The Texas Water Development Board recognizes the occurrence of one major aquifer, the Carrizo-Wilcox aquifer, and one minor aquifer, the Queen City aquifer, within Rusk County.
Of these aquifers, the Carrizo-Wilcox aquifer is the most important and productive aquifer in Rusk County, historically supplying most of the groundwater produced within the county.
The Carrizo-Wilcox major aquifer is bound below by the marine deposits of the Midway Group and above by the Reklaw Formation.
The marine deposits of the Midway Group represent a lower confining unit for the aquifer throughout its extent, while the predominantly glauconitic clay sediments of the overlying Reklaw Formation represent an effective upper confining unit for the aquifer in its subcrop.
In Rusk County, much of the Carrizo-Wilcox aquifer occurs in outcrop. These outcrop areas serve as recharge zones for the downdip deep-lying sands of the aquifer in its subcrop. In its outcrop in the east-central portion of Rusk County, the Carrizo-Wilcox aquifer is often only represented by strata of the Wilcox Group.
As the Wilcox sediments are predominantly comprised of fluvial and deltaic sands distributed among lower permeability interchannel silts and muds, the Wilcox portion of the Carrizo-Wilcox aquifer can be characterized as a multi-aquifer system.
As opposed to the Carrizo aquifer, which can be characterized as a relatively homogenous, single aquifer system, the complex multi-aquifer system of the Wilcox requires an accurate description of both the arrangement of the various lithofacies (i.e., sand body distributions) and associated hydraulic properties in order for the groundwater availability of the aquifer system to be properly modeled and understood.
Although considerably less important in Rusk County than the Carrizo-Wilcox aquifer, the Queen City minor aquifer is an important local source of groundwater primarily in its outcrop in the northwestern portion of Rusk County and in the Mt. Enterprise Fault System in the southwestern portion of the county.
The Queen City aquifer’s limited extent and shallow occurrence in Rusk County make it a target for primarily low-yield production. In addition, its generally poorer water quality than the Carrizo-Wilcox aquifer makes it a less desirable target for production and use as a primary drinking water source in Rusk County.
Another limited source of fresh groundwater in Rusk County is the Sparta aquifer. The Sparta aquifer provides small amounts of fresh groundwater to shallow, primarily low-yield wells in its outcrop within the Mt. Enterprise Fault System in southern Rusk County.
Although the Sparta aquifer is recognized as a minor aquifer in other parts of Texas, the Sparta aquifer is not considered a minor aquifer in Rusk County due to its limited areal extent and its discontinuity with other Sparta Sand sediments outside of the Mt. Enterprise Fault System and Rusk County.
As a result, the Sparta aquifer in Rusk County is not considered a significant source of groundwater for purposes of regional water planning and, thus, is not considered during regional-scale groundwater availability modeling.
*Information on the geologic units and their water-bearing properties within Rusk County is available in the District’s Management Plan, located in the District Documents section of the District’s website.
