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  • What is the Relationship Between Water Levels in Wells and Groundwater Quality and Quantity?
    There are many variables that influence groundwater quality. Aquifer rock type, soluble minerals present and their concentration, groundwater flow paths through the aquifer, contact or residence time, and recharge rates are examples of variables that influence groundwater quality. Other factors such as well depth, use, and well construction can also control water quality in a well. In general, groundwater quality with respect to water level changes is small. However, in certain situations water levels can lead to changes in water quality. For example, saltwater encroachment may occur in coastal aquifers where pumping reverses the hydraulic gradients resulting in increasing dissolved mineral concentrations. This has occurred in a number of coastal wells resulting in increasing salinity above drinking standards which is detrimental to groundwater quality. Water level changes in wells are driven by the interplay between groundwater recharge and discharge to and from aquifers. In general, water levels in wells decline due to increased groundwater withdrawal and/or reduced aquifer recharge. Conversely, limited groundwater discharge, a decrease in groundwater discharge, and/or increased aquifer recharge causes water levels in wells to rise. There are two situations to consider. Unconfined (water-table) aquifers In water-table aquifers, water levels in wells are direct indicators of the amount of groundwater stored in an aquifer at a given time. Well water levels are constantly changing both in the short term and over the long term. Water levels fluctuate in response to changes in the quantity of water stored in that particular area of the aquifer. When the quantity of groundwater in an aquifer increases, water levels in wells rise. When the quantity of groundwater in an aquifer decreases, water levels in wells decline. Confined aquifers Changes in water levels in confined aquifers are not necessarily correlated to changes in aquifer storage. This is because confined aquifers respond to pumping in a different way from unconfined aquifers. In unconfined aquifers, dewatering of the formerly saturated space between grains or in cracks results in significant volumes of water being released. On the other hand, pumping in confined aquifers causes a decrease in water pressure – as opposed to a drop in water volume – in the aquifer near the pumping well. Within a confined aquifer, as pressure is reduced, the aquifer material compresses, porosity decreases, and the amount of water stored declines. The water levels in wells will drop somewhat but the entire thickness of the aquifer will remain saturated during pumping. For additional information on changes in your water well level, contact your local Groundwater Conservation District (GCD) representative at For additional Frequently Asked Questions (FAQs) related to groundwater quantity, groundwater quality, septic systems, water wells, administrative entities, and publications, visit the Texas Groundwater Protection Committee’s FAQ webpage at .
  • Why Monitor Groundwater Levels?
    For Texas, groundwater is a vast resource, the importance of which cannot be overstated. There are thirty major and minor aquifers in the state that range from shallow, unconsolidated sand and gravel deposits underlying river valleys to deep rock aquifers that cover large parts of the state. Of the 16.1 million acre-feet of water used in Texas in 2008, groundwater contributed 9.7 million acre-feet, or about 60 percent, with surface water supplying the rest. Because of the importance of Texas’ groundwater supplies, the Texas Water Development Board (TWDB) and local Groundwater Conservation Districts (GCDs) monitor water levels statewide to detect changes. Water level information is important for managing groundwater resources, developing groundwater availability models, and planning to meet future demands for water. The TWDB and their cooperators maintain a statewide water level monitoring network consisting of approximately 8,000 wells. Once a year, field technicians measure the depth to water in most of these wells. Monitoring groundwater levels in wells serve much the same purpose as periodically checking the oil-level dipstick on an automobile engine. If the engine developed a problem and started using oil, the dipstick oil mark would alert the driver before expensive repairs are needed. Similarly, the monitoring well network helps serve as an early warning system that can identify where groundwater use is occurring at a rate that the aquifers of Texas cannot sustain indefinitely. For additional information on monitoring groundwater, see Texas Water Development Board (TWDB) at: Texas Alliance of Groundwater Districts (TAGD) at:, and United States Geological Survey (USGS) at: For additional Frequently Asked Questions (FAQs) related to groundwater quantity, groundwater quality, septic systems, water wells, administrative entities, and publications, visit the Texas Groundwater Protection Committee’s FAQ webpage at
  • Water in Texas – Who Owns It?
