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 http://www.texasgroundwater.org/.

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 http://tgpc.state.tx.us/frequently-asked-questions-faqs/ .

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: http://www.twdb.texas.gov/groundwater/data/

• Texas Alliance of Groundwater Districts (TAGD) at: http://www.texasgroundwater.org/, and

• United States Geological Survey (USGS) at: http://waterdata.usgs.gov/nwis/gw.

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 http://tgpc.state.tx.us/frequently-asked-questions-faqs/.

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 http://www.tceq.texas.gov, the Texas A&M AgriLife Extension Service at http://texaswater.tamu.edu. the Texas Water Code at http://www.statutes.legis.state.tx.us/?link=WA, or the Texas Alliance of Groundwater Districts at http://www.texasgroundwater.org/.

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 http://tgpc.state.tx.us/frequently-asked-questions-faqs/.

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?

1. Special weather stations (see Figure 1) measure the parameters needed for the calculation of reference evapotranspiration (ETO).

2. The network calculates ETO which is used to determine plant water requirements and irrigation needs.

3. 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, http://TexasET.tamu.edu;

• WaterMyYard, http://watermyyard.org/;

• West Texas Mesonet Project, http://www.mesonet.ttu.edu/.

• TexMesonet, https://www.texmesonet.org/

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 https://tgpc.texas.gov/frequently-asked-questions-faqs/.

http://www.twdb.texas.gov/conservation/BMPs/Ag/doc/4.1.pdf