TEMPORAL VARIABILITY OF THE RIVERBED CONDUCTIVITY DURING STORM EVENTS AT A SITE OF INDUCED INFILTRATION

River Bank Filtration (RBF) is considered to be an efficient and relatively low-cost technology for producing drinking water. This method can remove and/or aid in the degradation of contaminants in surface water as it infiltrates through the riverbed into an aquifer, and subsequently to the production wells. In some settings the most important component of this method is the colmation layer – the first few centimeters of the riverbed characterized by relatively low hydraulic conductivity and high biological activity. One of the biggest concerns regarding the effectiveness of RBF systems to facilitate a production of the good quality drinking water is an impact of storm events on the riverbed hydraulic conductivity. During high river stage scour of the colmation layer can increase the hydraulic conductivity of the riverbed. This study applies groundwater- and heat-flow modeling using USGS software, VS2DH, to determine potential changes in the riverbed hydraulic conductivity resulting from scour or deposition during storm events. The research field area is located along Great Miami River at Charles M. Bolton Well Field in southwest Ohio. To collect the data necessary for modeling, the field site was instrumented with a network of shallow piezometers equipped with transducers to measure subsurface water levels and temperatures. River temperature and stage data were also collected with a transducer. Riverbed hydraulic conductivity was estimated through model calibration. Values were varied during simulated storm events to better match the simulated and observed temperatures and hydraulic heads in the monitoring wells. River scour and deposition were directly monitored by using four Roctest® vibrating-wire total-pressure cells (load cells) installed about 60 cm below the riverbed surface in the close proximity to the riverbed piezometers. We expect that the riverbed scour during the storm events resulted in increased hydraulic conductivity of the riverbed, and that the riverbed hydraulic conductivity decreased again due to deposition during the falling limbs of the storm events.