A steam turbine essentially _does_ use the motion of the water.
In conventional hydroelectricity, gravity causes the motion through the energy differential of the waters' height.
In a steam turbine, the potential energy is from the high temperature of the water, and the energy input to rotate the turbine comes from the temperature differential of the steam cooling.
In theory you could capture the hydroelectric energy of the water on its way down a 12 mile hole, but that gravitic potential energy is negligable compared to the energy difference between superheated steam and water.
In conventional hydroelectricity, gravity causes the motion through the energy differential of the waters' height.
In a steam turbine, the potential energy is from the high temperature of the water, and the energy input to rotate the turbine comes from the temperature differential of the steam cooling.
In theory you could capture the hydroelectric energy of the water on its way down a 12 mile hole, but that gravitic potential energy is negligable compared to the energy difference between superheated steam and water.