Let it Flow – The Case for Dam Removal

by | Aug 15, 2012

The damming of streams and rivers has its roots in early human civilization. From the earliest settlements, humans have diverted and stored water for a variety of uses. Today, there are more than 85,000 dams in the United States, serving a variety of functions, including flood prevention, water diversion and recreation. Dams play a significant role in the nation’s water supply and many large urban areas are supplied with water blocked by dams. Hydroelectric power from dams provides approximately 7 percent of electricity in the United States. About two-thirds of all dams are privately owned, and state and local governments own most of the remainder.

Although in the past dams were viewed as being almost entirely beneficial, today’s view of dams is more balanced, recognizing both the positive and negative effects.  Impounding and diverting water for upstream users modifies local habitats, affects plants and animals, and influences the lives of those who live downstream.  Dams can also present safety and economic risks due to the possibility of dam failure.  While the risks associated with aging dams are typically of low probability, the consequences are high.  Although dam failures are infrequent, the risk of failure increases with the age of the dam.

The first half of the twentieth century was the heyday of dam construction in the United States, peaking in the 1960s and decreasing significantly in the second half of the twentieth century and beginning of the twenty-first.  This means that America’s dams are aging.  The average age of a dam in the United States is more than 50 years old, and a small but significant number are a century old or more.  Many older dams no longer function as originally intended.  The dam structures may be in a state of disrepair, or the reservoirs created by the dams may have naturally filled in with sediment.

Currently, tens of thousands of dams are aging beyond their expected lifespans, with the possibility of attendant safety, environmental, and other problems.  Managing aging dams is quickly becoming a principal focus of dam engineering, made more challenging by the fact that existing dams represent different generations of design standards and construction practices.

Nationally, the number of high-risk dams is increasing.  In its Report Card for America’s Infrastructure, the American Society of Civil Engineers gave the nation’s dams a D grade.  It would cost an estimated $16 billion to repair the country’s most critical dams, and additional funding is needed for inspections and enforcement of safety programs.  Lack of funding for dam repair is a significant problem, particularly for privately owned dams.  The responsibility for dam upkeep and repair lies largely with the owners, many of whom cannot afford the costs.  Obtaining funding assistance, whether through government or private sources, can be difficult.

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