What are the costs of hydroelectric energy?

Hydroelectric power has been touted as the 'environmentally clean, renewable source of power.' This is subject to debate, as hydroelectric dams use turbines to generate electricity, and these turbines are spun by shafts which have blades on them. Fish which get caught in the high-pressure streams of water directed at the turbine blades usually do not survive the encounter with the blades. Also, the impoundments, or lakes, behind hydroelectric dams slow the speed of the river so much that many young fish do not survive the long swim to the ocean, where food is plentiful in comparison to rivers. Of course, dams present a complete barrior to upstream migration, unless fish ladders are in place, and even fish ladders are not 100 percent effective, as many fish are unable to locate the ladders. Salmon populations upstream of Grand Coulee Dam, which does not have fish ladders, disappeared, except for the freshwater varieties.