Spatial variability of streambed vertical hydraulic conductivity and its relation to distinctive stream morphologies in the Beiluo River, Shaanxi Province, China

Abstract

Streambed vertical hydraulic conductivity (K v) is a key parameter in the analysis of interactions between streams and aquifers, and of stream ecosystems. However, knowledge of the streambed hydraulic conductivity associated with different stream morphologies is relatively scarce. An in-situ standpipe permeameter test method was used to determine the spatial variability in streambed K v measured along 18.5 km of stream reach in the Beiluo River, Shaanxi Province, China. The 59 total measurements were conducted at four test sites in three different stream morphologies: straight channel, anabranching channels and a nearby meander bend. There was great spatial variability in K v among the four test sites and three K v distribution patterns can be determined: (1) higher K v values appear on the erosional bank in contrast to lower K v values on the depositional bank at the two sites near meander bends; (2) the K v distribution in straight channels shows that the higher K v values occur in the center of the channel; (3) the K v values are generally highest on the branch with more alluvial forms in the anabranching channels. Moreover, grain-size analysis results illustrate that the average grain-size distributions of streambed sediments are significantly different on each side of the channel. The erosional and depositional forms are one of the driving dynamics for the distribution of streambed grain size that trigger the differences in the distribution of the K v.