泾渭分明

jīng wèi fēn míng

as rivers Jing and Wei separate clearly (idiom)

to be entirely different

jīng

Jing River

wèi

the Wei River in Shaanxi through the Guanzhong Plain 關中平原|关中平原[Guan1 zhong1 Ping2 yuan2]

fēn

to divide; to separate

míng

bright