Assessment of spatial variability of hydraulic conductivity of seasonally frozen ground in Northeast China

Groundwater flow has an important impact on the hydrological properties and environmental prediction of seasonally frozen ground in Northeast China, and the hydraulic conductivity of warm frozen soil is the key factor. Due to the complex geology, environment and human activities, the hydraulic conductivity shows spatial variability. This study tests the saturated horizontal hydraulic conductivity (K-h) and saturated vertical hydraulic conductivity (K-v) of seasonally frozen ground in Southern Heilongjiang, Northwest Jilin and Northern Liaoning, Northeast China. The statistical characteristics and variability of K-h and K-v of warm frozen soil under three temperature (-0.1 degrees C, -0.3 degrees C and -0.5 degrees C) are obtained. Then the scale of fluctuation (SOF) of K-h and K-v of seasonally frozen ground are calculated by random field method. Five theoretical two-dimensional auto correlation functions (2-DACFs) are used to characterize the spatial variability of hydraulic conductivity. The autocorrelation distance (ACD) and ACF of hydraulic conductivity of seasonally frozen ground in Northeast China are assessed. The results show that the measured K-h and K-v of seasonally frozen ground are discrete. The lower the temperature is, the smaller the hydraulic conductivity is. The statistical characteristics of K-h and K-v are different when the cold temperature is the same. The fitting degree of the linear regression equation of the measured K-h and K-v is very good. The ACD of the K-h and K-v of seasonally frozen ground are different due to different 2-DACFs. The SOF and ACD of the K-h are larger than the SOF and ACD of the K-v. The ACF of hydraulic conductivity decreases with the increase of local average distance. This study clearly clarifies the spatial variability of hydraulic conductivity of seasonally frozen ground and the results can provide reasonable basic data for the random analysis of groundwater flow of seasonally frozen ground in Northeast China.