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Water is a human survival and development of irreplaceable resources , to understand overview of water resources , cherish and protect water resources, for the protection of human health and promote sustainable economic development is of great significance .
Many people mistakenly believe that water is inexhaustible , it is not. Although a lot of water on Earth , reaching 1.47 billion tons, accounting for 7% of the total Earth . However, they are mostly salt water , unfit for human consumption and the use that can really make life of fresh water and agricultural water use , accounting for only 2.8% of the total water . This is 2.8 per cent , there is a large part of the solid-state accumulation of snow and ice in polar and mountain , or on a gaseous drift due to natural evaporation in the atmosphere ; another part of it is buried deep in the ground is not easy to obtain groundwater ; another part of the absorbed by the growth of the consumption of wildlife , it can actually dominated by human water , accounting for only 0.56% of the total water is really pathetic !
Only 0.56% in the water , and because the natural distribution of the inhomogeneity, the land about 1/ 3 of the region a serious water shortage , and another 1/ 3 of the region is also insufficient water , only 1 /3 of the area is more water rich, but because of environmental pollution , water quality degradation , and some is not suitable for drinking and use, not only exacerbated the shortage of water supply situation , but in the wet areas , but also the gradual emergence of contaminated water shortage situation.
China's large population , shortage of freshwater resources per capita world average of 1/ 3 , with water pollution and uneven distribution , China has 45% of the land is classified as arid or semi- arid regions , more than 600 cities in the country , more than 200 more than a dozen different levels of water scarcity, many farmers often want to Northwestern few kilometers away boy, perennial water shortage problems. All seven major river systems and major lakes are subject to different degrees of pollution, and some have been quite serious , located in Jiangnan some towns , there have difficulty in drinking water , restricting the sustainable development of the economy . Guilin , although rainfall, abundant water , but due to the uneven distribution of rainfall season , the Lijiang River in the driest season average water flow is only 15 m 3 / s or so , historical minimum flow of 3.8 m 3 / sec. Several years of drought have happened Guilin water tight . Even if the water is very rich now , free to pay more not only their own waste water , but also increase the water plant construction investment ; becomes wastewater after use , they need to convey through the sewage pipe network to purify sewage treatment standards before released into the environment , otherwise it will cause rivers and groundwater pollution HUTANG ; while the construction of urban sewage treatment systems and sewage treatment facilities run year round , are the need to spend a lot of money, manpower and material resources , which would cause unnecessary consumption of resources . So From whatever perspective, cherish and protect water resources are necessary.