Comparison of aquifer parameters inferred from water level changes induced by slug test, earth tide and earthquake – A case study in the three Gorges area

Abstract

Hydraulic conductivity plays an important role in groundwater systems, but the estimation of hydraulic conductivity has many difficulties (the costs, feasibility and the scale-dependent results). In this study, we compared the hydraulic conductivity inferred from the conventional method (slug test) and the natural perturbation methods (tidal response and post-seismic water level recovery methods) at two confined wells, DJP well and MP well. The results show that the hydraulic conductivities estimated by the conventional method and the natural perturbation methods deviate somewhat from each other. The reason for the difference in hydraulic conductivities inferred from three methods is the variations of wellbore skin. By analyzing the uncertainty of estimation, we conclude that the different assumptions of the models cause inherent uncertainty and that the parameter uncertainty is secondary. The calculation results of these methods represent the different scales of the aquifer properties: 5–10 m for the slug test and 10–25 m for the tidal response and the post-seismic water level recovery methods, averaged by the hydraulic properties of the fault zone. The calculation errors of the three methods are 25% for the slug test, less than 10% for the tidal analysis and larger than 10% for the third method. Based on these comparisons, we conclude that the tidal response method is the most favorable way to infer aquifer parameters in this study. Both the tidal response and post-seismic water level recovery method provide a way to estimate aquifer properties as well as the mechanism of the co-seismic water level responses.