Texas is such a large state and so diverse in its groundwater resources that the specific location of the subject property has a significant impact on both the information available about the location, as well as the ability to develop resources at a given location.
Major and Minor Aquifers
Texas has numerous aquifers capable of producing groundwater for households, munipalities, industry, farms and ranches. The Texas Water Development Board recognizes 9 major aquifers (aquifers that produce large amounts of water over large areas, viewable on the major aquifers map) and 21 minor aquifers (aquifers that produce monro amounts of water over large areas or large amounts of water over small areas, viewable on the minor aquifers map).
TWDB's Water Data Interactive System contains raw well data, available for visual review online. The database contains records of registered wells which have been assigned state well numbers and provides information and key facts including the geological formation serving the well, the status of the well (functioning / plugged, etc), the depth of the well, water quality, and other details that my help a driller gain indicators about general well viability and estimate drilling costs.
Over time, TWDB has inventoried nearly 140,000 water wells (inlcuding ~2,000 springs), and monitors groundwater quality through periodic sampling. Cooperating with nearly 50 groundwater conservation districts, federal entities, and municipalities, the TWDB provide guidance to well owners who depend on well water for drinking purposes, and serve as a resource for connecting the public with drillers and other service providers for services such as well disinfection.
Property owners are advised to start well projects by first calling the TWDB at 512.936.0871, to provide the approximate GPS coordinates for the subject property. The TWDB will be able to help advise on the nearest geological formation serving the property, the approximate depth a driller might have to go to access the desired aquifer, as well as which resource (if there are multiple available) would be the best potable source for household or irrigation use.
Myths About Wells
Contrary to popular belief, the existence of wells in a given nearby location does not automatically mean that an individual homeowners will have success drilling on their own property -- at least not within a budget an individual homeowner might find affordable. Typical water well depths for private wells are generally above 1,000 feet. Deeper (2,000 - 3,000+ feet) and wider bores (such as those that serve community and special water districts, can easily run into hundreds of thousands of dollars.
Well performance can also vary widely by proximity to each formation, so the distance of even 50 yards can make a big difference in well performance and viability, even between nextdoor neighbors. Further, "hitting water" doesn't mean the source is potable, or sustainable through periods of lower rain activity and drought. Shallow resources can be depleted quickly, and the threat of diminished supply increases when shallow resources are shared, which is a common occurance in smaller communities and colonias throughout Texas.
An additional observation is to consider that not all private wells are registered. A homebuyer is well advised to research an existing well on a given property prior to buying it.
Mortgage Lending and Wells
On a final note, property buyers will find that Lenders also have quite a bit to say on the subject of wells and water resources. Those shopping for rural properties and vacant lots or land will want to inquire about any capacity conditions (gallons per hour, or number of households served from a community resource, water quality, and testing requirements) that might govern a lender's approval of property condition, particularly if FHA, VA, and USDA financing is utilized.
The ability to access cooperative and municipal resources is a highly desirable attribute when shopping vacant land, and should be a consideration in search criteria.