooperation with the Clearwater Underground Water Conservation District and Bell County Adaptive Management Coalition, is evaluating the hydrogeology and water quality of the Northern segment of the Edwards and Trinity aquifers in Bell County to provide regional resource managers responsible for regulation of water use and drought management strategies with a more comprehensive understanding of these aquifers.

This evaluation of water resources in Bell County will be multi-phased and will include an evaluation of the relation between the Edwards aquifer and other regional water resources including surface water and the Edwards-Trinity aquifer in the vicinity.  The assessment of the Northern segment will include the evaluation of existing hydrologic and geochemical data available from previous studies and collection of new information from real-time data loggers and discrete sample collection.  This approach would provide information on nutrients and contaminants in recharging surface water, groundwater, and spring discharge, as well as providing a baseline of understanding for assessing future impacts on the aquifer.  The study design will be a phased approach, with subsequent phases building on hydrologic and geochemical knowledge gained in previous phases. 

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Salado Creek at Salado, TX (crop)

USGS and Bell County Cooperative Science

Access USGS data for Bell County and learn more about the history of USGS data collection activities in the area.

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PHASE ONE (2012)

Collecting water-quality samples from unconfined Edwards aquifer well FM2843

Collecting water-quality samples from unconfined Edwards aquifer well FM2843 during Phase One of the project. (Public domain.)

  • Six spring orifices in the Salado Springs complex were sampled in conjunction with two wells, one in each of the confined and unconfined portions of the Edwards aquifer.  
  • Salado Creek downstream from confluence of N. and S. Salado Creeks was sampled.
  • Upper Trinity well at Micheaux Ranch was sampled.

PHASE TWO (2013)

  • A streamflow gage was installed on Salado Creek as a low-flow streamflow gage.
  • Paired samples were collected at Big Boiling Spring and Stagecoach Inn “cave” well under baseline conditions.
  • Paired samples were collected at Big Boiling Spring and Stagecoach Inn “cave” well following light rain.
  • Big Boiling Spring was sampled following moderate rain.

PHASE THREE (2014)

Salado Creek sampling

Monica Langhorst, USGS, collecting a sample from Salado Creek  during Phase One of the project. (Public domain.)

Collecting water-quality samples from a well inside a cave near Stagecoach Inn, Texas

Collecting water-quality samples from a well inside a cave near Stagecoach Inn, Texas. (Public domain.)

  • Low-flow streamgage was expanded to full range capabilities.
  • Paired samples were collected under varying hydrologic conditions at Big Boiling Spring, which has the highest springflow of the six springs, and an underground “cave” well located nearby.
  • Paired samples were collected at Big Boiling Spring and Stagecoach Inn “cave” well following heavy rain along with grab sample from Salado Creek for major ions, nutrients, and trace elements (Strontium and Boron only).
  • Paired samples were collected at Big Boiling Spring and Stagecoach Inn “cave” well following light precipitation event twice.

PHASE FOUR (2015)

  • Full range streamflow gage maintenance.
  • Multiple samples were collected at Big Boiling during a multi-day precipitation event.
  • Paired samples were collected at Robertson Spring and Robertson well.
  • Sample was collected from Big Boiling Spring following light precipitation event.
  • Weekly monitoring of geochemical properties at 4 Northern Edwards springs took place from mid-May to late-July.

PHASE FIVE (2016)

  • Full range streamflow gage maintenance.
  • The same six spring orifices sampled in 2012 were resampled at a higher base-flow level.
  • Discharge and water quality were compared.

PHASE SIX (2017)

  • Full range streamflow gage maintenance.
  • Collected a variety of geophysical logs/data as part of a toolbox approach at approximately 6 selected wells completed in some combination of the Upper, Middle, and Lower Trinity aquifers and the Edwards aquifer to gain a better understanding of the subsurface hydrogeology and well construction in those locations. Types of logs included:
    • Caliper
    • Casing collar locator
    • Natural gamma
    • Fluid resistivity/temperature
    • Single point resistivity
    • Induction conductivity (if well is PVC-cased)
    • Long and Short Normal resistivity (if well is uncased)
  • Water-quality data collected since 2012 will be published as a USGS Data Release.
  • Synoptic water-quality samples from wells in southern Bell County were analyzed to look at potential sources of nitrate to the Edwards aquifer in Bell County.

PHASE SEVEN (2018)

  • Will collect a variety of geophysical logs/data as part of a toolbox approach at a well completed in the Middle Trinity aquifer in Holland City to gain a better understanding of the subsurface hydrogeology and well construction at that location.
  • Will analyze 20 archived samples that were collected by Baylor University staff in 2014 for nitrate isotopes.
  • Compile all water quality data collected by the USGS, either in conjunction with this project or historically in Bell County, in a USGS ScienceBase data release.
Comparison of Little Boiling Spring sampling site from 2012 and in 2015

Comparison of Little Boiling Spring sampling site from 2012 (left) and in 2015 (right).   (Public domain.)