Time goes as fast as water flows.
Time runs as easy as water downflows.
The stream of time emerges like water flows downstream.
楼主也可考虑以下的说法:-
Symbolically, a river represents the flow of time - It symbolizes the natural flow of water which flows from high mountain to low ground.
希望能帮到楼主!:)
Years as easily as water flows.
The years water equally is likely easy to the lower reaches