Rivers are the bloodstream of a continent, ferrying the nutrients that keep it healthy and recycling its waste products into new sources of energy. We know that now. But for two centuries America dammed its rivers in the name of progress, nearly destroying nature’s brilliant scheme in a misguided effort to improve upon it. As a source of electrical power, dams are nearly obsolete, accounting for only 11 percent of our total usage. They decimate fish populations, obstruct piscine migration, and thus disrupt the food chain. They change water temperatures and degrade water quality in ways harmful to both vegetation and wildlife. They change soil quality and prevent nature’s flood control mechanisms–wetlands–from doing their job. They hold back the silt, gravel, and nutrients that make agriculture sustainable. They breed bacterial disease.

But dam removal creates almost as many human and technical problems as did putting the damn things up in the first place. Dams invited some people to populate deserts and pushed others off soon-to-be-flooded land. Dams created lakes that created tourism that created jobs. Dams shaped the history of entire states, notably California.

Grossman, a native New Yorker, became radicalized on the subject after moving to Oregon. There, she says, "rivers and salmon are with us as we walk to the corner," yet dams have rendered many species of salmon nearly extinct. For this book she also visited communities where river reclamation efforts are underway, with varying degrees of success, in Maine, North Carolina, Colorado, Arizona, Wisconsin, California, Montana, and Washington. So far, Wisconsin–an intensely watery place, with 40,000 miles of rivers, streams, lakes, ponds, and wetlands–has the best record of dam removal, largely because there is no shortage of water to begin with.

In dry states such as Colorado, Arizona, and California, by contrast, the antiremoval activists are holding the line. In California, where the grid of dams and water diversions reminds the author of a map of the New York City subway system, the politics of dam removal remain highly charged. California’s water consumption competes with the needs of native fish and river restoration, so much so that the state legislature recently declined to fund even a mere assessment of the state’s dams. At the same time, many of California’s small, privately owned dams have been so poorly maintained that their existence poses more of a threat than does their removal.

While the complexities of dam removal cannot be overstated, Grossman learns, neither can the conviction of environmentalists, politicians, and others concerned with civic planning that the time to act is now. "The longer we wait to remove dams that have outlived their usefulness," she concludes, "the more difficult the problems plaguing these rivers may become."

–A. J. Hewat