There was a time – especially in the 19th and 20th centuries – when nothing seemed to make more sense to community planners than to dam up their local rivers. Because rivers flow constantly, they seemed to provide an endless source of energy. That energy was first tapped to power mills, but later, dams of all sizes were built to convert that flowing power into electricity.
Dams were also the technology that people turned to to control floods and manage water supplies. By collecting river water and then releasing it on demand, it was possible to reduce flooding during storms or in the spring, when people living in mountainous regions had to contend with snow melt that would send rivers overflowing their banks.
But dams have had several significant downsides. For one, they make it difficult for fish like salmon and steelhead trout to reach their spawning grounds. Salmon famously swim upstream to spawn. But when they encounter dams that block their paths, their spawning runs come to a halt. Wildlife biologists have tried to build fish ladders to allow the animals to bypass the dam. Or, they trap the salmon and move them above the dam to continue their journey. Both approaches are expensive and have had mixed results.
Speaking of expense, many dams are so aged that the cost to repair them has become exorbitant. As other renewable energy sources like wind and solar gain ground, and as energy conservation gets increasingly more effective at reducing power demands, dams look less and less appealing.
Dams also flood scenic areas that often teem with wild animals and plants, or canyons notable for their archeological artifacts.
Finally, an unanticipated impact of building dams has been the effect they often have on the river’s ecology. Behind the dam, the water reservoirs intended to provide drinking water or a place for boating and swimming often have become silted up with mud, sand and gravel. Below the dam, the river beds are sorely lacking in these same materials, becoming little more than a muddy wasteland.
Dismantling a dam can take many forms. Some communities opt to literally blow theirs up. Others take a slower approach and unbuild a dam piece by piece or section by section. However it is done, by and large, scientists seem to be pleased with the results. Though the movement to remove dams is still relatively recent, research shows that native fish populations are bouncing back pretty quickly once a river is restored. So are the river beds and banks.
The moral of the story may be: Mother Nature knows best!