out·fall /ˈaʊtˌfɔl/
  河口,排水口
  Out·fall n.
  1. The mouth of a river; the lower end of a water course; the open end of a drain, culvert, etc., where the discharge occurs.
  2. A quarrel; a falling out. [Prov. Eng.]
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  outfall
       n : the outlet of a river or drain or other source of water