What are the benefits and downsides of coal?

Cheapest energy source, worst emissions

What are the benefits and downsides of natural gas

Less CO2 emissions than coal, but fracking leads to groundwater pollution

What are the benefits and downsides of nuclear energy?

Massive energy output, radioactive waste

What are the benefits and downsides of wind energy?

Clean energy, location specific and intermittent

What are the benefits and downsides of hydroelectric energy? How can the downsides be circumvented?

Consistent and reliable energy, prevents fish migration (can be prevented with fish ladders)