    Since water is one of our state’s most valuable natural resources, it continues to be a highly political and sensitive issue. However, there are many misconceptions and differences that are unique to water ownership compared to many of our state’s other natural resources. Because supplies are limited in many areas of the state, competition for water is rising among groups and individuals in Texas. In order to protect both the individual’s own interests as well as those of the state, Texas residents need to be informed on exactly what their water ownership rights entail. Water comes from either groundwater or surface water. Surface water is found in ponds, lakes, rivers, streams, and bays. Groundwater filters down from the earth’s surface and accumulates underground in aquifers. On average, about 80 percent of all groundwater used in Texas is utilized for irrigating crops. Conversely, the majority of surface water is confined to use within cities and industry. In Texas, water rights depend on whether the water is surface water or groundwater. Surface water is publicly owned and governed by the State of Texas. Without a permit from the Texas Commission on Environmental Quality (TCEQ), landowners may only use surface water for domestic and livestock purposes. If a landowner wishes to use the surface water for other sources such as irrigation, manufacturing, or power generation, he or she must obtain consent from the state in the form of a permit. Some landowners may have concerns about whether the state requires them to obtain a permit to build a reservoir on their property for the use of a stock tank. This falls into the “stock tank exception” that allows landowners to build up to a 200-acre-foot reservoir on their property without receiving permission from the state. An acre-foot is the amount of water that will cover an acre of land one foot deep (over 325,850 gallons). Some concerns arise on the ownership of diffused surface water, which is surface water, in its natural state, that occurs after a rainfall or snowmelt, and runs off a roof or flows across the land in an unpatterned way. Diffused surface water is commonly referred to as storm water, drainage water, or surface runoff. Texas law states that diffused surface water is the property of the landowner until it enters a natural watercourse. Once this water enters a natural watercourse it becomes property of the state. The “stock tank exception” as discussed above does not apply to diffused surface water. This means that a landowner may harvest the rainwater into the soil, or capture and store drainage water, as long as the water is captured before it reaches a natural water course. Unlike surface water, groundwater is the property of the landowner, which allows a landowner the right to capture the water beneath his or her property, and sell, lease, and move the water pumped from his or her property to a neighbor, corporation, or city. Historically, groundwater has been governed by “the rule of capture,” or the law of the biggest pump, which allows a person, with legal right to the groundwater, the right to pump whatever groundwater is available, regardless of the effects that pumping may have on neighboring water wells. Texas courts have limited the rule of capture in order to prohibit a landowner from: Pumping water for the purpose of maliciously harming an adjoining neighbor; Pumping water for a wasteful purpose; Causing land subsidence (sinking) on adjoining land from negligent pumping; and, Drilling a slant well that crosses the adjoining property line. State of Texas legislators have passed several laws that curtail groundwater pumping. Three major restrictions which have been imposed to prevent unlimited pumping of groundwater can be found in the Texas Water Code. These restrictions govern: Pumping water that comes from the underflow of a river; Pumping groundwater from an aquifer within the jurisdiction of a Groundwater Conservation District (GCD); and, Pumping groundwater from the Edwards Aquifer within the jurisdiction of the Edwards Aquifer Authority. GCDs are the state’s preferred method of groundwater management through rules developed, adopted, and promulgated by a district in accordance with the provisions of the Texas Water Code and their enabling legislation. Texas law authorizes GCDs to modify the rule of capture by regulating groundwater production through permitting of non-exempt water wells, well spacing requirements, and through other rules as deemed necessary to conserve, preserve, protect, recharge, prevent waste of groundwater, and to control subsidence. Additional information concerning landowners’ water rights may be obtained from the Texas Commission on Environmental Quality at, the Texas A&M AgriLife Extension Service at the Texas Water Code at, or the Texas Alliance of Groundwater Districts at For additional Frequently Asked Questions (FAQs) related to groundwater quantity, groundwater quality, septic systems, water wells, administrative entities, and publications, visit the Texas Groundwater Protection Committee’s FAQ webpage at
  • What Are the Texas Evapotranspiration (ET) Networks?
