RIDING THE WAVES IN OHIO: AN EVALUATION OF A NITRATE PLUME IN GROUNDWATER
Results indicate that the plume flow path is controlled by the locations of coarse sand and gravel deposits, likely deposited in paleo-river channels; these channels direct the groundwater flow along the northeast/southwest plume axis. However, the migration of maximum concentrations within the plume (toward and away from the river) is affected by "waves" created by dynamic interaction with precipitation infiltration and the accompanying rises in the river flood pool. Groundwater levels in the highly transmissive aquifer rise quickly (within hours) in response to infiltration, causing groundwater flow toward the river. As surface runoff raises the Ohio River flood pool, the groundwater gradients reverse and flow is away from the river. During non-precipitation periods, flood pool fluctuations result from routine lock releases, creating smaller "waves" of groundwater flow toward and away from the river. This understanding of groundwater flow dynamics is being used to describe the attenuation/migration of the elevated nitrate concentrations, in order to evaluate natural attenuation of the plume.