A Systematic Comparison of Multiple Models for Depth-Dependent Decay of Hydraulic Conductivity in Salt Lake Areas: A Case Study of Typical Boreholes in the Qaidam Basin.

Hydraulic conductivity is an important hydrogeological parameter that characterizes the hydraulic properties of subsurface media, and the pattern of its variation with depth is of great significance for groundwater system simulation and resource evaluation. However, the applicability of some existing theoretical and empirical models describing how hydraulic conductivity varies with depth in salt lake areas still lacks systematic validation and evaluation based on measured data. In this study, seven typical boreholes in the West Taijinar Lake area of the Qaidam Basin were selected as the study objects. Several previous representative models describing the decay of hydraulic conductivity with depth, together with a newly proposed model using the geometric square root method, were selected for comparative analysis. The applicability of these models in a salt lake depositional environment was evaluated using the coefficient of determination (R2) and root mean square error (RMSE). The results show that hydraulic conductivity in the study area generally exhibits a significant decreasing trend with depth. Different models for the decay of hydraulic conductivity with depth show different levels of applicability among the boreholes in the study area, and each model can reflect the variation characteristics of hydraulic conductivity with depth to a certain extent. Among them, the model using the geometric square root method shows the strongest applicability for all types of boreholes, although it requires the largest number of parameters. The model of Zhang et al. (2026) and the model of Kuang and Jiao (2014) rank next, and both can better describe the characteristic pattern of hydraulic conductivity in the complex salt lake depositional environment, with rapid decline in shallow layers and gradually slower change in deeper layers. The results of this study can provide a reference for the characterization of hydrogeological parameters and groundwater flow simulation in salt lake areas and also provide a scientific basis for the evaluation of deep brine resources in the Qaidam Basin.