The saturated thickness of the Edwards-Trinity aquifer system exceeds 1,000 feet in the southern part of the aquifer system and thins to less than 100 feet near the northern limits. The Edwards- Trinity aquifer system of west-central Texas is composed primarily of Cretaceous limestone and dolomite. The three aquifers comprising the aquifer system are the Edwards aquifer of the Balcones fault zone, the Trinity aquifer of the Balcones fault zone and Hill Country, and the Edwards-Trinity aquifer of the Edwards Plateau and Trans-Pecos. The two confining units within the aquifer system are the Hammett and the Navarro-Del Rio confining units, neither of which is laterally extensive throughout the entire aquifer system. The saturated thickness was determined by subtracting the altitude of the base of the aquifer system from the altitude of the historical potentiometric surface. Variations in saturated thickness result from variations in the altitude of the base of the aquifer and the altitude of the historical potentiometric surface. Troughs and ridges on the pre-Cretaceous surface upon which the aquifer system rests affect the thickness of saturation. The potentiometric surface is depressed in areas of stream dissection, resulting in less saturated thickness in these areas.
Additional publication details
USGS Numbered Series
Historical saturated thickness of the Edwards-Trinity aquifer system and selected contiguous hydraulically connected units, west-central Texas
Water-Resources Investigations Report
2 maps on 2 sheets : col. ; 28 x 46 cm. and 58 x 91 cm., both sheets 66 x 92 cm., folded in envelope 31 x 24 cm.