流域

river basin / valley / drainage area

to flow / to disseminate / to circulate or spread / to move or drift / to degenerate / to banish or send into exile / stream of water or sth resembling one / class, rate or grade

field / region / area / domain (taxonomy)

Mesopotamia

Murray-Darling river system in the southeast of Australia

Changjiang or Yangtze river basin

the Yellow River basin