Beyond Dams: Options and Alternatives
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Rivers weave in and out of our lives, providing innumerable benefits to communities across the world. In the United States, we rely on our rivers for drinking water, irrigation, aquatic habitat, fisheries, energy, navigation, recreation and simply the natural beauty they bring to our landscapes. Humans have been building dams and other river blockages to harness and control water for centuries, attempting to secure its benefits for human use. Estimates put the number of dams in the United States anywhere between 76,000 to 2.5 million.
However, as society has come to understand, dams can cause significant social and environmental impacts that outweigh the benefits they provide.
By design, dams alter the natural flow regime, and with it virtually every aspect of a river ecosystem, including water quality, sediment transport and deposition, fish migrations and reproduction, and riparian and floodplain habitat and the organisms that rely on this habitat.
Dams also require ongoing maintenance. For example, reservoirs in sediment-laden streams lose storage capacity as silt accumulates in the reservoir. In arid climates reservoirs also experience a high rate of water loss to evaporation. Dams also can have significant economic impacts on dam owners, the surrounding community and society in general.5 As dams age, maintenance costs and safety hazards often increase, resulting in an increasing financial burden and liability on the dam owner. Depending on the river and the fisheries being impacted by the dam, an owner may also be required to retrofit the structure with fish passage facilities or make other upgrades to comply with water quality standards.
When dams diminish fisheries, communities can lose jobs and sustenance, or the source of their cultural or spiritual life. Because of these and other concerns, some dam owners and managers are finding that it makes more sense to remove certain dams, often benefiting the community ecologically and socially, rather than make costly repairs or upgrades. However, when such dams still provide valuable services, alternatives to replace the dams’ functions should be considered.
The purpose of this report is to provide stakeholders and decision-makers with an overview of low-impact and non-structural alternatives to dams. It is designed as a reference for anyone interested in exploring options for replacing a function served by an existing dam or replacing a function to be served by a proposed dam.