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.
2
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.
3
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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