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美国正面临着日益严重的干旱。它的东部地区一些地方发生了自从三十年代以来少见的干旱现象,而它的西部地区则存在着长期性的水源枯竭问题。美国每年平均降水量约为七百五十毫米,但是降水量极不均衡。在西经一百度(从北部的北达科他州到南部的得克萨斯州都在这一线上)以东的大部分地区,每年降水量为七百五十毫米至一千二百五十毫米。在西北太平洋区域每年降水量约为二千五百毫米,而西南太平洋地区却不到五百毫米,其中加利福尼亚州死谷
The United States is facing an increasingly serious drought. In some parts of its eastern region, a rare drought has occurred since the 1930s, while its western region has long-term water depletion problems. The average annual precipitation in the United States is about 750 millimeters, but the precipitation is extremely uneven. In most parts of the country, east of Baidu (from North Dakota in the north to Texas in the South), precipitation ranges from 750 millimeters to 1,250 millimeters annually. In the Pacific Northwest, precipitation is about 2,500 millimeters annually, less than 500 millimeters in the Southwest Pacific, including Death Valley, California