Madison, Wisconsin: Water Resources Center, University of Wisconsin–Madison
An ongoing series of natural gradient tracer tests are being conducted in Wisconsin's central sand plain, a region of thick sandy glacial outwash. The initial motivation for the tracer tests was to determine the flow path around a drainage ditch in order to evaluate the role of ditches in limiting the spread of agricultural contamination. The tests were also designed to permit a detailed evaluation of the tracer movement within the aquifer. These tracer tests involve the simultaneous introduction of bromide and iodide tracers, each at a different depth, up-gradient of the ditch. The path of the tracer is monitored by frequent synoptic sampling from a dense three-dimensional array of multilevel sampling wells.