underdrainage

例句：

1. 1. The underground drainage system is designed to remove excess water from the area.
   地下排水系统设计用来从该地区去除多余的水。
2. 2. The rainwater infiltrates into the ground and eventually percolates through the soil.
   雨水渗入地面，最终渗透过土壤。
3. 3.The subsurface water was slowly undersiding and causing the landslide.
   地下水慢慢下渗，导致了滑坡。