Sandra Postel: While dams serve very important purposes for human beings and our societies – controlling floods , drinking water, hydroelectric power – they are hard on the environment.
Sandra Postel is a former Pew scholar and prolific speaker and author on fresh water issues. Postel said there were 5,000 large dams in the world in 1950, while today there are 45,000. She said what we all know – that dams aid humans, but alter natural ecosystems. In this century, she said, it should be possible to implement technologies and that balance human and natural needs around large dams.
Sandra Postel: The idea is to ask, can we develop new rules for how we manage these dams and reservoirs so that they serve not only the traditional functions, but also benefit the ecosystem itself? And if we begin asking that, river by river, dam by dam, I think we’ll get some important benefits back to the ecosystem.
Postel said the flow pattern of water around dams is often key.
Sandra Postel: With bigger dams the question is really, can we to some degree mimic the natural pattern of flows that those rivers exhibited before those dams were built? It’s very much a current technological challenge.
She added that some dams have been experimenting with small floods – mimicking natural, large ones – in an attempt to boost the health of freshwater life.
Postel gave an example of the Glen Canyon Dam, on the Colorado River in the U.S. In May of 2009, a federal court struck down the dam’s approved operating plan, because the flow schedules were harming fish in Grand Canyon National Park. Supporters of the existing operations had said these flows were providing essential services to people nearby.
A federal judge ruled in favor of Grand Canyon Trust in its case against the U.S. Bureau of Reclamation, which runs Glen Canyon Dam. The legal decision can be found here.
Postel also talked about the flow of the Missouri River in the U.S, before it was dammed.
Sandra Postel : There would be a huge flood flow in the late spring, and that was the signal for the palette sturgeon to move upstream to spawn. Later on in the year, you’d have very low flows which established nesting grounds for river birds.
Thanks to Rick Moore of the Grand Canyon Trust in Arizona for his contribution to this story.
Our thanks to Sandra Postel.
Sandra Postel – a 1995 Pew Scholar in Conservation and the Environment – is founder and director of the independent Global Water Policy Project in Los Lunas, New Mexico. She is a prolific writer and speaker on fresh water issues. During 2000-2008, she was visiting senior lecturer in Environmental Studies at Mount Holyoke College, and from 2007 to 2008 she directed the college’s Center for the Environment. In 2002, she was named one of the “Scientific American 50” by Scientific American magazine, an award recognizing contributions to science and technology.
Photo Credit: Glen Canyon Dam and Bridge in Arizona by mandj98
Beth Lebwohl researches, writes and helps produce science content in audio and video formats for EarthSky. She is one of the authors on EarthSky.org, a script-writer for our podcasts, and helps host our English science podcasts in 90-second, 8-minute and 22-minute formats. Beth came to EarthSky in 2006 from the American Museum of Natural History's Department of Astrophysics, where she was surrounded by some of the greatest telescope-building, equation-wielding, code-writing physicists of our time. And they made her think . . . this science thing . . . it's pretty cool.