KLAMATH, Calif.  — California’s second-largest river has sustained Native American tribes with plentiful salmon for millennia, provided upstream farmers with irrigation water for generations and served as a haven for retirees who built dream homes along its banks.

With so many demands, the Klamath River has come to symbolize a larger struggle over the American West’s increasingly precious water resources, and who has claim to them.

Now, plans to demolish four hydroelectric dams on the Klamath’s lower reaches — the largest such demolition project in U.S. history — have placed those competing interests in stark relief. Tribes, farmers, homeowners and conservationists all have a stake in the dams’ fate.