Ground-water resources of Brazoria County, Texas.

The Chicot and Evangeline Aquifers are the only hydrologic units bearing fresh (less than 1,000 milligrams per liter dissolved solids) or slightly saline water (1,000-3,000 mg per liter dissolved solids) in Brazoria County, Texas. These aquifers are composed of gravel, sand, silt, and clay of Pliocene, Pleistocene, and Holocene age. The average permeability of the Evangeline Aquifer is about 250 gpd per square foot. The Chicot Aquifer has a range of permeability from 130 to 1,655 gpd per square foot. A large cone of depression occurs in the water-level surface as a result of pumping from the upper part of the Chicot in the Brazosport area of southern Brazoria County. Land-surface subsidence of more than 1.5 feet, attributed mostly to groundwater removal, has taken place in northeast Brazoria County. Groundwater pumpage for all uses in 1967 was 43 mgd. of this, 22.6 mgd was used for irrigation, 12.7 for industrial use, and 7.7 mgd for public and domestic supplies. The fresh groundwater potential of the Brazosport area is fully developed or overdeveloped while in some areas of northern Brazoria County, it is relatively undeveloped.