HR: 16:15h
AN: H24F-02    [Abstracts]
TI: Vertical variation of vertical hydraulic conductivity in channel sediments
AU: * Chen, X
EM: xchen2@unl.edu
AU: Song, J
EM: jsong3@unl.edu
AU: Cheng, C
EM: ccheng2@unl.edu
AU: Wang, D
EM: wangdeming@gmail.com
AU: Lackey, S
EM: slackey1@unl.edu
AU: Burbach, M
EM: mburbach@unl.edu
AB: Vertical hydraulic conductivity (Kv) of streambed is of great importance in the analysis of stream-aquifer interactions. We used two methods to estimate the Kv in three rivers of Nebraska. The first method was in-situ permeameter test in river channels. We investigated streambed vertical hydraulic conductivity (Kv) in two depths, one incumbent to the other, immediately beneath the channel surface. Our results demonstrated that streambed Kv in the upper sediment layer was much higher than that in the sediment just beneath the upper layer at each test location. We speculate that hyporheic processes can result in a larger streambed Kv in the upper part of channel sediments. Specifically, water exchange through upwelling and downwelling zones can lead to bigger pore spaces and a more unconsolidated structure of sediments in the upper layer. The upward movement of gas produced by redox processes can loosen sediments and further enlarge pore spaces in the upper layers. Bio- activity in the upper part of the streambed can also expand pore space and thus increase hydraulic conductivity. In-situ permeameter tests penetrated the sediment to depth as much as 90 cm. We then used Geoprobe direct- push technique to generate electrical conductivity log and collect sequences of sediment cores from larger depths. Permeameter tests were conducted on these cores to determine Kv. Our results suggest that Kv values have a decrease tendency with the depth for sediments in these rivers.
DE: 1830 Groundwater/surface water interaction
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2007 Fall Meeting