Is love like water?

"Love," begins the title story of Chapel Hill author Samia Serageldin's collection,

..."is like water." It took me a long time, and much grief, to understand what she meant.
    ...
    "Love," she would say, "is like water," meaning that love flows from the older to the younger, and not vice versa, just as water flows downhill and not up....[pp. 23, 26-27]

Could that be true? I've felt it flowing the other way, many times.