Effects of hyporheic processes on streambed vertical hydraulic conductivity in three rivers of Nebraska

Streambed hydraulic conductivity is of great importance in the analysis of stream-aquifer interactions and stream ecosystems. We investigated streambed vertical hydraulic conductivity (K-v) with two connected depths in three rivers of Nebraska. Our results demonstrated that streambed K-v in the upper sediment layer was much higher than that in the sediment of the lower layer. We speculate that hyporheic processes can result in larger streambed K-v in the upper layer. 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 the sediments and further enlarge pore spaces in the upper layers. Also, permeability can increase as a result of expanded pore spaces caused by invertebrate activities in the upper part of streambed. The higher K-v will likely enhance exchange processes between stream and sediments.