降雨首先因重力作用進入非飽和層，然後沿著孔隙向下滲漏抵達淺層非受壓飽和層，使其地下水位上升。在此過程中，水的移動受非飽和層材料透水性影響。多數區域都可以觀察到降雨與地下水位變化的直接關係，在桃園市龍潭區研究也發現，降雨對當地地下水位提升有立即的反應。然而在桃園市內其他地區的非飽和層普遍存在紅土礫石層，該地質材料主要由未膠結的礫石組成，並夾雜砂質或粉砂質的凸鏡體。其質地緻密且透水性差，形成雨水入滲的阻礙，影響降雨入滲的地下水補注過程，與其它區的反應明顯不同。因此，本研究旨在使用THMC軟體，建立多個二維模型，並且設定不同水力傳導係數與降雨模式，分析不同的降雨模式以及有無低滲透率地質材料覆蓋的情況下對降雨補注的影響。研究結果顯示當一透水均質材料在降雨入滲時，降雨量所造成的壓力變化呈現線性，而水力傳導係數造成知壓力水頭變化呈現非線性。此外，高強度降雨不代表可以在短時間內達成高效率的地下水補注，以及在低滲透材料的阻擋下明顯造成補注困難。;Precipitation first enters the unsaturated zone due to the force of gravity and then infiltrates downwards through the pores to reach the shallow unconfined saturated zone, causing the groundwater level to rise. The infiltration process is strongly influenced by the permeability of the unsaturated materials. In most regions, a direct correlation between rainfall events and groundwater level responses can be observed. For example, in Longtan District of Taoyuan City, rainfall induces a prompt rise in groundwater levels. However, in other parts of Taoyuan, the presence of lateritic gravel—composed of unconsolidated gravel mixed with sandy or silty lenses—creates a dense, low-permeability barrier that impedes infiltration, resulting in markedly different recharge behaviors. Therefore, this study aims to use THMC software to construct multiple two-dimensional scenarios with varying hydraulic conductivities and rainfall patterns to analyze the impact of low-permeability layers on groundwater recharge. Results indicate that under homogeneous permeable conditions, pressure head changes respond linearly to rainfall amount, whereas variations in hydraulic conductivity produce nonlinear pressure responses. Additionally, high-intensity rainfall does not necessarily result in efficient short-term recharge, and the presence of low-permeability materials significantly hampers the infiltration process.
