Water table response to rainfall and groundwater simulation using physics-based numerical model: WASH123D

Study region: Four districts (Meinong, Qishan, Dashu, and Daliao) of Kaohsiung city, Southern Taiwan Study focus: The understanding of aquifer recharge in terms of water table response to rainfall is of critical importance to groundwater systems management and various endeavors have been made to estimate the amount of recharge using rainfall data. The purpose of this study is to evaluate the groundwater level response to rainfall and determine the recharge potential for shallow aquifers. We showed a simple approach to estimate specific yield (S_y) and hydraulic conductivity (k) as functions of rainfall and water level data. New hydrological insights for the region: Correlation method is applied to investigate groundwater level response to associated rainfall and it was found that the rise in water table linearly depends on the rainfall amount per event. Results show the annual recharge rates of 244–1472 mm year^─1, which represent 12–43% of rainfall in the study area. The estimated k (order of 10^─4 to 10^─5 m s^─1) and S_y (0.20–0.51) were used as prior values to setup groundwater numerical modeling using WASH123D. The real-time case scenario simulation using pumping and rainfall data indicated the reasonable hydrological response of groundwater levels to rainfall. The long-term simulations should be performed with WASH123D to deal with the subjectivity of sustained groundwater pumping and sustainability of aquifers for better groundwater resource planning and management.