South Atlantic Water Science Center - Georgia
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The Apalachicola-Chattahoochee-Flint (ACF) River National Water Quality Assessment (NAWQA) Program
ACF Study Design: Groundwater Land Use Studies
The agricultural land-use study was designed to determine the chemical quality of shallow ground water that underlies agricultural areas in a 6,700 sq mi area of the southern part of the ACF River basin. Sites for monitoring the surficial aquifer were located randomly using the computer program developed for the NAWQA program (Scott, 1990) and wells were installed according to NAWQA guidelines (Lapham and others, 1995) adjacent to and downgradient of 37 farm fields. Four reference wells were installed in forested areas to represent background water-quality conditions. The depth to the water table in the surficial aquifer monitoring wells ranged from about 3-67 ft below land surface. Surficial aquifers were selected for sampling rather than deeper aquifer systems because surficial aquifers are the first water-bearing zones to receive recharge from infiltration, and presumably are more susceptible to contamination. Therefore, water-quality conditions in surficial aquifers may serve as an early warning of potential contamination of deeper aquifer systems that are used for drinking-water supply and irrigation. Water samples were collected from all wells during summer 1993 and from most wells during spring 1994. The sample times represented low and high water-table conditions, respectively. The samples were analyzed for nutrients, pesticides, volatile organic compounds, major ions, organic carbon, and selected radionuclides. On-site measurements of water levels and field parameters also were made at each site.
The urban land-use study was designed to determine the chemical quality of shallow ground water that underlies Metropolitan Atlanta within a 350 sq mi area of the surficial drainage to the Chattahoochee River. Sampling sites were established by subdividing the study area into 30 polygons of equal area using the computer program developed for NAWQA (Scott, 1990), and then selecting an existing domestic or observation well, and where present, a spring, from each polygon. Forty locations were selected as sampling sites. Depth to water in the monitoring wells ranged from 2-29 ft below land surface. Each site was sampled once during the period from summer 1994 through spring 1995. Samples were analyzed for nutrients, pesticides, volatile organic compounds, major ions, organic carbon, trace metals, and selected radionuclides. On-site measurements of water levels, flows from springs, and field parameters also were made at each site.