Potentiometric surface of the Ozark aquifer in northern Arkansas, 2001

The Ozark aquifer in northern Arkansas comprises dolomites, limestones, sandstones, and shales of Late Cambrian to Middle Devonian age, and ranges in thickness from approximately 1,100 feet to more than 4,000 feet. Hydrologically, the aquifer is complex, characterized by disconnected and extensive flow components with large variations in permeability.

The potentiometric-surface map, based on 84 well and 6 spring water-level measurements collected in 2001 in Arkansas, indicates maximum water-level altitudes of about 1,359 feet in Carroll County and minimum water-level altitudes of about 241 feet in Randolph County. Regionally, the flow within the aquifer is to the south and southeast in the eastern and central part of the study area and to the northwest and north in the western part of the study area. Comparing the 2001 potentiometric-surface map with a predevelopment potentiometric-surface map indicates general agreement between the two surfaces. Potentiometric-surface differences could be attributed to differences in pumping related to changing population from 1990 to 2000.