    What is evapotranspiration and why is it important to groundwater users? Evapotranspiration (ET) measures the amount of water needed to grow plants and crops. Different plants have different water requirements. This means they have different ET rates. When water users like farmers and homeowners use evapotranspiration data to understand the true water requirements of their plants, they may be able to reduce their water use. This information is useful for homeowners and businesses that water landscapes and can be especially impactful for farmers that use groundwater to irrigate their crops. What is reference evapotranspiration (ETO)? The term reference evapotranspiration (ETO) is the water requirements of a cool season grass growing four inches tall under well-watered conditions. ETO is used along with crop coefficients and plant factors to determine the actual water requirements (or ET) of crops and plants. ETO depends on the climate and varies from location to location. The climatic data used in calculating ET includes: temperature, dew point temperature (relative humidity), wind speed solar radiation What is an ET Network? An ET Network is a collection of weather stations that use special sensors and methodologies to calculate ET and provide watering recommendations to end users. While there are many existing weather station networks, not all meet the criteria for ETO data collection. For example, the National Weather Service stations do not have solar radiation sensors and cannot be used to directly determine ET. Another factor that is important for data collection is the location of the stations. ET stations are sited in large open grassy areas, receive full sun, and the wind is not blocked by trees or buildings. How does an ET Network operate? Special weather stations (see Figure 1) measure the parameters needed for the calculation of reference evapotranspiration (ETO). The network calculates ETO which is used to determine plant water requirements and irrigation needs. The network disseminates plant water requirements and irrigation needs to end users through online access, online tools, emails, push notifications, and other methods. Figure 1: ET Weather Station What is the TexasET Network? The TexasET Network is the only network in Texas that meets all the ET Network criteria listed above. This network began in 1994 and consists of 88 weather stations statewide. Currently, TexasET is incorporating data from 26 stations of the Texas Water Development Board’s (TWDB) TexMesonet that meet ET station sensor and siting requirements. Additional TexMesonet stations are being evaluated for future incorporation into TexasET. Funding for the TexasET Network comes from short courses, contracts, grants, and fees. Much of the funding for the weather stations depend on local sponsors. Sustainable funding is necessary to continue TexasET Network. The TexasET Network website displays daily weather and ETO data, heat units, and other data. It also offers interactive, easy-to-use calculators that allow users to determine the irrigation water requirements of crops and landscapes. Users can download data directly from the website or set up automatic email notifications of customized weather data and irrigation recommendations. What is WaterMyYard and how does it relate to the TexasET Network? The WaterMyYard (WMY) program uses stations in the TexasET Network to calculate ET data and delivers watering recommendations to residents of 11 participating cities, water districts, and public utilities. The program focuses on home landscapes of warm season grasses such as St. Augustine, Bermuda, Zoysia, and Buffalo. Users can receive weekly texts, emails, and push notifications with recommendations for irrigation system runtimes, along with any applicable information on local watering restrictions. The Irrigation Technology Program of the Texas A&M AgriLife Extension Service partnered with the North Texas Water Municipal Water District and piloted WMY in 2013. This program received the Blue Legacy Award for responsible management of water resources in 2015 and released Android and iOS apps in 2020. With little understanding of ET, residents in sponsored areas can set up a personal profile and configure their yard and notification preferences. Users are encouraged to use “catch can” tests to determine precipitation rates, or they can select their precipitation rate based on their equipment and spacing. With continued support and growing interest from new partners of the WaterMyYard program, the TexasET Network has added 44 stations to its ET network to provide accurate data for the urban areas participating in WaterMyYard. Are there any discontinued ET Networks in Texas? At one time, Texas had five ET networks operating in different regions of the State. Due to funding issues only one ET Network remains. Discontinued networks were programs of Texas A&M AgriLife Research. In 1994, the North High Plains Potential Evapotranspiration (PET) Network launched. The South High