THE SOUTH ARKANSAS CRITICAL GROUNDWATER AREA: HISTORIC WATER LEVELS AND CURRENT TRENDS

The Sparta aquifer, also known as the Memphis aquifer or the Middle Claiborne, is a tertiary-aged water bearing formation composed mainly of sand. The formation outcrops along the western edge of the Mississippi Embayment in Southern Arkansas and is overlain by the Mississippi River Valley alluvial aquifer throughout Central and Northeastern Arkansas. The Sparta is the thickest sand unit in the Mississippi Embayment system, ranging from zero to 200 feet along the outcrop and up to 900 feet in the southeastern part of the state.

The Sparta is an important source of groundwater for southeastern Arkansas. It is the primary aquifer in Union County, Arkansas. Most of the public and industrial water supply has relied on the Sparta as their water source.

Historically the Sparta has been declining beneath the major population centers of El Dorado and Magnolia, Arkansas. Withdrawals from the aquifer have exceeded the natural rate of recharge leading to the development of a cone of depression in Union and Columbia counties. In response to declining water levels, the Arkansas Soil and Water Conservation Commission in 1996 declared five counties in Arkansas "critical groundwater areas." In 1999 the Arkansas legislature passed Act No. 1050 authorizing the creation of groundwater conservation boards in counties designated as critical groundwater areas.

Following the passing of Act No. 1050, the Union County Water Conservation Board began the process of regulating groundwater use within the county. A Water System Master Plan was developed to determine how to best serve the long-term water supply needs of the County. A decision was made to supply water directly from the Ouachita River to limit the need for the use of groundwater. Recent data indicates positive change in water levels which can be at least partially attributed to this conjunctive water use management strategy.

This presentation will review current monitoring efforts and trends in comparison with historic water levels of the Sparta in South Arkansas to attempt to quantify the effectiveness of these remediation actions.