Water is one of the most valuable resources in all over the world. Everyone seems to know that water is used in household, industrial, agricultural, recreational and invironment activities. But few people care about it takes millions of year to accumulate water. The world's supply of fresh water is decreasing while the world population is continuously rising. Moreover, the water's system advancement is not directly corelated to the geographical factors but the gorvenment's policies as well as the citizens' usage responsibily. Two typical cities which illustrate this idea are Jiangnan, China, a water-surrounded city and Las Vegas, USA, a desert-like place. Jiangnan City nurtures a large number of lakes, including the Yangtze River, the main river in the city. Yangtze River, the supply of drinking water for 186 cities along its bank, is in danger of pollution with more than 1,300 lakes dead. Just 31 percent of the water is of first or second class quality, with 35 percent under the third class. The expert even alerted that if the situation continued like this, more than 70% of Chinese people would have water of low quality, especially when China is facing the crisis of water shortage-300 million people and 3.2 million farm animals do not have drinkable water. Even though the government has proposed policies on water puritication, nothing has been effective to prevent the Yangtze river system from being destroyed. A dam has been built to eraducate water containmenation problem but this dam has unfortunately contributed to the damage of lakes and wetlands. Besides, the government also plan to release 5bn cubic metres of water for irrigation, drinking supplies and ecosystem support, etc... Until now, no deffinite plan has been carry out. With the ongoing process of industrialization and transformation, along with the citizens' disposal of garbage into the water, the river ecosystem is also endangered. The dolphin is one of the few kinds of mammals that can only live in freshwater. Since 1950s, the Yangtze river is the living environment of thousands of freshwater dolphins. But this population, engtangled and suffocated by the water pollution, was decreased to only 13 animals in 1999. According to the article "Yangtze river dolphin driven to extinction" by Ian Sample on Thegardian, "The Yangtze river dolphin, until recently one of the most endangered species on the planet, has been declared officially extinct following an intensive survey of its natural habitat. Incontrast to Jiangnan City of China, Las Vegas is a
