在1948年至2004年间，位于美国西北部地区的哥伦比亚河的流量减少了约14%，这主要是由于降水量减少以及美国西部用水量增加。
The Columbia River in the us Northwest lost about 14 percent of its volume from 1948 to 2004, largely because of reduced precipitation and higher water usage in the west.
增加了的降水量超过排水系统的负荷。过去10年间，暴雨常引发下水道溢流。
Sewer systems weren't built to handle all that water. The last 10 years have seen more severe storms causing sewer overflows.
左图为1971-2000年间最大连续降水量、降水持续天数及雨止日期。具体数据见下表。
The figure indicates the maximum continuous precipitations, rain-lasting days and stopping dates in years from 1971 to 2000. For detailed data, see the table below.
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