It starts with water and stone. A gravel bed high up some cool, clear stream where life begins for salmon. Eggs become swimmers, and soon the young smolts - noting the taste of their home waters so they can find them later - head downriver for the Pacific, feeling the ancient, ageless pull of nature.
But then the current slows, the river warms in the slack water behind a man-made monolith. Predators begin taking their toll.
There are more than 200 dams throughout the Columbia River Basin, monuments to mankind's ingenuity and insistent push for electricity and commerce.
The one pictured here is on the north fork of the Clearwater River in Idaho, which flows into the Snake River and on out through the Columbia. Like the others, it has a mass and stolid strength to match the power of what native Americans called Nch'i-wana or ''Big River.'' Standing here, one feels and hears an intensity and force dominating the other senses as natural might contends with engineered muscle.
Woody Guthrie sang of the dams' glory in the 1940s. Hydroelectricity powered the aluminum factories which meant more airplanes which helped win the war. Tamed with concrete, an area the size of Western Europe draining its moisture into the mighty Columbia became an irrigated cornucopia feeding a region and the world.
Then people noticed that not as many salmon were coming back to continue the cycle after their two or three years out in the Pacific. The coho, the chinook, and the sockeye were dwindling, and some runs disappeared entirely.
Those who operate these blockades now divert some water to ''flush'' the small fish past the churning turbine blades along their trip downstream. Fish ladders help the adult salmon return to spawning beds. But none of it is enough, and the numbers continue to drop.
Bureaucrats and politicians try to figure out how to save the salmon without offending other river interests. The problem seems as impenetrable as concrete and steel.
These are awesome and, in their own way, beautiful testimonies to what we think of as progress. But they also remind us of the unintended consequences of manipulating nature.