Uses of uranium dating

When a dam slices through this moving ecosystem, it slows and warms the water.In the reservoir behind the dam, lake creatures and plants start to replace the former riverine occupants.Yet only 3% of dams in the US are hydropower facilities—together supplying about just under 7% of U. “The West developed through the construction of dams because it allowed the control of water for development,” says Emily Stanley, a limnologist at the University of Wisconsin, Madison.But for most dams, none of these are their primary purpose.Mark Ogden, the project manager for the Association of State Dam Safety Officials, says many small private dams were indeed built for recreational activities like fishing.Grant, Magilligan, and Doyle have a different theory, however.Dams may get the recreational label, Doyle says, “when we have no idea what they are for now, and we can’t stitch together what they were for when they were built.” But while many of the original uses have disappeared, the dams have not.In the very center of conservationist hell, mused John Mc Phee, surrounded by chainsaws and bulldozers and stinking pools of DDT, stands a dam. “They take away the essence of what a river is,” Stanley says. A flowing river carries sediment and nutrients downstream and allows flora and fauna to move freely along its length.

“We as a nation have been building, on average, one dam per day since the signing of the Declaration of Independence,” explains Frank Magilligan, a professor of geography at Dartmouth College.Roughly 98% of the salmon population on the Elwha River disappeared after the dam went up, says Amy East, a research geologist at the U. Migratory shad, mussels, humpback chub, herring—the list goes on.He notes that the charismatic salmon are a more popular example than the “really butt-ugly fish we’ve got on the East Coast.” Dams not only upend ecosystems, they also erase portions of our culture and history.Now, demand for power in Las Vegas and Phoenix regulates the flow.“They turn the river on when people are awake and turn the river off when people go to sleep,” explains Jack Schmidt, a river geomorphologist at Utah State University.

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