noun
permeable layer; pervious layer
Geological term for a subsurface layer that allows water to pass through, such as sand or gravel.
この地域の透水層は地下水の重要な供給源です。
The permeable layer in this area is an important source of groundwater.
不透水層 is an impermeable layer that blocks water flow, the opposite of 透水層.
Compound of 透水 (water permeation) and 層 (layer).