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The Roman dam at Cornalvo in Spain has been in use for nearly two millennia. Credit: Wikipedia / CC BY-SA 2.0
The decision to build, remove or modify dams involves complex compromises, often accompanied by social and political conflicts. A group of researchers from the natural and social sciences, engineering, arts and humanities joined forces to show how, where and when it would be possible to achieve a more effective balance between these compromises. Their work is presented in an article published in the Proceedings of the National Academy of Sciences (PNAS).
What is the problem of the dam?
In some parts of the world, it is proposed to build thousands of new massive dams for hydropower, flood control and irrigation. In other regions, such as the United States, there is a growing trend towards river restoration by removing obsolete dams, posing security risks or having significant negative impacts on ecosystems. In both cases, difficult compromises and differing preferences of stakeholders can significantly complicate decision-making processes.
For example, conservation groups and resource agencies seeking to restore marine fish often favor the removal of dams preventing these species from reaching their spawning grounds. However, other stakeholders can appreciate the various services that dams can provide, including water supply, hydroelectricity and reservoir recreation.
"This is exactly the type of problem for which you need an interdisciplinary team with the right blend of expertise to quantify trade-offs and identify promising solutions from multiple perspectives," says lead author Sam Roy. from the University of Maine.
Maximize economic and ecological benefits
The research team has assembled a database of more than 7500 dams in New England as a "model system" to search for decisions that yield effective results for multiple criteria valued by stakeholders. These criteria include habitat availability for migratory fish, hydroelectric power generation, water storage, drinking water supply, water quality, recreation, risk of dam failure , impacts of shoreline properties and decision costs.
Using an economic concept known as the frontier of production possibilities, combined with a scenario-ranking technique, researchers have identified potential dam decisions that maximize the combined ecological and economic benefits for individual watersheds as well as for biodiversity. entire region of New England. Given the size of the database (the largest of its kind in the world) and the considerable number of potential solutions, an automatic learning approach was used to simulate the many compromises and find solutions to maximize the total benefits.
The team's approach can be used to identify many types of decisions that yield effective results given the resources and technological constraints, including those that remove or modify specific dams to produce the greatest increase in productivity. fish habitat through a slight reduction in hydroelectric energy or improved dam breccia for a small reduction in the supply of drinking water.
"We also find that it is possible to improve the tradeoffs between certain criteria by coordinating several dam decisions at larger spatial scales," said Roy. "This means that there are many opportunities to find win-win solutions that can both improve dam infrastructure, freshwater ecosystems and decision costs by removing, altering or modifying even by selectively constructing specific dams in a watershed. "
Interdisciplinary research that links points
Roy, Senator UMaine Senator George J. Mitchell's Center for Sustainability Solutions Postdoctoral Fellow, has worked with colleagues at the University of New Hampshire, the University of Rhode Island, and the Rhode Island School of Medicine. Design.
"One of the strengths of our interdisciplinary approach is that we can look at many trade-offs using an integrated and quantitative framework," said co-author Emi Uchida, environmental economist at I & # 39; 39, University of Rhode Island. The team also collaborates with various stakeholders (eg tribal communities, government agencies, conservation organizations) to strengthen the scientific basis of decision-making.
The authors cite the Penobscot River multi-stakeholder restoration project as a very successful example of coordinating the removal and alteration of dams through broad stakeholder engagement, significantly reducing conflict, allocating resources effectively and respecting pre-existing constraints on the ownership and regulation of dams.
"Our model can help identify specific decisions that will gain the support of a broad stakeholder audience by providing desirable tradeoffs in terms of infrastructure and ecosystems. This could encourage funders and practitioners to make these decisions a reality. number of future decisions that repeat the success of the Penobscot River restoration project. "
Explore further:
Study finds significant savings by removing dams instead of repairs
More information:
Samuel G. Roy et al., "A multi-scale approach to balance the trade-offs between dam infrastructure, water course restoration and costs" PNAS (2018). www.pnas.org/cgi/doi/10.1073/pnas.1807437115
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