Aquifers in the LPGCD

The LPGCD manages aquifers in the Bastrop and Lee Counties with the primary groundwater resource being the Carizo-Wilcox Aquifer. All of the aquifers in the District serve ecological, cultural, and economic significance to the state and the Bastrop and Lee Counties. In addition to managing these aquifers, the LPGCD continuously studies them to adapt management techniques in response to increasing demand and a changing climate.

Overview of the Aquifers

A key aquifer in the LPGCD is the Carrizo-Wilcox Aquifer, which includes the lower Hooper formation, the middle Simsboro formation, and the upper Calvert Bluff formation, forming a single hydrologically connected aquifer system. This major aquifer is the largest and most extensive in the LPGCD, with significant confined storage. The Carrizo formation, being the uppermost aquifer, is highly utilized by small wells and numerous wells for municipal purposes in cities such as Lexington, Smithville, and Giddings. The middle Simsboro formation is noted for its high productivity and is utilized by numerous wells and municipal water suppliers, producing large quantities of fresh to slightly saline groundwater.

Other aquifers within the LPGCD include the Queen City and Sparta aquifers, both classified as minor aquifers. The Queen City Aquifer, found in about half of the LPGCD, supports a large number of wells and municipal supplies, yielding small to moderate quantities of fresh to slightly saline water. The Sparta Aquifer, present in only a third of the district, also yields small to moderate quantities of water used for domestic and livestock purposes. Additionally, the district oversees several other aquifers, including the Colorado River Alluvium, Trinity, Yegua-Jackson, Midway Group, Reklaw, Weches, and Cook Mountain formations, each with varying degrees of usage and water quality.

Image of a stream of water pouring into a unit of water

Carrizo-Wilcox Aquifer

The Carrizo-Wilcox is defined by the state of Texas as 

one single major aquifer made up of four distinct units. 

Within groundwater conservation district 

management, the the four distinct aquifer units are 

managed separately. These units are the Carrizo 

Aquifer and three units within the Wilcox Group, which 

are the Calvert Bluff, the Simsboro Aquifer, and the 

Hooper Aquifer.

Carrizo

  • Major aquifer
  • Uppermost aquifer within the Carrizo-Wilcox Aquifer
  • Yields high quantities of fresh water
  • Used for domestic, irrigation, municipal purposes
  • Fine to coarse-grained massive sand


Calvert Bluff

  • Major aquifer
  • Uppermost aquifer within the Wilcox Group portion of the Carrizo-Wilcox Aquifer
  • Yields moderate quantities of fresh water
  • Used for domestic, irrigation, and municipal purposes
  • Low permeability silts and clays and lignite deposits that serve as confining layers that limit the vertical movement of groundwater
  • Also contains sandstone units that can yield moderate quantities of water

Simsboro

  • Major aquifer
  • Middle unit within the Carrizo-Wilcox Aquifer
  • Yields high quantities of fresh water
  • Formation is present in all of Lee County and the central to eastern Bastrop County
  • Fine to coarse-grained sand, with relatively small amounts of silt, clay, and mudstone

Hooper

  • Major aquifer
  • Lowermost aquifer within the Carrizo-Wilcox Aquifer
  • Yields low quantities of fresh water
  • Used for domestic and municipal purposes
  • Predominantly mudstone, with varying amounts of sandstone, and some thin lignite beds in the upper part of the formation
This is an image of water being pumped from a faucet outside

Sparta Aquifer

  • Minor aquifer
  • Yields small to moderate quantities of fresh water
  • Only in 1/3 of the LPGCD, primarily in Lee County
  • Used for domestic, livestock, and municipal purposes
  • Loosely cemented, sand-rich unit, with some interbedded silt and clay

Queen City Aquifer

  • Minor aquifer
  • Yields small to moderate quantities of fresh water
  • In 1/2 of the LPGCD
  • Used for domestic and municipal purposes
  • Massive to thin-bedded, fine- to medium-grainedsandstone with some silt, clay, shale, and lignite
Picture of a water well with moss growing in it

Yegua-Jackson Aquifer

  • Minor Aquifer
  • Present in only 1/3 of Lee County
  • Does not yield significant quantities of water
  • Very little use, primarily for domestic and livestocks

Trinity Aquifer

  • Major aquifer
  • Unused because extreme depth and poor water quality
  • No known wells in the District


Colorado Alluvium

  • Not currently classified as a major or minor aquifer, but defined as an alluvium
  • Yields significant quantities of water
  • Used primarily for agriculture and municipal use