100 Places To Remember: Columbia River USA
Geschreven op 25-5-2010 - Erik van Erne. Geplaatst in Natuur
The Amazing Full Circle of Life. Forming much of the border between the states of Oregon and Washington, the Columbia River is the largest river flowing into the Pacific Ocean from North America in terms of volume.
For more than 15,000 years, Native American groups have occupied the territories along the Columbia River and its tributaries, their livelihood based mainly on fishing from the bountiful river. Today, the river is fished more intensely, and sustains large commercial fishing activities as well as subsistence fishing.
The river is home to several species of salmon, which are typically anadromous. Born in the fresh water of the Columbia River, the salmon migrate to the Pacific Ocean before, at the end of their life cycle, swimming hundreds of miles upstream against strong currents to return to the river system and spawn. Pacific salmon only make this amazing journey up-river once, and die shortly after spawning.
The heavy flow of the Columbia River the average flow at its mouth moves at around 7,500 cubic metres per second combined with its large drop in elevation, endow the river with enormous potential for electricity generation. However, the construction of a large number of dams in the Columbia River system is preventing salmon from reaching their spawning grounds. The dams also slow the current, so young salmon now take several months to make their journey downstream to the ocean, rather than two to three weeks.
The salmon stock in the Columbia River system has declined significantly in recent decades. Global warming will exacerbate the situation. Higher water temperatures will accelerate the development of salmon eggs leading to a smaller average size of juvenile fish, making them an easy target for predators and lowering the overall survival rate. By 2090, the habitat suitable for the salmon is expected to decrease by more than 40% in Oregon and Idaho.
