Hydraylic ram pump - "siphon" version
This pump is based on the "hydraylic ram" principle, so it's using water stream as a power source ("stream" meaning there must be continuous flow of water).Unlike typical hydraylic ram pump, this one is used for draining water from below ground/stream level (pit water etc.).
More about how it works
Video on Youtube
See also gold sluice banjo/highbanker with shaker idea.