Plains PET Network launched a few years later. These two networks were merged to form the Texas High Plains PET Network. This network ceased operation in 2013. In 2000, the Crop Weather Program for South Texas launched. This program focused on the Coastal Bend region and aimed to provide data for use by cotton farmers. This network ceased operation in 2017. There are also two smaller regional ET networks that are no longer are in operation. These are the Precision Irrigators Network from Uvalde and the South Texas Weather Network from Weslaco. Are there any other related weather station networks? There are two ET related weather station networks in Texas. While these do not meet the definition of an ET Network, some of their stations contain all the required sensors and are sited properly for determination of ETo. The West Texas Mesonet (WTM) project provides free real-time data for residents of the South Plains region of western Texas. Established in 1999, the network covers 54 counties in Texas and New Mexico with 77 surface meteorological weather stations. The WTM posts daily ETO values. However, it is not considered an ET network because it does not have a notification program or tools for determining irrigation requirements and not all stations are in sited properly for ET determination. In 2016 the Texas Water Development Board launched the TexMesonet. TexMesonet is unique because it consists of its own weather stations and serves as a “network of networks.” This means that TexMesonet includes its own data as well as data from other stations and networks. There are currently 85 TWDB-maintained rural area stations in the Network. Many of these stations measure all of the parameters needed for calculation of ETO and are sited properly for ET determination. The TexMesonet does not offer a notification program or tools for determining irrigation requirements for end users. Where can I get more information? For maps, publications, and additional information, go to: TexasET Network,; WaterMyYard,; West Texas Mesonet Project, TexMesonet, For additional Frequently Asked Questions (FAQs) related to groundwater quantity, groundwater quality, septic systems, water wells, administrative entities, and publications, visit the Texas Groundwater Protection Committee’s FAQ webpage at
  • Brush Control/Management (TWDB/TSSWCB)
  • Pesticides in Urban Groundwater
    Texas Groundwater Protection Committee FAQs January 2024 Pesticides in Urban Groundwater During monitoring and investigation activities, Texas Commission on Environmental Quality’s (TCEQ) Public Drinking Water Section and the United States Geological Survey (USGS) discovered common situations that could lead to pesticides entering groundwater, including: ·Improperly using pesticides such as not following Labeling instructions. Mixing or loading pesticides in facilities located near water wells. Applying pesticides near abandoned, improperly plugged, or corroding water wells. Using pesticides near seasonal surface water features such as playa lakes and intermittent creeks. Using an especially high amount of pesticides. History This timeline details past and current pesticide monitoring activities. 1990s TCEQ began to use a screening procedure called an immunoassay to measure pesticide residues. This method detects certain pesticides at very low concentrations. Using this new method, TCEQ began to screen groundwater samples collected from rural areas across the state. This was the first statewide screening program for atrazine, a popular herbicide. 2000 Laboratory method for atrazine decreased the detectable amount from 1 to 0.1 parts per billion (ppb). The statewide aquifer screening program added another herbicide, metolachlor. TCEQ began coordinating groundwater monitoring with the Texas Water Development Board and individual groundwater conservation districts. TCEQ collected and analyzed groundwater samples for atrazine and metolachlor over a seven-year period. Detections of both pesticides were very low with concentrations of less than 0.05 ppb, or about 0.05 ounces in 31,000 tons. TCEQ identified a clustering of low atrazine detections located in five Public Water Systems (PWSs) in the central Panhandle. Most of the atrazine concentrations were below the drinking water Maximum Contaminant Level (MCL) of 3 ppb. A few water wells triggered Texas State Pesticide Management Plan activities. Texas A&M AgriLife Extension worked with crop producers and water well owners to provide education and outreach in the Panhandle region of the state. TCEQ used the data to focus educational and outreach efforts. 2,4-D replaced metolachlor. 2007 TCEQ began sampling groundwater in urban areas. San Antonio and Austin were part of this sampling effort. Testing began for the five pesticides or pesticide families using the immunoassay screening method. Pesticides or pesticide family tested include atrazine, pyrethroids, chlorpyrifos, diazinon, and a limited number of organophosphates/carbamates. These pesticides are, or were, used in lawn care and homeowner pest control. The use of diazinon for lawn care or homeowner pest control is no longer approved. Detections were few, all were in low concentrations. TCEQ continued urban pesticide monitoring through 2010. TCEQ expanded the monitoring to include springs. TCEQ added pesticides that were not monitored before. 