渴了要饮水，脏了要用水洗，这是人类也是许多动物的本能。正因为人离不开水．天天与水打交道，所以，水成了人类最早被认识和利用的一种最重要的自然资源。我们在《人类最早的交通运扩工具》一文中已说过，古人在几万年前创造了木排，在一万年前创造了独木舟，又利用水的流动 Thirsty to drink water, dirty to be washed, this is human instinct of many animals. Because people can not do without water. Water deals with water every day, therefore, water has become one of the most important natural resources human beings have been first recognized and utilized. As we have said in the article “The earliest human transportation tool for mankind,” the ancients created wooden rafts tens of thousands of years ago, created canoes 10,000 years ago and exploited the flow of water