A friend tried to describe it to me a year or so back, but his description didn’t make sense to me. When I saw the “hydraulic ram pump” for sale in the Lehman’s catalog it got my attention.
I’d call it a “reverberatory ram pump” but regardless; it is fascinating. You can google it yourself, or look it up on youtube. In short; it uses a larger flow volume by setting up a resonance to create pressure spikes that lift a smaller flow volume– No power input required beyond that of the kinetic & potential energy in flowing/falling water.
The design and construction is so simple that it could have been done in ancient Roman times. Though I have yet to look up its history, I’m guessing it’s development is much more recent than that.
There are other ways to skin that particular cat depending on the circumstances, but this one wins in the cool factor. What I also find interesting is the small scale on which some of these run. One of them on youtube shows a system running on little more than a trickle.