Abstract:

Hydraulic conductivity (K) is a fundamental hydraulic property for characterizing groundwater flow. However, studies on the variation of K in riparian shallow aquifers at different scales are rare. This study focuses on the loose sandy unconfined aquifer of the Luanhe River Estuary. We used three methodologies, including laboratory permeability test, slug test, and analytical inversion, to calculate effective K at the core, well-bore, and field scales. The findings reveal a clear trend of increasing K with scales, with the median K values of 0.71 m/d, 12.31 m/d, and 191 m/d at the corresponding scales, respectively. At smaller scales, the measured K captures the local heterogeneity of the aquifer. As the scale increases, more preferential flow paths are included, leading to a remarkable increase in K. At the large scale, the parameter reflects the homogenized characteristics of the aquifer system as a whole. The significant differences in K across scales highlight the importance of selecting scale-appropriate values tailored to specific engineering requirements and research objectives when studying groundwater-related processes, such as groundwater movement in unconfined aquifers affected by seawater intrusion and surface water-groundwater exchange. Moreover, this study provides essential data for the development and utilization of the aquifer in the Luanhe River Estuary, offering valuable methodological references for understanding water movement within aquifers in other regions.

Key words: hydraulic conductivity, scale effect, sandy unconfined aquifer