With the decreasing labefaction of our environment, the useable fresh water is facing pollution and becoming exhausted in the large-scale, and shortage is a threat to the whole world as well. 但是，当今随着人类生态环境的日益恶化，世界可用淡水资源正在逐渐枯竭并普遍受到人为污染，全世界正面临着可用淡水资源短缺的威胁。
