众所周知，水在地球引力的作用下，总是从高处流向低处。但人类在改造自然、征服自然的斗争中，却发明了使水向高处流的提水工具。人们使用提水工具，最早是从井中取水开始的。方法是以瓮汲水，要想把瓮从井中提出，就得向上用力拉，这样不但费力而且效利区低。随着井灌的逐步 It is well known that water always flows from high places to low places under the gravitation of the earth. However, in the struggle to transform nature and conquer nature, human beings have invented the water lifting tools that make the water flow to a higher level. People use the lifting tool, the earliest is to start from the well water. Method is to urn water, in order to raise the urn from the well, you have to pull up, so not only laborious and low efficiency area. With well irrigation step by step