SPATIAL CHARACTERIZATION OF HYDROCHEMISTRY FOR THE ALLUVIAL AND SPARTA AQUIFERS OF THE GRAND PRAIRIE REGION, EASTERN ARKANSAS

Saline water contamination of aquifers in eastern Arkansas has been an historical problem and will likely expand in the future. In the Grand Prairie region, depressions in the potentiometric surfaces of the Alluvial and Sparta aquifers have resulted from significant agricultural, municipal, and industrial use. Increased chloride concentrations may result, in part, from upconing and intrusion. Spatial analysis of hydrochemistry from the Alluvial and Sparta aquifers in eastern Arkansas provides data to better characterize areas and sources of saline water contamination.

During the summer of 2000, 77 water samples were collected from the Alluvial aquifer and 40 from the Sparta aquifer. Initial results show a relationship between areas of significant ground-water level decline and areas of high specific conductance and high chloride concentration in both aquifers. In the Alluvial aquifer, specific conductance ranged from 70 to 1,597 µS/cm and chloride concentrations ranged from 4 to 172 mg/L, with higher concentrations found in areas of greatest water-level decline. For the Sparta aquifer, specific conductance ranged from 47 to 741 µS/cm and chloride concentrations ranged from 2 to 56 mg/L, with higher values also found in the area of significant water-level decline.

Analysis of water-quality data aids in determination of source(s) of contamination and interpreting relationships between the areas of most significant ground-water level decline and observed water-quality variations. Relational patterns between the Alluvial and Sparta aquifers were also examined. Results from this study supply agricultural communities with baseline water-quality data and are beneficial in best management strategies for agricultural, municipal, and industrial users.