从总体上看,美国的农业用水资源是比较丰富的,因此在本世纪70年代以前,政府的政策主要倾向于对农业水资源的开发和利用;而在70年代后的20多年来,由于水资源污染严重而逐渐呈现出水资源短缺,因而,政府的政策倾向则明显地加大了水资源的保护力度。美国农牧业生产自身对农业水资源污染主要来自以下几个方面:一是普遍使用化学杀虫 Generally, the agricultural water resources in the United States are relatively abundant. Therefore, by the 1970s, government policies mainly focused on the development and utilization of agricultural water resources. In the 20 years after the 1970s, due to the fact that water The serious pollution of resources gradually shows the shortage of water resources. Therefore, the policy tendency of the government obviously increases the protection of water resources. Agriculture and animal husbandry in the United States of their own pollution of agricultural water resources mainly from the following aspects: First, the widespread use of chemical insecticide