Refining the Characteristics of Hydrogeolgical Settings in Pingtung Plain of Taiwan

To improve the benefits of the groundwater resources management and utilization efficiency of Pingtung Plain located at Southern Taiwan, this study focused on the understanding of the hydrogeological settings and groundwater flow behavior of this area as well as assessing the reasonable of the delineation of  groundwater recharge geologically sensitive areas (GWRA) by various field investigation techniques.

Following the aforementioned purposes, totally four boreholes with the depth of 100 meters were drilled spreading around GWRA in 2019. According to the core logging analysis of Zaixing site located at the region of GWRA, we found that the gravel formation, distributed at shallow layer, was playing an important role of the benefit of groundwater recharge due to its hydraulic conductance. Furthermore, the Changxing, Silin and Huamin sites were located spreading around the boundary of the GWRA. The lithology of Huamin site was mainly composed of thick layers of gravel and mud, while Changxing and Silin sites were composed of thick layers of gravel and coarse sand, and thin layers (around 4 to 10 meters thickness) interspersed locally with three to four layers of gravel and coarse sand. The interlayer of fine grain sediments in this area showed that it is unfavorable for vertical infiltration of surface water and rainfall into deeper aquifers. To analyze the characteristics of aquifer and estimate hydrogeological parameters, the constant-rate pumping tests were conducted in two different sites located in GWRA. The hydraulic conductivity (K) and specific yield (Sy) of Zaixing site were 3.8×10^-3 m/sec and 0.16 respectively, while those of Silin were 1.6×10^-3 m/sec and 0.17. Finally, we could summarize that the Pingtung Plain had the relative higher conductance and capacity of water resources based on the comparison results of the range of hydraulic conductivity and specific yield with nine major groundwater area.

Therefore, an elaborate plan of hydrogeological investigation and assessment of groundwater resources of Pingtung Plain are very crucial to face the challenge of water scarcity in the near future.