每日雅思词汇：孕育生命的河流　　激流turbulent river/treacherous rapids; 　　小溪creek/brook/stream; 　　水流flow/current; 　　干流main stream; 　　支流tributary/branch; 　　上游upper reaches/upstream; 　　下游lower reaches/downstream; 　　汇合处confluence; 　　堤坝dam/dyke/levee; 　　疏浚河道dredge a channel; 　　运河canal