Over the past several decades, TWDB staff have inventoried and entered records of nearly 140,000 water wells (including ~2,000 springs) in the TWDB Groundwater Database (GWDB). We have assigned "state well numbers" to these sites based on their location within numbered 7.5 minute quadrangles, corresponding to the U.S. Geological Survey's historical 7.5 minute topographic maps, formed by lines of latitude and longitude. The GWDB contains well information including location, depth, well type, owner, driller, construction and completion data, aquifer, water-level and water quality data. This database, thanks in part to the cooperation from private well owners and public agencies, is one of the most comprehensive statewide groundwater databases in the entire United States. We recommend reading the Database Explanation to help better understand data accuracy.
The TWDB also hosts the Texas Department of Licensing and Regulation's (TDLR) Submitted Driller's Report Database. This database contains water well reports submitted to TDLR from February 2001 to present. The Submitted Driller's Report Database assigns a tracking number as the unique identifier for each well. Older well reports are available on the Texas Commission on Environmental Quality (TCEQ) website. Only construction information on the well is available in these reports. Some wells exist in both the TWDB Groundwater Database and in the TDLR Submitted Driller's Report Database. Currently, the only way to determine if a well has both a state well number (TWDB Groundwater Database) and a tracking number (TDLR Submitted Driller's Report Database) is to view the comments/remarks for each database.
Groundwater Quality and Sampling
The purpose of the groundwater quality sampling program is to monitor changes in the quality of groundwater over time and to establish as accurately as possible the baseline quality of groundwater occurring naturally in the state's aquifers. Although groundwater used for drinking purposes typically does not contain dissolved constituents in excess of their Maximum Contaminant Levels, which could pose health risks, it is important to monitor groundwater quality periodically over time to detect trends in the concentrations of these constituents. Certain constituents pose greater risks than others as listed in the Priority Contaminant Ranking in Groundwater in Texas.
Priority Contaminant Ranking in Groundwater
Rank 1 - Severe Health Threat
- Bacteria can cause gastro-enteric illness and may indicate fecal contamination. Although it is often tested for in private wells when property with a well is sold, the analysis may not be performed at a certified lab
- Nitrate, NO3-
- The presence of NO3-/NO2- can indicate fecal contamination. Nitrate and nitrite can cause blue-baby syndrome.
- Nitrite, NO2-
- Nitrate and nitrite are immediate risks to young children and pregnant mothers.
Rank 2 - Moderate Health Threat
- Arsenic has a health-based standard based on long term risk and occurs relatively frequently in Texas public water systems (most frequently of the constituents with primary drinking water standards).
- Fluoride has a health-based standard based on long term risk and occurs relatively frequently in Texas public water supply systems (second most frequently detected in excess of primary standards).
- Gross alpha, radium 226+228
- Radionuclides (including emissions from uranium) naturally occur in several Texas aquifers. Analysis methods, identifying all three, are more expensive than for other constituents.
- Uranium may also cause metal toxicity in excess amounts, not related to emission of radionuclides. Analysis as a metal is separate from analysis for radionuclide emission.
Rank 3 - Minimal Health Threat
- Texas has naturally occurring and anthropogenic Volatile Organic Compounds (VOCs). Occurrence infrequently indicates explosion risk, with ingestion of lesser concern.
- Pesticides are rarely detected and even more rarely detected at levels above the health-based standard based on long-term (2 liters/70 years) health risks.
- Sulfate, SO4-
- Sulfate can cause "traveler's diarrhea," but does not cause any health issues to people acclimated to the water--therefore a low concern for homeowner.
- Manganese causes no identified health concerns; instead, the element causes colored water, and is therefore of less concern for the homeowner.
- Although Texas has naturally occurring and anthropogenic perchlorate, occurrence is likely not high. EPA has still not set a standard based on perchlorate (ClO4-)'s long-term risks.
- Radon is a much greater concern in air than in water, and radon detectors for air (similar to smoke detectors) are a much more efficient way of determining if a private residence is at risk from radon.
