noun
aquifer
Geological term for an underground layer of water-bearing permeable rock or unconsolidated materials.
この地域の帯水層は、飲料水の重要な供給源です。
The aquifer in this region is an important source of drinking water.
Compound of 帯水 (taisui, 'water-bearing') + 層 (sō, 'layer, stratum'). The exact historical derivation is uncertain; the spelling is conventionally associated with the geological meaning.