2010 TCEQ began monitoring golf courses. TCEQ monitored the primary cotton crop area in the southern and central portions of the Panhandle. The results of this study showed that pesticides have limited impact on groundwater. There were very few detections of atrazine and diazinon and those detections were at very low concentrations. There were detected in trace amounts of 2,4-D and alachlor. 2011 In 2011, TCEQ monitored the Lower Rio Grande Valley and Corpus Christi areas, with only low detections in few wells. 2016 TCEQ monitored areas near apiaries (i.e., areas where bees are kept) in Central Texas for Pollinator Protection efforts, with few low detects of the few pesticides analyzed. 2018 TCEQ monitored the I-35 corridor from Round Rock to Waxahachie, with just a few detections at low levels. Pesticide monitoring continued through 2023. Results from the last two years showed isolated detections near 3 ppb in the Panhandle Region. Most detections were low and scattered across the state. Trace amounts of atrazine were found in the Central Panhandle PWSs. During previous sampling detections in this area were close to the MCL of 3 ppb. Well owners and pesticide applicators can make corrections and avoid or reduce potential contamination in the future. Please refer to How Do You Prevent Pesticide Contamination of Private Water Wells? ( which provides more information on common ways to avoid contaminating a water well and groundwater. State and local agencies are working hard to protect the state’s water resources and water quality for the present and the future. With the help of educated, caring citizens, together we can protect, conserve, and ensure clean drinking water for generations of Texans to come. References Texas State Management Plan for Prevention of Pesticide Contamination of Groundwater (TCEQ SFR-070/01), Protecting the Environment Using Integrated Weed Management in Lawns (AgriLife Extension L-5324), Websites Texas Groundwater Protection Committee, Agricultural Chemicals Subcommittee historical records, Pesticides, Texas Department of Agriculture Pesticide Program, TCEQ Pesticides and Groundwater, · Tex*A*Syst website, Tex*A*Syst publication (especially B-6025), “Tex*A*Syst: Reducing the Risk of Ground Water Contamination by Improving Pesticide Storage and Handling,” Other Frequently Asked Questions (FAQs) To find additional FAQs visit the Texas Groundwater Protection Committee’s FAQ webpage at
  • Have Radionuclides Been Detected in Texas Groundwater?
    Radionuclides are types of atoms that are radioactive. The most common radionuclides in drinking water are radium, radon, and uranium. Most of the naturally-occurring radionuclides emit alpha particles. In 1974, the United States Congress passed the Safe Drinking Water Act. This law requires the U.S. Environmental Protection Agency (EPA) to determine the safe levels of contaminants in U.S. drinking water. The EPA conducts research of drinking water to determine the level of a contaminant that is safe for a person to consume over a lifetime and that a water system can reasonably be required to remove from it, given present technology and resources. This safe level is called the maximum contaminant level (MCL). Some treatment technologies include reverse osmosis, ion exchange, and aeration. Radionuclides have been found in some Texas aquifers. The U.S. EPA has set the MCL of gross alpha radiation in drinking water at 15 picocuries per liter (pCi/L). Most of the groundwater in Texas with gross alpha radiation greater than the MCL is found in the Hickory Aquifer in Central Texas (Figure 1) and the Dockum Aquifer of West Texas (Figure 2). The Edwards-Trinity Plateau (Figure 3), Gulf Coast (Figure 4), and Ogallala (Figure 5) aquifers also have a significant number of wells with high levels of gross alpha radiation. Although contamination from human activity can be a source of radionuclides, most of the radionuclides found in Texas groundwater occur naturally within the aquifer’s geologic formation. References: Water for Texas 2007, Texas Water Development Board, pages 228 – 229, Major and Minor Aquifers of Texas maps, (under the “Natural Features” heading) Drinking Water Problems: Radionuclides, Texas AgriLife Extension Service, B-6192 (English), B-6192S (Spanish), Commonly Encountered Radionuclides, U.S. EPA, Safe Drinking Water Act, U.S. EPA, For additional Frequently Asked Questions (FAQs) related to groundwater quantity, groundwater quality, septic systems, water wells, administrative entities, and publications, visit the Texas Groundwater Protection Committee’s FAQ webpage at
  • How Do You Prevent Pesticide Contamination of Private Water Wells?
