Abstract: Subsurface Stratigraphy and Water Resources of the Dothan Area, Houston County, Alabama

Abstract

ABSTRACT The city of Dothan is located in northwestern Houston County in the extreme southeastern corner of Alabama. Currently, water is supplied to the Dothan area through 30 wells whose screened intervals vary in depth from 100 to 1,080 feet. During 1997, these wells supplied about 19.4 million gallons of water per day to a population of about 75,000 citizens. Prior to the 1997 completion of geological investigations conducted in support of a wellhead protection program for Dothan's water supplies, the probable source(s) of Dothan's water was poorly known. Guesses based primarily on drillers' logs or a combination of well depth integrated with the regional dip of stratigraphic units were invariably incorrect or involved multiple geological units as possible sources. The most fundamental question--"From which unit is our water being produced?"--could not be answered. In order to define the stratigraphy of the area, over 14,000 feet of samples from 11 wells, including two deep oil and gas test wells, in the Dothan area were microscopically examined and described in detail. These data were then integrated with available electric logs. The resulting stratigraphy was used to define the subsurface geology of over 50 additional area wells lacking sample or log control. This stratigraphy defined the precise locations of screened intervals within individual formational units. The construction of a series of strike and dip cross sections, as well as isopach and structure contour maps, for the approximately 150-square-mile study area, also delineated major and minor aquifers and their associated boundary confining units, documented their areal facies and thickness changes, and permitted the projection and characterization of potential aquifers below current production zones.