Variation of hydraulic conductivity with depth in the North China plain
The unique relationship between hydraulic conductivity (K) and depth (D) is hardly observed because K is affected by many geologic factors. To characterize the variation of K with D in unconsolidated sediments, 820 samples were collected from eight boreholes along the Hutuo River in the direction of flow in the North China Plain (NCP) The K values of these samples were determined using the geophysical logging and grain size data, after which the K series with D for eight boreholes were divided into three components: seasonal, trend, and random components, using the random forest (RF) and time series (TS) methods. The results indicate that the stratum pressure has significant effects on the variation of K with D in the upper layers for H2, H5, H6, and H7 and in the deep layer for H1, H3, and H4. It is here concluded that K can decrease with D when the effects of sedimentary environment and random errors are eliminated. The decreasing trend component of K includes three different decay models, and its difference value shows a decreasing trend from the piedmont region and central plain to the coastal area. The conclusions drawn in this paper are crucial to understanding the dependence of K on D in unconsolidated sediments, which can provide key information for quantifying deep groundwater flow and transport.
Arabian Journal of Geosciences