ISOTOPIC ANALYSIS OF MARGARET WHITE SPRING ON THE BUFFALO NATIONAL RIVER

Margaret White Spring in St. Joe, Arkansas emerges within the channel of the Buffalo National River and contributes several tens of cubic feet of flow to river discharge. The spring is located about 4 miles downstream from a reach of the Buffalo River—referred to as Robertson Hole—in which the river loses a considerable quantity of flow (up to 100% during dry periods) to groundwater. More water reappears at Margaret White Spring than is lost from the river in the losing reach, and data are being collected to quantify the contribution of water originating from that lost from the river channel, water originating from other groundwater flow paths, and water from recent rainfall . Rainfall samples were collected, and spring and river samples were collected during low, peak, and falling points on the hydrograph to obtain a broad picture of the effect of rainfall on the composition of the river. Water δ²H and δ¹⁸O isotopic ratios, water temperature, and general water-chemistry data will be determined and used to assess spring water sources. Groundwater samples from nearby springs and rainwater samples were collected to provide representative information on end-member compositions. Another sample was collected one hundred yards downstream from the springs to capture the composition of the mixed flow. Preliminary data—primarily temperature data—indicate a significant groundwater contribution at Margaret White.