China's longest river shorter than believed

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 ◆ China's longest river shorter than believed

Scientists have found that China's longest river, the Yangtze, is nearly 90 kilometers (56 miles) shorter than previously thought, Xinhua said recently.

A new measurement of the river using satellite technology found that it stretches for 6,211.3 kilometers (3,851 miles), shorter than the accepted length of 6,300 kilometers (3,906 miles).

But it is still the longest river in China and the third longest river in the world, according to Xinhua.

"It does not mean the river shortened," said Liu Shaochuang, a researcher with the Institute of Remote Sensing Application under the Chinese Academy of Sciences.

"This is the result of the improvement of measuring techniques and different starting and ending points," he said.

The new data has to be examined by the State Bureau of Surveying and Mapping before it can become official national geographic data.

Liu, who headed the survey, said the satellite remote sensing technology used to remeasure the river was far more accurate than the previous measuring method that relied on topographic maps.

Researchers measured the river in downstream and upstream directions three separate times using nearly 40 images taken by a US satellite.

The data was then calculated by computer.

The widely-accepted length of the Yangtze River comes from a survey conducted more than 20 years ago.

The measurement from the 1970s showed that the Yangtze is longer than the Mississippi River in the United States.

The longest river in the world is the Nile River in Africa followed by the Amazon River in South America.

The location of the main source of the Yangtze River has long been debated in academic circles because there are many headwaters, or tributaries in the upper reaches, said Shi Mingding, an expert of the Yangtze River Water Resources Committee under the Ministry of Water Resources.

In addition, the water course of the river at the estuary is so wide that it is difficult to determine where the river ends and the sea begins, Shi said.

More than 400 million people live along the Yangtze. The industrial and agricultural output value of the area accounts for 40 percent of the country's total.(chinadaily.com)