Aquifer Information

(Note: This link is continually updated, please check back)

Final version of the report on the Middle Trinity Potentiometric Map or visit the following website:


The District offers limited water quality testing for Blanco County well owners. District staff will need access to your well for less than an hour. During that time we will try to measure the water level in the well, conduct some on-site measurements, take a bacteria sample in a sterile bottle, and take a water chemistry sample that will be analyzed in the District laboratory for the more common chemical constituents. The District does not charge for this service. To schedule a water quality test, call District Hydrogeological Technician, John Dabney, at (830) 868-9196 or email him at:

Tips and Information Regarding Your Well


1.) A Guide to Understanding your Water Quality Report

The Blanco Pedernales Groundwater Conservation District appreciates your participation in the water quality sampling program. As part of our commitment to well owners, we have prepared this guide to help you examine and understand the results of the water quality analysis of your well water. Water quality standards are divided into two groups, Primary and Secondary. Primary standards apply to constituents that have maximum contaminant levels (MCL) designated to protect human health. Secondary standards are recommended maximum contaminant levels which are generally associated with taste, odor, appearance, staining, and other annoyance-type problems. Below is an explanation of each constituent tested and its maximum contaminant level when applicable.
Guide to Understanding your Water Quality Report.pdf


2.) A Do-It-Yourself Guide to Chlorinating Your Water Well

The Blanco-Pedernales Groundwater Conservation District receives frequent requests for information on how to chlorinate water wells. In an attempt to answer this question in a clear and easily understood manner, the District is providing this guide as a courtesy and convenience to well owners. Whether or not you chlorinate your well and how you go about are decisions you must make. The following chlorination treatment guidelines are those generally used by many well owners and professional well service companies. In most cases, these procedures will successfully sterilize your well of bacteria. The procedures are relatively simple, but can be hazardous. If you have any doubts about your ability to safely and properly follow these procedures, you are urged to contact a well service company for professional help. The District is not responsible for any injuries, problems, damages, or bacterial reoccurrences resulting from the use or misuse of this information.
Chlorinating a Well.pdf


3.) Sulfate in Blanco County Groundwater

Sulfate (SO4) occurs naturally in most of Blanco County groundwater, with higher levels often common in the Upper Glen Rose and Middle Trinity Aquifers found in the southern half of the county. At high levels, sulfate can give water a bitter or astringent taste and can have mild laxative effects. Sulfate in drinking water currently has a secondary maximum contaminant level (SMCL) of 250 milligrams per liter (mg/L), based on aesthetic effects (i.e., taste and odor). This regulation is provided by the Environmental Protection Agency. It is not a Federally enforceable standard, but is provided as a guideline for States and public water systems.
Sulfate Info.pdf



A Texas Manual for Rainwater Harvesting

Rainwater harvesting is an ancient technique enjoying a revival in popularity due to the inherent quality of rainwater and interest in reducing consumption of treated water.
Rainwater Harvesting Manual 3rd Edition.pdf