Investigating Riverbed Hydraulic Conductivity at Several Well Fields Along the Great Miami River, Southwest Ohio

Tuesday, April 21, 2009: 11:30 a.m.
Joshua Tree (Hilton Tucson El Conquistador Golf & Tennis Resort )
Jonathan Levy, Ph.D. , Geology, Miami University, Oxford, OH
Alicja Wojnar , Geology, Miami University, Oxford, OH
Samuel Mutiti , Geology, Miami University, Oxford, OH
The riverbed vertical hydraulic conductivity (Kv) is a fundamental factor controlling the interaction between surface water and groundwater and is an important parameter to quantify for addressing both water quality and quantity questions.  Riverbed Kv was investigated at four sites along the Great Miami River in southwest Ohio.  The sites comprised sediments ranging from clay to cobbles. Differently-scaled methods were applied including three types of seepage meters, slug tests, laboratory permeameter tests, and modeling of heat flow between the river and aquifer. Estimated riverbed Kv values were then compared to stratigraphic information from electrical-resistivity surveys and other geophysical methods applied by the US Geological Survey.  The various methods yielded widely different values for the same sites.  Among the methods applied, conventional seepage metering, slug tests and heat-flow modeling were found to provide the most reasonable values of riverbed Kv and provide reasonable agreement.  Riverbed Kv was lowest at a site of induced infiltration with a colmation layer consisting of a coarse sediment matrix clogged with finer sediment.  Heat-flow simulations, for example, yielded values from 0.073 to 0.26 m/d at this site.  Results from the three best methods were compared to electrical resistivity results. For three of the sites, there was good agreement between resistivity and Kv with low resistivities corresponding to finer sediment and lower Kv, and higher resistivity corresponding to coarser sediment and higher Kv. At the clogged site, however, resistivity was high and yet Kv was very low. Other geophysical methods were less reliable.  The discrepancies suggests that geophysical methods cannot be used alone as a method to determine the appropriate ranges of riverbed Kv especially at sites of induced infiltration where clogging is most likely to occur.