The heterogeneity of 3-D vertical hydraulic conductivity in a streambed

The heterogeneity of vertical hydraulic conductivity (K-v) is a key attribute of streambed for researchers investigating surface water-groundwater interaction. However, few three-dimensional (3-D) K-v models with high spatial resolutions have been achieved. In this study, in-situ permeameter tests were conducted to obtain K-v values. A 3-D model with 443 K-v values was built comprising 10 lines, 10 rows, and five layers. Statistical analysis was done to reveal the spatial characteristics of K-v. The influence of bedform on K-v values was restricted to the near-surface streambed. K-v increased with the increasing distance from the south river bank for the upmost layer, but it was not the case for other layers and the combined K-v values of five layers; the spatial pattern at transects across the channel did not differ significantly. The K-v values of each layer pertained to different populations; the sediments of individual layers were formed under different sedimentation environments. The coupling of erosion/deposition process and transport of fine materials primarily contributed to a reduction of the mean and median of K-v values and an increase of heterogeneity of K-v values with depth. Thus, a collection of K-v values obtained from different layers should be considered when characterizing the heterogeneity of streambed.