spilling water when flooding is a next big problem when generating hydropower dams.30/5/1989, heavy rain history has put down to the town of Johnstown, Pennsylvania. The reservoir behind the dam in danger of overflowing the banks. heavy rains during 24 h and the water rises to the top of the dam.No longer any place to go, the water spilling over the dam, the dam broke, water 80 m high wall collapsed and spill into the Valley Jonhstown.
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