美国灌溉现状分析

Present Situation of Irrigation in USA

以１９９７年的美国灌溉统计资料为基础，结合近２０多年的数据，本文详细分析了美国的农田灌溉在近２０多年的发展状况，并从地理位置、气候类型和灌溉规模等不同角度全面分析了美国各种灌溉方法的构成、灌溉所用动力类型和灌溉农田上的作物结构。结果显示，近２０多年来，美国总灌溉面积中喷灌所占比例在不断增加，而地面灌溉比例则不断降低。１９９７的资料显示，在目前美国的灌溉面积中，喷灌是以中心支轴式系统为主，微灌以地表滴灌为主，而地面灌中则有３种类型的系统使用的较多。在灌溉农田的作物结构上，干旱地区的饲草类作物种植比例明显高于其它地区，而湿润地区的粮食作物、瓜果蔬类作物和棉花的比例较高。

Based on 1997 Annual Irrigation Survey and Annual irrigation survey data in last 20 years, the development of irrigation in USA in last 20 years are analyzed in this paper. The constitution of various irrigation methods, the types of irrigation power units, the situation of irrigation wells and the crop constitution in irrigated land are also analyzed systematically on view points of geographical locations, climate features and total irrigation area. The results show that percentage of sprinkler irrigation has been increasing and the percentage of the surface irrigation has been decreasing gradually in last 20 years in USA. The analysis on 1997 annual irrigation survey points out that center pivot is the main system in sprinkler irrigation, surface drip/trickle is the main system in low flow irrigation, and three kinds of main system in surface irrigation are applied nearly equally. On the crop constitution in irrigated land, the proportions of the alfalfa and pasture hay crops are higher in arid and semi arid area, but the proportions of the grain crops, cotton and melons/fruits/vegetable crops are higher in humid area.