Knoke, Kevin Lyle2020-04-212020-04-211999-12http://hdl.handle.net/11299/212456A Thesis submitted to the faculty of the Graduate School of the University of Minnesota by Kevin Lyle Knoke in partial fulfillment of the requirements for the degree of Master of Science, December 1999.For over a century there has been concern over the adverse effects that the water from the Dakota Aquifer has on the unconfined Sheyenne Delta aquifer of North Dakota. High concentrations of NaCl and Na2SO4 often render water of the Dakota Aquifer unfit to drink. The purpose of this thesis was to gain a better understanding of the physical and chemical processes influencing ground water chemistry at a site in which mixing of waters from both the Dakota and the Sheyenne Delta aquifers has occurred. Located in the northwest corner of Ransom County of southeastern North Dakota, the research site centers around a free flowing Dakota Aquifer well that is impacting the surficial Sheyenne Delta Aquifer. The areal extent of the contaminant plume (mixed Dakota and Sheyenne Delta Aquifer water) was determined using electrode resistivity after which monitoring wells were installed. Groundwater samples were collected and submitted for analysis of major cations and anions. Following statistical analysis of samples for quality control measures, the distribution of major cations and anions was evaluated by contour concentrations. The USGS geochemical modeling software NETPATH was used to determine the amount of evaporative concentrations of Dakota Aquifer water prior to infiltration into the Sheyenne Aquifer and the degree of dilution with fresh water is evaporatively concentrated 2.35 times as it infiltrates. Concentrations of chloride Cl- and sulfate SO42-, as well as other major ions, show that the plume of brackish water is concentrated near the water table at and a short distance down gradient from the infiltration point. With continued transport distance, the plume mixes vertically with water of the surficial aquifer and is diluted. The average change in concentration is 79.29 mg/l per meter of linear distance from the infiltration point.enPlan As (thesis-based master's degrees)Department of Earth and Environmental SciencesUniversity of Minnesota DuluthMaster of ScienceMaster of Science in GeologyThesis or Dissertation