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Water Disasters

 (1) Flood

Caused by overwhelming or fierce rainfall (rainstorms or heavy rains), flood causes disasters of dyke breaching, mountain torrents, farmland flooding, building destruction and casualties. In China, flood is a frequent disaster with high intensity. The main flooded areas in China are the middle and lower reaches of the Yangtze River, Huang-Huai-Hai Plain, the lower reaches of Liao River, and southern China. In the past 30 years, the most serious flood occurred in Zhumadian, Henan province, which lasted from August 5 to 7 in 1975, with the highest precipitation of 1,605mm in three days (the average annual rainfall of this area was 800mm). Rainstorms triggered mountain torrents, breached the dykes of two reservoirs, flooded 11.3 thousand km2 of farmland, destroyed 100km of Beijing-Guangzhou Railway, killed tens of thousands of people, resulting in over 10 billion yuan direct economic loss.

 
(2) Drought
 Drought is a meteorological disaster caused by an extended period of continuous sunshine, high temperature, and consistently below average or zero precipitation. At its early phase, it’s difficult for people to sense its danger. In China, drought occurs throughout the year with spring drought, the most frequent type, in most areas of China, which is characterized by intense and persistent. The occurrence of drought is characteristic of relative concentration on time sequential. For example, among the 170 times of droughts, 115 droughts occurred in successive years from 1470 to 1947. Droughts also burst collective occurrence in space. For example, most parts of Inner Mongolia, Hexi Corridor in Gansu, north of Hebei and Shaanxi Province all encountered spring drought in 1950. And basins of the Yangtze River, Yellow River and Han River usually encounter droughts from July to September, altogether 11 times from 1950 to 1980.  
 
(3) Landslide
Landslide is a disaster with mass rocks and soil sliding along certain surface as a whole under the driving force of gravity, causing destruction to farmland, buildings and casualties along the slope. China is a mountainous country with frequent earthquakes and rainstorms which lead to frequent landslides. With the development of construction, landslides occur constantly in reservoirs, mines, cuttings, and mountainous cities. On August 25, 1933, the earthquake occurred in Diexi Town, Mao Wen County, Sichuan Province, caused the slumping of mountains within 15km around. The dashing of Diexi Town and Longchi Mountains resulted in the blocking of the Wo Jiang, forming a weir with a height of 160m. After 45 days, the water in the weir poured out over its dyke and exerted great damage to nearby areas of hundreds of kilometers.
 
(4) Mudslide
Mudslides often burst out in rainy seasons with thunders in valley with sediments and stones in torrents pouring down, and devastate everything on its way. Mudslides cover 23 provinces, municipalities and autonomous regions in China, and endanger all sorts of facilities of mining industry, transportation, farmland, water conservancy, etc. in mountainous districts. At about 22 o’clock on August 7, 2010, torrential rain poured into Zhouqu County, the Gannan Tibetan Autonomous State prompted an avalanche of debris flow from Luojiayu and Sanyanyu in the north of its county, which crashed down from north to south on the county seat, ripping and tearing many houses along the riversides. A barrier lake was formed as the Bailong River was intercepted by the mudslide. According to the news released by China’s Zhouqu Rescue Headquarters, the 8·8 catastrophic mudslide in Zhouqu killed 1,463 people, leaving 302 missing and a total group of 2,244 outpatients.    
 
(5) Water Eutrophication
Eutrophication is the phenomenon that algae and plankton reproduce extremely rapid with excessive nutritious substances like nitrogen and phosphorus poured into slow-running waters such as lakes, rivers, and gulfs. Algae limit the sunlight available to bottom-dwelling organisms which would die from the cease of photosynthesis and then rot and generate nutrients of nitrogen and phosphorus to be further absorbed by algae. For years, this vicious circle helps to fasten the reproduction of algae, worsen the water condition, make it smelly, reduce the amount of dissolved oxygen, and consequently suffocate fishes. Under the condition of eutrophication, the color of waters would be blue, red, brown, and milky due to mass reproduction of plankton. This phenomenon is called “water bloom” in rivers and lakes and “red tides” in seas for rapid reproduction of plankton turns sea water color into red. The plankton is smelly and poisonous which is inedible to fishes.
 
On May 29, 2007, a sudden water crisis swept through Wuxi, Jiangsu Province, and the chief culprit was the blooming of Cyanobacteria in Taihu Lake. Later, the blooming of Cyanobacteria broke out successively in Tien Lake and Chaohu Lake. On July 12, the State Environmental Protection Administration announced that China would set down stricter environmental standards in the watersheds of Taihu Lake, Chaohu Lake and Tien Lake, carry out a “High-Limit Penalty” measure to illegal polluters and further expand the range of “Limited Approval on Regional New Projects to Locality Pollution Prevention”.