Water damming is the procces of making a block to run water through a area, into the system, and then ran back out.  We do this, by looking at areas for water power system, testing water level, and speed of the water, to find a good point to set up a system. All we have is water turnning through a system, that turn internal gears, that produce power stored in generators, that can be later hooked up to make power. The water supply is not cut off because the water runs though the system, and is sent back out of the system, into the eco system again.