This data release pertains to a seepage investigation and dye tracing study conducted in the Big Creek watershed of Newton County, Arkansas. The seepage dataset includes geospatial files of discharge measurement points and zero-flow observations along with vector lines delineating losing and gaining stream reaches. Hydrologic systems in karst environments have a high degree of interconnectivity between surface water and groundwater systems. Because of this interconnectivity, activities which occur on the surface in karst environments have a direct impact on the water quality and quantity of karst groundwater. The Ozark Plateaus Physiographic region (Ozarks) of northern Arkansas and southern Missouri is an extensive karst area where many of the karst flow systems are recharged via losing streams. Losing streams are where stream flow sinks or loses into the subsurface, either along a reach or potentially at a discrete point. This flow may reappear further downstream within the same drainage or may follow karst pathways (such as fractures and conduits) to springs, caves, or other drainages. Thus, in karst areas with losing streams, awareness of the locations where stream flow is lost or gained is necessary to properly understand the karst hydrologic system and the influences on water quality. In addition to quantifying stream flow losses and gains, knowing the pathway(s) that the sinking water follows is necessary as karst flow paths are unpredictable. Dye injections of fluorescent tracer dyes can be conducted to trace the sinking water to resurgences that can be monitored. Big Creek in Newton County, Arkansas is the fifth largest tributary to the Buffalo National River by land area. The creek is comprised of two primary streams, Big Creek and the Left Fork of Big Creek, both of which have significant reaches underlain by Mississippian Boone Formation, a limestone unit that is commonly karstified. On October 13-14, 2020 a seepage investigation was conducted in the Big Creek watershed to determine, during base flow conditions, where losing and gaining reaches of the streams were located. The study focused primarily on the two main streams, Big Creek and Left Fork of Big Creek; however, many tributaries were examined dependent on road access. The seepage investigation was conducted over two days, a 28-hour span, and resulted in 13 discharge measurements along the main streams and 48 zero-flow observations at tributaries and on main streams. Following the seepage investigation, a network of 27 monitoring sites were established to locate charcoal packets used in the detection of fluorescent tracer dyes. On October 15, a dye injection of fluorescein was conducted along the Left Fork of Big Creek into a flowing reach upstream from a completely dry reach. The dye was detected 2.9 miles downstream from the injection site along the next gaining stream reach and at subsequent monitoring sites downstream from the initial recovery site. For more detailed methodology on groundwater tracing see Process Steps within the metadata for the dye tracing dataset.