Update on Central Hays County Groundwater Evaluation near EP Test Wells

From the Barton Springs/Edwards Aquifer Conservation District:

In response to recent Electro Purification test wells, their proposed groundwater withdrawals, concerns from surrounding well owners, and legislative debate, the BSEACD has been collaborating with area groundwater districts to evaluate groundwater systems in Central Hays County.  Please visit the Trinity Well Drilling page for more details, maps, and presentations.


We have been processing the data from the Central Hays County March 2015 Water Level Snapshot and wanted to provide a summary of the data gathered, an update on the status of the ongoing groundwater evaluation, and an overview of upcoming monitoring efforts.


Water Level Data

First, thanks to all the well owners that have allowed access to your well.  Staff from the Edwards Aquifer Authority, Hays Trinity Groundwater Conservation District, and the Barton Springs/Edwards Aquifer Conservation District were able to visit 65 wells in Central Hays County from March 17 – 20, 2015.  Overall since January 2015, 156 water level measurements have been taken at 81 wells.


Staff uses two instruments to measure water levels: an eline and/or a sonic meter.  Eline measurements are the most reliable and accurate.  Eline measurements can be made by accessing the well through the observation port then lowering measuring tape with a sensor on the end 100-350′ down to the water level, which has its challenges.  Sonic meters are much easier and faster, but depending on the well completion, they may not be as accurate.  Sonic meters use a sound pulse that bounces off the water surface and back to the instrument to calculate the distance to the water surface.  Obstructions or irregularities in the well can affect the readings, so it is good to get both eline and sonic readings to check the validity of the sonic measurements.


Well owners received a record of all the water level measurement(s) taken at their well (Jan-Apr 2015).  The instrument used for the measurement is documented on the Water Level Report.  Additionally, staff attempted to estimate the general aquifer for each well.  See the included figure titled “Generalized Stratigraphy of the Edwards and Trinity Aquifers” on the Trinity Well Drilling page for additional info.


Groundwater Evaluation Status

Water level and basic field parameter measurements gathered as part of the snapshot are critical elements in the evaluation of the local hydrogeology (aquifers, confining units, and flow paths).  This evaluation is a good first step to understanding the groundwater systems at play in Central Hays County–where the Edwards (where present) and Trinity Aquifers are known to be exceptionally complex and variable.  A preliminary groundwater evaluation, summarized by the Barton Springs/Edwards Aquifer Conservation District hydrogeologists and reviewed by the collaborating groundwater conservation districts’ staff, is underway and should be available in about a month.


Monitoring Efforts

To date, the water level monitoring has been funded and conducted solely by the collaborating groundwater districts.  Based on the initial round of well visits, water level measurements, and well completion information wells have been assigned to monitoring categories: transducer sites, frequent measurements, periodic measurements, and willing to be monitored.  Amap of monitoring sites is also available on the Trinity Well Drilling page.


Transducer Sites:

A small number of wells that have good well records (geophysical logs, driller’s records, etc.) will be equipped with a drop pipe and a pressure transducer that is programmed to record a measurement at defined intervals.  Transducers measure the pressure of the water column above the instrument, which can be easily converted into a water level measurement.  Retrofitting wells with the drop pipe and purchasing and maintaining the transducers is costly, so wells are being thoroughly researched and selected to best represent key aquifer formations at various distances and directions from pumping centers.  The first round transducer sites are located just north of the Electro Purification test wells and are expected to be operating soon.  Additional transducer sites will be established to the south then at greater distances (in the 1-2 mile buffer zones).  It is estimated that there will be 10-12 transducer sites in total.  It was suggested to Electro Purification, that rather than plug Bridges #3, they convert it into a monitor well.  Cost would be roughly equivalent to the plugging, and this is in line with their statements saying they support a monitor network.


Frequent Water Level Sites:

A larger number of wells are planned to be measured frequently.  These wells generally have good well completion records and reflect water levels associated with discrete aquifer interval–typically Upper Trinity, Middle Trinity, or Middle Trinity (Cow Creek). Staff from the collaborating groundwater conservation districts plan to visit these wells about every 2 months to document seasonal water level fluctuations and more frequently if/when a pump test is in progress.


Periodic Water Level Sites:

A large number of wells are considered periodic water level sites.  These sites have or will have a baseline water level measurement.  Pump configuration or hybrid aquifer well completion often make measurements at these sites difficult or not representative of a discrete aquifer interval.  Water level data at these sites are good to track for seasonal trends but not optimal for evaluating groundwater system dynamics.


Willing Monitor Sites:

These sites have not been measured, but well owners have offered well information to be included in the groundwater evaluation.  Contact info is on hand for when there is a gap or alternate site needed.


The data collected as part of the collaborative groundwater evaluation will be critical in better understanding aquifer dynamics, drought response, and influence of pumping on nearby wells.  This data can be used to inform future policy and management decisions.


Discussion of the proposed production wells has been widespread–through social media, on neighborhood list serves, in meetings, in the press and at the legislature.  On behalf of the collaborating groundwater conservation districts, thank you for your support and interest in the groundwater evaluation in Central Hays County.


Robin Havens Gary

Senior Public Information and Education Coordinator

Barton Springs/Edwards Aquifer Conservation District

1124 Regal Row

Austin, TX 78748

512-282-8441 phone

512-282-7016 fax