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 Flow System Study
The ground-water flow-system study was designed to track the transport of nutrients and pesticides from a field where they were applied, through the shallow flow system that underlies the field and the adjacent forested floodplain/wetland, to areas of discharge to the surface-water system. During previous studies of a 1,000-acre field, nutrients and pesticides were measured in two shallow ground-water monitoring wells adjacent to and down-gradient from the field. Three generalized flow paths were identified within the study area: 1) shallow ground water collected by a network of tile drains within the field that discharged to ditches; 2) shallow ground water flowing from the farmed upland area and discharging along the toe slope at the edge of the forested flood plain; and 3) shallow ground water flowing from the farmed upland area, through the alluvial sediments within the flood plain, and discharging directly to the stream. Sampling points were located along two transects from edge of field to stream. Shallow monitoring wells were installed at each sample point, including points adjacent to the stream and within the stream bed; lithologic information was recorded; and water samples were collected and analyzed from each well and from the stream. Based on an evaluation of those data, additional sample locations were selected to provide better characterization of the system. These included additional wells installed along the transects between existing locations, nests of wells installed at varying depths at existing locations, springs located along the base of the toe slope that separated the forested upland from the forested flood plain, and three pipes connected to a network of tile drains throughout the field that discharged into two drainage ditches that flowed through the flood plain. The complete network of sample locations included 34 wells, 3 springs, 3 drains, and 2 surface-water sites. The frequency of sample collection and the list of constituents analyzed in water samples varied, but a core of sites were sampled 3 times a year to represent different seasons and flow conditions. Most samples were analyzed for nutrients, pesticides, major ions, and organic carbon. On-site measurements of water levels, flows, and field parameters also were made during each visit.