Research on hydrogeological parameter inversion of an aquitard based on multi-source data: A case study of a silt layer in the Hohhot Basin

An aquitard is an important part of an aquifer system. It is always difficult to determine the hydrogeological parameters of the aquitard. Traditional laboratory tests are difficult to overcome the influence of stress state and environmental change on the aquitard layer parameters. Therefore, evaluation of hydrogeological parameters under in-situ state is of great significance. This article selects a silt layer in the Hohhot Basin, and primarily designs and carries out pumping tests and solute transport tests. The unstructured grid with the controlled volume finite difference method is used to establish a 3D coupling model of groundwater flow and solute transport. Groundwater levels and concentration data are used to estimate the hydrogeological parameters of the aquitard. The results show that the variation in groundwater levels and solute concentrations in the pumping wells calculated by the model can fit well with the actual observation data, and the coefficient of permeability of the pumping aquifer identified by the model (4.8 m/d) is similar to the analytical result (4.17 m/d). The numerical model conforms to the actual hydrogeological conditions. The vertical hydraulic conductivity of the aquitard studied in this paper is 1.2×10⁻⁴ m/d, and the specific storage is 1.0×10⁻⁵ m⁻¹. The method presented in this paper may provide references for the parameter determination of an aquitard.