暗渠[ankyo] subterranean drain
渠魁[kyokai] ringleader
溝渠[koukyo] ditch
出渠[shukkyo] leaving the (repair) dock
入渠[nyuukyo] entering a dock

函渠[kankyo] drain with an oblong cross-section
乾船渠[kansenkyo] dry dock
船渠[senkyo] dock
暗渠排水[ankyohaisui] underdrainage
合流渠[gouryuukyo] combined sewer