|
Home>News Center>China | |
|
|
|
|
|
|
|
|
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
Cloud seeding helps alleviate drought Addressing water shortages "The widespread use of this technology in northern China reflects the seriousness of the water shortage problem in this part of the country," Hu said. The average annual rainfall in China's arid north is only 65 per cent of the world average, while per capita water resources in the region are only about 40 per cent of the world average. One study reveals that northern China is hit by drought in 28 out of every 30 years, 11 of which see drought of severe proportions. "The growth in population and the development of the economy has led to a high increase in demand for water. This, combined with severe drought, has led to water shortages, a fall in ground water levels and the frequent drying up of rivers, including the Yellow River," Hu said. Meteorological officials said cloud seeding efforts to enhance rainfall are being used in drought-stricken northern China every time clouds amass. Years of drought in North China have even sparked reports that some towns were complaining of other towns stealing their rain by seeding clouds as they passed. "So co-operation in such cases is essential, and may require issuance of legislation regulating the legal aspects of cloud seeding," Hu said. According to the CMA, China has already issued regulations on clouding seeding to promote co-operation between provinces and regions. But up to now, only Beijing and Hebei Province have co-operated in carrying out cloud-seeding operations financed by the Beijing municipal government, which they have done twice since last year, according to a source in the Beijing Office of Artificial Weather Inducement. Expensive or not? The seeding process requires the use of a weather radar system and an aircraft equipped with instruments for meteorological recording and seeding operation or artillery to fire the silver iodide shells. Qualified radar technicians, engineers, meteorologists and pilots are also necessary. Cloud-seeding technology is generally considered an expensive process, so it can only be continued as a regular practice if it is efficient and effective. However, Hu Zhijin, a cloud expert with the China Academy of Meteorological Sciences, says that "cloud seeding is cheaper than other methods that the government is implementing to solve the water shortage problem, such as the South-North Water Diversion project that will carry water from the Yangtze River basin to Beijing and the North." "In one dry season only 2-3 million yuan (US$24,180 to 36,27) was needed to carry out the cloud seeding programmes," Hu said. In short, one cubic metre of man-made rain costs 0.2 yuan (2 US cents), according to the statistics provided by Zhang Qiang. Immature technology Because cloud seeding is an "immature" technology, as Hu says, it has also generated a certain amount of debate. Some people are afraid that large-scale seeding operations might have produced and continue to produce environmental problems. Hu reassured China Daily that so far there is no evidence to prove that chemical cloud seeding causes environmental pollution. "Because silver iodide is very effective, one gram of it can produce 100,000 billion ice crystals over a very wide area, so the quantity of silver iodine used is relatively tiny," Hu said. And nitrogen and calcium chloride, contained in cloud seeding materials, exist naturally in the air. Materials used for cloud seeding include silver iodide (in the form of Pyrotechnic), azotic cooling liquid, dry ice (CO2) and propane. Scattering the material from above the cloud produces better results than
doing it from below. Seeding is typically done using either aircraft or ground
generators, with the goal of facilitating optimal distribution of the seeding
material among the cloud components containing the largest portion of
supercooled water.
|
|
|
|
|
||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||
