Are dams a futile business?

California is launching the biggest dam removal in state history, returning the Carmel River in Northern California to (nearly) its original free-flowing state.

While this is a victory for wildlife and the riparian ecosystem, the reason behind this dam removal isn't so altruistic. 100 years of silt, that would normally have been carried to the ocean, has built up behind the dam, rendering it virtually unusable. Furthermore, California's Division on Dam Safety has declared the dam "seismically unsafe," meaning the communities below would be at great risk for dam failure and flooding if an earth quake were to occur.

Dam on the Carmel River. Photo credit: http://ow.ly/mghsT

The US has 84,000 dams, many of which were built in the mid-20th century in a rat race between the Bureau of Reclamation and Army Corps of Engineers. Some dams were built to enable large-scale population growth in arid territory, yet disturbingly, many were built simply to build more dams. Undammed rivers became viewed as a "waste," and we lost sight of the ecological purpose of a free-flowing stream. 

More dangerously, we saw a duty to populate regions that without massive, expensive, and probably unsustainable water projects, could not support more than a dusty little town. Marc Reisner in his monumental book Cadillac Desert, a scathing history of American water projects, chronicles this phenomenon, and it is well worth a read.

Reisner predicted our dams would eventually silt up and lose functionality. While humans can divert and disrupt natural hydrography, and perform stunning feats of engineering, it can only last for so long. 

John Sabo, a water researcher at Arizona State University, and his team conducted a study to verify Resiner's claims from 1986, the year Cadillac Desert was published. Though Reisner based his theories on history and logic, rather than data, Sabo's study found the claims to be sound. Reisner, who died in 2000, was perhaps the most clairvoyant environmental historian in our time.

What we have failed to take into account is the duration for which man can outsmart nature. We can build pipelines and dams, and irrigate the desert, but we cannot violate the laws of the ecosystem. A river must continue to the sea.