Evaluation of Groundwater Quality in Paleozoic Aquifers Using GIS Techniques, Central Texas

Abstract

Well data from the Texas Water Development Board (TWDB) covering Paleozoic aquifers surrounding the Llano Uplift of Central Texas have been processed using geographic information systems (GIS) to generate chemical distribution maps. These minor aquifers have not been studied in excess due to their location and low population density in the region. The aquifers, as of today, are not relied upon to supply municipalities with potable water unless surface water conditions are not favorable. Analyses of the aquifers major constituents were used to identify the dominant hydrochemical facies of the study area and locating distribution patterns for heavy metals that illustrate whether the sources are of natural or anthropogenic contamination. Any factors influencing the ionic concentrations were analyzed using the digital maps to quantify the geochemical and anthropogenic processes. Conducting comparative analyses of vertically stacked aquifers was utilized to determine the potential of cross -communication through leaky confining beds separating the units, including those of the Hickory Aquifer, Ellenburger– San Saba Aquifer, and Marbles Falls Aquifer.

Structural studies of the area based on spatial interpolation of lineaments indicate potential regions of enhanced vertical fluid flow and hydraulic connectivity between the aquifers. Temporal data dating back to the 1930s enabled evaluation of temporal changes in the minor aquifer's geochemistry through time. Assessing these data in conjunction with geochemical mapping indicates regions where fluid evolution within the Paleozoic aquifers has occurred and enabled the delineation of zones of potential connectivity within the Paleozoic aquifers of Central Texas. The use of GIS-based techniques has provided the ability to interpret broad-scale and local patterns that would be problematic when examining using point-to-point evaluations. Although this technology will not replace standard field and laboratory studies, it can provide time effective evaluations that supplement studies concerning water resources.

AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015