The picture you see above is the ThreeGorges Dam's massive turbines. It utilizes 32 generators, thirty 700MW units and two 50MW known as Francis turbines.

James B. Francis invented the design in 1848 and these turbines are reaction types, which means water loses is pressure and energy as its moves throught the turbine and drives the runner.

High pressure water enters through the spiral casing surrounding the guide vanes and the water flow towards the runner blades will spin at 75 revolutions per minute, driving a vertical shaft attached to an immense electromagnetic generator.

The main array of 700MW turbines each weigh approximately 6,000 tons and pass between 21,000–34,000 cubic feet of water every second. These turbines achieve an average efficiency—how much of the water's energy is converted into mechanical energy—of nearly 95 percent.

In the eight years, the dam has been even partially operational, it has produced over 500TWh of electricity.

[Power-Technology - Bright Hub - Francis Turbine Wiki - Three Gorges Dam Wiki]