The TWDB tests for most of the dissolved inorganic constituents listed above including nutrients (nitrate/nitrite) and radionuclides. Bacteria in groundwater, while of the greatest concern for well owners using their well water for drinking, may be tested for inexpensively at many county health departments and numerous private analytical labs. Texas Agrilife Extension Service recommends that well disinfection be performed by professionals.
Primarily, the TWDB groundwater quality monitoring program consists of collecting samples directly from the aquifer, before treatment, in accordance with procedures established in the TWDB's Field Manual for Groundwater Sampling. Protocols outlined in this manual have been followed consistently since 1988 to ensure network continuity. Results from analyses sampled by other entities in cooperative agreements with the TWDB in which the TWDB's sampling protocols are followed are also entered in the TWDB Groundwater Database and coded appropriately, as are water quality data from certain other programs from a variety of state, local, and federal agencies that collect in Texas. The TWDB samples a representative number of wells from each of the state's 9 major and 21 minor aquifers, throughout their extent, once every four years.
No other state agency is equipped or mandated to monitor statewide ambient groundwater quality or obligated to sample using the TWDB's methods, although numerous other agencies collect data for their own purposes. The TWDB has recently participated in a joint research project with the Bureau of Economic Geology to provide more guidance to well owners in the state who depend on their well water for drinking purposes. As part of this Private Well Initiative project, funded by the Centers for Disease Control from 2011 through 2013, we conducted a survey of water quality data-collection programs administered by other agencies in Texas. Sampling programs are hardly a one-size-fits-all proposition and are geared toward specific customers and concerns. Whether these programs are driven by regulatory, scientific research, or determination of basic health issues, each contributes to the overall and specific knowledge necessary to characterize groundwater and its relative drinkability and usability.
Groundwater Level Measuring
The TWDB measures groundwater levels annually in nearly 2,000 wells completed in the 30 major and minor aquifers and located throughout the state. The majority of these wells are used for irrigation, household needs, and stock watering, although some are owned by small commercial water suppliers or used for industrial purposes. TWDB personnel measure depths to water in accordance with procedures outlined in the TWDB Water-Level Measuring Manual (updated September 2016). Typically they use steel tapes, sometimes electric lines and sonic detectors, or even pressure gauges if the water is under artesian pressure and rises above land surface. Annual water levels are measured during cooler months when groundwater pumping is minimal and the water levels are most indicative of static or ambient conditions.
We cooperate with nearly 50 groundwater conservation districts, federal entities such as the US Geological Survey, and numerous additional municipalities to collect water-level measurements. Currently cooperators provide at least an additional 8,000 measurements annually that are entered in the TWDB groundwater database. They measure some wells more than once a year, depending on the needs of their specific programs, and provide water-level data to the TWDB. Of all wells measured, approximately 4,000 are considered part of an "ideal" water-level monitoring network by the TWDB, based on monitoring targets of one well per 25 to one well per 125 square miles per major and minor aquifer, and depending on amount of groundwater pumpage.
Online Recorder Program
As of April 1, 2014, the TWDB maintained 184 water-level recorders, solely or in cooperation with groundwater districts, in 79 counties at wells also equipped with satellite telemetry. These automatic recorders transmit near-real-time water level data via the Geostationary Operational Environmental Satellite or GOES system. TWDB receives this information and publishes . The equipment at each site typically consists of dataloggers attached to water level recording devices, such as transducers or floats and pulleys; satellite transmitters; power sources, including solar panels; antennae; and equipment shelters.
Procedures for maintenance and troubleshooting are found in the TWDB's Field Manual for Automated Water Level Recorders. An ever increasing number of groundwater conservation districts have been able to purchase recorders and transmitters, install equipment with the help of TWDB staff, and publish data from their wells on the TWDB web site. The TWDB is currently actively seeking funding for installation of more recorders in the remaining counties in the state.