    Texas Groundwater Protection Committee FAQs January 2024 How Do You Prevent Pesticide Contamination of Private Water Wells? Pesticides have been detected in groundwater in both urban and rural areas throughout the state where low levels of atrazine, diazinon, 2,4-D, and metolachlor are the most common pesticides found. In some areas greater concentrations have been detected, triggering further investigation. Monitoring for pesticides in groundwater can identify potential problem areas and allows state and federal agencies to efficiently focus limited resources. Statewide cooperative monitoring efforts for pesticides is ongoing, with most pesticide detections resulting in very low concentrations. However, only a limited number of pesticides are monitored due in part to budget limitations. Several issues concerning pesticides and groundwater became apparent because of these monitoring programs. Most sites where agricultural pesticides were detected in groundwater result from mixing and loading of pesticides in facilities located near water wells. Several of the investigated wells were old, corroding water wells that had been abandoned or improperly plugged or were located near such wells. Several detection sites were also associated with seasonal surface water features such as playa lakes and intermittent creeks. Along with the Texas A&M AgriLife Extension Service (AgriLife Extension), TCEQ provides education and outreach to agriculture producers and water well owners in the state. The legal system of the United States considers the product label a legal document. Improper use or misapplication of a pesticide can be punishable by fine or pesticide license revocation. In addition, some of the problems with pesticide application could be improved with better adherence to produce labeling County AgriLife Extension Agents, the Texas Department of Agriculture, or your pesticide distribution/sales representative have additional information on the proper use of pesticides. Well owners should check water wells on their property to ensure safe use of pesticides near the well. Avoiding or minimizing potential groundwater contamination can be prevented when well owners and pesticide applicators are aware of problems and ways in which pesticides can migrate into groundwater. How Can I Protect My Private Water Well? The most common ways to avoid contaminating a water well or groundwater include the following practices: Follow best management practices and the pesticide’s label instructions when locating a domestic water well near crop land or gardens. Locate pesticide storage, mixing, loading, and cleanup areas using the pesticide’s label instructions and best management practices guidance on the recommended distance from a water well. Build a secondary containment structure to prevent spills from draining into the well and wellhead area. All faucets used for this purpose should have a backflow preventer. · Avoid creating conduits that allow surface water to enter groundwater (i.e., do not locate trenches, burn pits, excavations, tailwater ponds, or septic systems near a water well). Read and understand the pesticide label for proper use. If you have questions, contact your county AgriLife Extension Agent or pesticide distribution/sales representative for clarification. Make sure that your water well is in good condition by checking and testing it regularly. Refer to the list of references below for information regarding well protection and the proper maintenance of water wells. Create a pesticide management program that includes the following information: The location of your water well(s) and any nearby underground conduit locations, surface drainage, or ponding areas. Your water well’s age, depth, diameter, screened interval, water table depth, pump information, etc. The location of any other nearby wells, especially any abandoned water wells, petroleum production wells, exploration wells, or disposal wells. Typical signs of wellhead or casing deterioration. Previous land use and the location of potential sources of contamination, both on your property and on adjacent properties. The location of crop or garden areas and other pesticide application areas. The soil type, underlying aquifer(s), and local topography (i.e., the lay of the land that would indicate the source and direction of runoff). Non-pesticide alternatives, such as hand weeding and beneficial insects. Contact information (names, phone numbers, and websites) related to pesticides, water wells, water quality, and the closest groundwater conservation district (for information regarding your aquifer characteristics and limitations). Proper pesticide use, best management practices, and knowledge of local water dynamics can help protect your drinking water and your family’s health, as well as safeguard the state’s groundwater resources. Your state and local agencies are working hard to protect the state’s water resources for the present and the future. With the help of informed, caring citizens, together we can protect, conserve, and ensure clean water for generations to come. Resources and Useful Links Texas State Management Plan for Prevention of Pesticide Contamination of Groundwater (TCEQ SFR-070/01), Texas Department of Agriculture Pesticide Program, TCEQ Pesticides and Groundwater, Tex*A*Syst website, Tex*A* Syst publications, especially B-6025, Tex*A*Syst: Reducing the Risk of Ground Water Contamination by Improving Pesticide Storage and Handling, and, Tex*A*Syst publications, B-6024, Tex*A*Syst: Reducing the Risk of Ground Water Contamination by Improving Wellhead Management and Conditions, U.S. Environmental Protection Agency (EPA) Introduction to Integrated Pest Management, U.S. EPA Drinking Water and Pesticides, Other Frequently Asked Questions (FAQs) To find additional FAQs visit the Texas Groundwater Protection Committee’s FAQ webpage at
  • Where Can Uranium Be Found?
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