Several dams throughout the United States have been built on karst terrains, where soluble limestone bedrock has been dissolved to form features such as caves, sinkholes, and underground rivers. In such karst regions, subsurface hydrology can play an integral role in the condition, operation, and safety of dams and should be considered during risk assessment. Patoka Dam, near Jasper, Indiana, is situated on a well-developed karst landscape/aquifer system, faces significant potential challenges, and recently underwent risk assessment. A groundwater flow investigation using multiple fluorescent tracer tests, analysis of water-table elevations, isopach mapping of the Glen Dean Limestone, and spring hydrograph analysis was performed to better understand local groundwater hydrology in the vicinity of the existing water-control structures. Dye-tracing results identified the local flow direction as south to north and the mean dye travel time from injection locations to Robert Hall Cave Spring (RHCS) as 8- 11 feet per hour. These results also indicate that groundwater is bypassing the control structures in the vicinity of the cut-off wall, but the geometry of these flow paths is not clear. The recharge area for RHCS, a significant groundwater discharge point downstream from Patoka Dam, was delineated and the existence of a groundwater divide in the area of the dike was confirmed. The location of this groundwater-basin boundary follows an estimation of where the Glen Dean Limestone outcrops along the perimeter of the dissected ridge that lies between Patoka Lake and RHCS. Spring hydrograph analysis shows that spring discharge is primarily influenced by local precipitation events. However, precipitation events can result in increased pool elevation making the relationship between spring discharge and pool elevation unclear within the data set. This groundwater investigation has provided a clearer characterization of the hydrogeology within the vicinity of Patoka Dam. In combining the various hydrogeologic results, some insight into the function and geometry of the local karst network that could potentially affect the integrity of the dam and/or dike structures has been provided.