Determination of Variations in Streambed Conductance along Paint Creek through Riverbank Filtration – An Indirect Modeling Approach
2011
Nemecek, Matthew G.
Streambed conductance per area values range from 3.9 x 10-2/hr to 1.25/hr for Paint Creek, a river with an average daily discharge of 26.3 m^3/s and a drainage area of 2,090 km^2 in South-central Ohio. The several orders of magnitude change in streambed conductance is correlated with the time elapsed since a significant discharge event. Conductance values were determined from the response of groundwater levels in a state observation well about 105 m away from a USGS stream gage. The gage and adjacent observation well are in an area where Paint Creek valley is 2.14 km wide and floored with more than 23 m of coarse glacial outwash forming an extensive and heavily utilized aquifer system. Determination of realistic streambed conductance values for such alluvial aquifer systems, the sole source of water for much of southern Ohio, is critical, because with increasing water demand channel infiltration to adjacent public water supplies has increased while travel times between rivers and wells have decreased. Because the channel conductance determines the path and velocity of water traveling from the rivers to wells, accurate values are essential for calibrating models to assess the impact of surface water quality on groundwater. Streambed conductance per area values were determined by calibrating the groundwater model outputs to observed conditions. This method has several advantages over direct measurement with field instruments and laboratory determined channel sediment granulometry: the conductance values are representative over a large area of the channel, and they can be determined during flood peaks when streambed conductance per area is difficult or impossible to measure directly.
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