In September, a major lake near Kunming was heavily polluted with arsenic, leading to several cases of poisoning. In one of China's worst cases of river pollution , potentially cancer-causing chemicals, including benzene, spilt into the Songhua River in November According to Chinese history, the Yellow River Huang He has flooded 1, times in last 3,, years, while its main course changed 18 times and created some of the highest death tolls in Chinese history. The great river picks up and carries a large amount of yellow silt, dissolved in the water.
When the Huang flows onto the North China Plain, it changes from a swift river to a sluggish one. A It constantly raises the bed of the rivers.
Explanation: Loess is for the most part made by wind and glaciers. Loess frequently gathers in stream headwaters, and thusly gets conveyed to riverbeds. The development can be dense to the point, that it occupies the water over the nearby flood plain. The floods were primarily caused by poor management of the rivers, which were overwhelmed by extreme weather in These floods also reawakened the dream of building a massive hydroelectric power plant called Three Gorges Dam over the Yangtze River.
The Yellow River is the most important water resource for the dry north of China, playing an irreplaceable role in economic development, and agriculture. Since over 14 dams have been constructed on the river for hydroelectric power, which is vital to northern China's infrastructure.
Changes in the course of the lower Yellow River in historical times. The Yellow River flood of had a far more sinister and tragic cause: it was purposeful. In an attempt to halt invading Japanese forces, the Nationalist government in central China opened the dikes along the river.
The ensuing flood destroyed thousands of small villages and drowned an estimated , people. Heavy rainfall unleashed an enormous flood wave, which swelled further as dams burst, inundating more than 15, square kilometers. Disease epidemics broke out in the affected areas: in addition to the deaths caused directly by flooding, nearly as many lives were lost due to the ensuing sickness. The Huang He or Yellow River is the second largest river in China after the Yangtze and has a total length of 5, km.
The upper drainage basin originates in Ordos Basin and flows through numerous fold belts before reaching the Bohai Gulf. From its source, the river first flows east through deep gorges onto the Ordos Desert and finally through a relatively young valley in deposits of loamy soil known as loess. In this portion of its course, the river picks up and carries in suspension yellow silt, which colors the water.
The drainage basin has an area of , sq km and the tributary density is extremely dense, 0. The average elevation in the basin is 1, m with maximum elevations reaching 4, m. Rainfall is relatively low, the average annual rainfall being only mm a year, with a maximum and minimum of mm and 6 mm respectively.
The rainy months are May through September and the dry months are December through March when less than 25 mm of rainfall occurs. Most of the drainage basin is semi-desert or steppe grasslands. The alluvial valley is well-defined in the lower part of the drainage basin and is heavily populated.
What has changed over the past years is the number of people effected by these natural upheavals. After a disastrous flood in , the U. Army Corps of Engineers was charged with task of taming the mighty Mississippi. In building the longest system of levees in the world, the Corps successfully minimized flooding and improved the river's navigability. This dramatic achievement spurred millions of Americans to move onto the floodplain, where the soil was fertile and the property was cheap.
As a result, much of the river's bordering wetlands have been lost to agriculture and construction. Today, the Mississippi is outfitted with 29 locks and dams, hundreds of runoff canals, and miles and miles of levees. Most years, the system works remarkably well, but the flood of washed away the illusion of complete control. Most federal levees held, saving lives and land—but sent torrents of water towards less protected field and towns.
The '93 flood rekindled an old debate: what to do about the loss of the river's natural floodplain. Originally, the waters of the Mississippi spread over many thousand square miles of lowlands. Unlike cultivated farmland, wetlands possess a sponge-like quality that absorbs excess water in times of flooding.
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