MARGARET WHITE SPRINGS RECHARGE STUDY, BUFFALO NATIONAL RIVER, NORTH-CENTRAL ARKANSAS, USA

Margaret White Springs (MWS) is one of the largest springs in the middle section of the Buffalo National River (BNR), and contributes several tens of cubic feet of flow to river discharge on average, yet the source of the water is a point of debate. The spring is located 4 miles downstream of Robertson Hole, a losing reach of the river. At Robertson Hole the river loses a significant amount of flow to groundwater, up to 100% during the summer. Flow is re-established at MWS; interestingly, the resurging discharge has been measured as exceeding that lost at Robertson Hole. Determination of recharge areas to MWS is critical for understanding the hydrology of the spring and management of water resources along the BNR middle reaches. The majority of the river watershed lies within the karst terrain of the Springfield and Salem Plateaus, and surface to subsurface flow system is complex. Flow directions are difficult to predict, and groundwater flow paths often cross surface divides. Dye tracing methods were performed during three storm events to try to determine flow paths and delineate the recharge area to MWS. The three dye traces took place in areas outside the local surface watershed for MWS to determine if flow paths were crossing topographic divides. The results of the dye traces provided no indication that the areas chosen for dye injection contribute water to MWS. Specific conductance measurements were also taken at MWS, springs in the surrounding area, and the BNR at Woolum (upstream from MWS, near Robertson Hole). Mixing models using these data show a seasonal change in conductance values and indicate that not all MWS recharge originates at Woolum, consistent with previous discharge measurement comparisons.