KARST HYDROGEOLOGIC RESEARCH IN THE UPPER MIDWEST OF THE UNITED STATES

Support of student research was one of the cornerstones of Dr. Nick Crawford’s hydrogeology laboratory at Western Kentucky University. For master’s thesis work, Dr. Crawford provided advice, training in dye trace protocols and analysis, and access to the many hydrogeological reports he produced in his work and applied research all of which provided the basis for the thesis research of many WKU graduate students. This paper provides an example of such work that identified the source and movement of agricultural contaminants in a karst groundwater basin which straddled northeast Iowa and southeast Minnesota. Qualitative and quantitative dye tracing resulted in the delineation of the Coldwater Cave Groundwater basin and determined hydrologic flow paths within the basin. Investigation of basin and aquifer characteristics and evaluation of cave map data, and karst feature inventories established the relationship between surface and subsurface hydrogeology. Water sampling and analysis documented the quality of the surface water and groundwater within the basin. The sources of nitrates, bacteria, and pesticides were determined using isotopic analysis, ribotyping, and general water quality testing. Review of data collected by other researchers during different flow and climate conditions and integration of that data with the dataset for this study allowed a comparison of base and high level groundwater flow. Analysis of cave and surface stream temperatures, hydrograph data, and climate records confirmed the relationship between surface climate and cave climate and illustrated the seasonal nature and event-dependence of groundwater flow and agricultural pollution. Evaluation of land use within the basin quantified the amount and type of agricultural land use. The results of the study identified the sources of agricultural contaminants, showed their effect on water quality, and documented that contaminant transport in shallow karst groundwater basins was a function of climate, hydrogeology and land use. The multidisciplinary nature of this thesis research was inspired by Dr. Crawford’s approach to applied hydrogeological work.