There are a few Names for this device, the most well known:

Hydraulic Ram Pump
Gravity Pump
Water Flow Pump
River Flow Pump

This is the ultimate example of a Free Energy device!

A proven device that has worked since the 1700s, but not well known about to many.

When I was young lad, about 12, we lived on a farm. As farmers do, we had to improvise after a pump broke down. My Dad was handy with his hands and a few people he knew were also. After getting hold of some ideas on how the Hydraulic Ram Pump worked we got to work building this pump. Its an absolute ingenious device and so simple a kid could build it, which is what I did with help from my dad.

This device has no input except for the Rivers Flow, its a Gravity Pump.

Brief Description of the Device:

Water from the River starts flowing down the Drive Pipe. The flow of Water speeds up in time. As the flow of water gets to a certain speed, the Gate Valve shuts off automatically as a result of the water pressure. A one way valve is also present in the chamber. Water pressure in the chamber as the gate valve is forced to maximum and as a result the water forces the one way valve open, forcing water up the one way valve. The one way valve automatically shuts off when the water pressure drops below the threshold of the one way valve's spring. The water pressure drop also opens the gate valve and the Water starts to flow in the Drive pipe again. No input is needed at all, this device runs entirely on Gravity and water pressure created by Gravity.

Another good video here with a good description:

ref: http://www.omafra.gov.on.ca/english/crops/pub19/6moveh2o.htm