The energy required to operate and maintain the dam is often equal to the energy produced by the dam.

Dams often change the current and width of a watershed, altering the riparian ecosystem.

Many fish populations (including salmon and trout) are decimated because dams restrict access to essential habitat.

Dams can contribute to flooding and resulting property damage.

Animals that rely on fish as sustainance may begin to decline because the dam has permanently altered fish habitat.

Most if not all rivers capable of generating substantial hydroelectric energy have already been dammed and are working at high capacity.

The amount of energy invested in hydroelectric is about equal to the amount of energy harnessed from the process.

With the pressing issue of climate change and changes in precipitation, it is unclear how much energy current hydroelectric dams can provide in the future, let alone how much energy dams built in the future could provide.

There is currently a federal ban on the construction or development of future hydroelectric dams to protect fish populations.

The reported amount of electricity generated by hydroelectric dams is actually an inflated figure derived from theoretically running at full capacity and is not realistic.