wa·ter·course /ˈwɔtɚ/
  水道,河道
  Wa·ter·course n. Shipbuilding One of the holes in floor or other plates to permit water to flow through.
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  watercourse
       n 1: natural or artificial channel through which water flows
       2: a natural body of running water flowing on or under the
          earth [syn: stream]
       3: a conduit through which water flows [syn: waterway]