The water shortage has been a local issue from its springing up to now that governments are responsible for the supply and demand of water resources. According to the relevant survey, although the water resource is abundant in world, owing to the limited of fresh water, irregular distribution of water resource, increasing population, human ' s improper exploitation and utilization caused pollution,etc..the lack of fresh water resources has been a world problem.

The earth is truly the water planet. However, the resources can be used are extremely limited: only a percentage of all and the distribution of them are extremely uneven. Adequate water resources area will cause the phenomenon of waste water on account of without awareness of water conservation. The area with lack of water resources will also exhaustive exploit water resources to solve the problem and it will resulting the destruction of ecological environment and water pollution which can be affect water cycle, and finally, decrease the total fresh water resource. What is more, the growth of population is also one of the reason. I would talk these arguments in the following paragraphs.
1.water quantity and distribution
Earth is truly the water planet. Oceans cover 72% of surface, the water sphere contains an estimated 1.5 billion cubic meter. However, 97.3% is salt water. As result of the salt and other reasons, the brine is not be able to drinking, irrigation or even for industrial. The other three percent of