Effect of temperature on streambed vertical hydraulic conductivity

摘要

In this study, in situ and on-site permeameter tests were conducted in Clear Creek, Nebraska, USA to evaluate the effect of water temperature on streambed vertical hydraulic conductivity K_v. Fifty-two sediment cores were tested. Five of them were transferred to the laboratory for a series of experiments to evaluate the effect of water temperature on K_v. Compared with in situ tests, 42 out of the 52 tests have higher K_v values for on-site tests. The distribution of water temperature at the approximately 50 cm depth of streambed along the sand bar was investigated in the field. These temperatures had values in the range 14-19 ℃ with an average of 16 ℃ and had an increasing trend along the stream flow. On average, K_v values of the streambed sediments in the laboratory tests increase by 1.8% per 1 ℃ increase in water temperature. The coarser sandy sediments show a greater increase extent of the K_v value per 1 ℃ increase in water temperature. However, there is no distinct increasing trend of K_v value for sediment containing silt and clay layers.