An Investigation of Hydraulic Connections and Origin of Water at a Well Field Near Chien-Shih Area, Shinchu, Taiwan by Using Stable Isotopes and Hydrographs

Abstract

Estimates of groundwater recharge constitute the fundamental input to evaluate and manage groundwater resources. An environmental isotope and hydrogeochemical study was carried out to conceptualize the surface water and groundwater interaction, so as to explore the flow pattern of groundwater related with the geological setting at a well field near Chien-Shih area, Shinchu, NW Taiwan. This research established a monitoring network of groundwater levels among one pumping well and other four wells at NCU Research well field in the study area. The methodology utilized includes tracer techniques, field investigations and hydrological budgets. Data of boundary conditions, aquifer properties, groundwater levels, and groundwater production were incorporated. Conventional field hydrogeological study and hydro-records support the isotope and hydrochemical analysis. Hydrograph diagrams can further illustrate the fluctuation of local water tables affected by recharge from watershed in mountainous area. In addition, the isotopic data were compared with past geochemical characteristics of aquifer and local meteoric water line. Then, the observed stable isotopic characteristics of the samples can serve as valuable database for local water resources management. Therefore, the isotopic and hydrochemical data is essential in confirming possible mixing relationships among aquifers, whereas traditional hydraulic data is unable to provide the needed quantitative assessment. Finally, a conceptual model is presented and supported with Interactive Groundwater simulations in cope with data collected in the study area.