Exploring Hydrogeological Reciprocity: A Case Study in Temporal and Spatial Variability

Past research on the hydrogeological parameters of the local aquifer has rarely utilized sequential pumping test (SPT) drawdown data collected from multiple tests at the same experimental site to comprehensively characterize the distribution fields of transmissivity (𝑇) and storage coefficient (S), as well as their reciprocity. To address this gap, this study aims to collect sequential SPT drawdown data from an experimental site located at the northeast corner of the well field at Yunlin University of Science and Technology, Douliu City, Yunlin County. The dataset spans five pumping tests conducted in 2010, 2012, 2013, 2018, and 2021, providing a unique opportunity to examine the spatiotemporal characteristics of these hydrogeological parameters.

The study first analyzes the reciprocity of drawdown levels observed at the same monitoring well under varying conditions across the five tests, uncovering the influence of temporal and spatial factors on hydrogeological behavior. Subsequently, the drawdown data is integrated into a hydraulic tomography (HT) numerical approach using the VSAFT2 model—a two-dimensional simulation tool for variably saturated flow and transport based on the modified method of characteristics. Through this method, the distribution fields of 𝑇 and 𝑆 are reconstructed for each case. Finally, the study conducts an in-depth comparison of the distribution fields of 𝑇 and 𝑆 across the five years, exploring their temporal evolution, spatial variability, and reciprocity. This research seeks to provide a clearer understanding of the dynamic characteristics of hydrogeological parameters over time and space, laying a solid foundation for further studies and practical applications in the field.