A tracer test for evaluating the heterogeneity of a shallow groundwater aquifer in the Tatun Volcano Group, Taiwan

Two multi-well tracer tests were conducted on two sides of a creek in Tatun Volcano Group, Taiwan to investigate the regional groundwater flow and to examine the heterogeneity of the region with conservative tracers. The sulfonic acids were used due to their reasonably good thermal stability and easily be analyzed by high-performance liquid chromatography (HPLC) using uv-absorbance detection.  Two breakthrough curves with multi-peaks were received and used to understand the existence of a hydraulic connection between injection and production wells but also used to gather crucial information about aquifer properties by using analytical models.  An analytical model, multi-fractures mode, was particularly used in matching tracer return curves.  Results show the existence of a dominated advection through a couple of fast flow paths/fractures between injection and receiving wells for one set while the other pairs have strong dispersion accompanied by the advection flow.