The major aquifers of the EUWCD are

• the Carrizo-Wilcox Aquifer spanning from the northern boundaries of Frio, Atascosa, and Wilson counties to the southern boundaries of the same counties. The Carrizo-Wilcox Aquifer also occurs in the north part of Karnes County.

• the Gulf Coast Aquifer System in Karnes County.

The minor aquifers in EUWCD are:

•  the Queen City Aquifer in Frio, Atascosa, and Wilson Counties;

•  the Sparta Aquifer in Frio, Atascosa, and Wilson Counties; and

• the Yegua Jackson Aquifer in southern Atascosa and Wilson counties and Karnes County.