noun
underdrainage; subsurface drainage
Technical term used in civil engineering and agriculture for drainage systems installed below ground.
この農地では暗渠排水が整備されている。
Subsurface drainage is installed in this farmland.
排水 is general drainage; 暗渠排水 specifically refers to underground drainage systems.
Compound of 暗渠 (underground conduit) and 排水 (drainage).