8.10洪灾
章节大纲
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Is the water cycle perfect?
::水循环完美吗?The amount of water Earth has doesn't change. So if the water cycle were perfect, there would always be the right amount of water in each reservoir . In winter, there would be the right amount of snow . The snow would melt in the right amounts and at the right times in the spring. A good amount of rain would fall. Not so little that there would be a drought and not so much that there would be a flood . But the water cycle is not perfect. Floods are all too common.
::地球的水量没有变化。 因此, 如果水循环是完美的, 每个水库中都会有正确的水量。 在冬天, 将会有正确的积雪量。 积雪将会在正确的积水量中融化。 在春天, 积雪将会在正确的时段中融化。 大雨会降下。 降雨量不会太小, 干旱会少, 洪水也不会多。 但是水循环并不完美。 洪水非常普遍 。Floods
::洪水洪水A flood occurs when so much water enters a stream or river that it overflows its banks. Flood waters from a river are pictured below ( Figure ).
::洪水发生时,河水进入河水或河水,河水溢出。 河水洪水分布在下图(图 ) 。Flooding in Indiana.
::印第安纳州洪水泛滥Floods are a natural part of the water cycle, but they can cause a lot of damage. Farms and homes may be lost, and people may die. In 1939, millions of people died in a flood in China. Although freshwater is needed to grow crops and just to live, too much freshwater in the same place at once can be deadly.
::洪水是水循环的自然部分,但是它们会造成巨大的破坏。 农场和房屋可能会丧失,人们可能会死亡。 1939年,中国有数百万人死于洪水。 尽管种植作物和生活需要淡水,但同时在同一地点过多的淡水可能致命。Causes of Floods
::洪水原因Floods may occur when deep snow melts quickly in the spring. More often, floods are due to heavy rainfall. Floods happen when rain falls more quickly than water can be absorbed into the ground or carried away by rivers or streams.
::当大雪在春天迅速融化时,可能会发生洪水。 更常见的情况是,洪水是由暴雨造成的。 洪水发生时,雨水的降水速度要快于水被吸收到地面或被河流或溪流带走的速度。 洪水的降水速度要快于雨水被河流或溪流冲走的速度。Extremely heavy rains across the Midwestern U.S. in April 2011 led to flooding of the rivers in the Mississippi River basin in May 2011 ( Figure and Figure ).
::2011年4月,美国中西部大雨肆虐,导致密西西比河流域河流于2011年5月发生洪水(图和图)。This map shows the accumulated rainfall across the U.S. in the days from April 22 to April 29, 2011.
::本地图显示2011年4月22日至4月29日期间全美降雨量累积情况。Record flow in the Ohio and Mississippi Rivers has to go somewhere. Normal spring river levels are shown in 2010. The flooded region in the image from May 3, 2011 is the New Madrid Floodway, where overflow water is meant to go. 2011 is the first time since 1927 that this floodway was used.
::俄亥俄河和密西西比河有创纪录的流量必须到某个地方去。 2010年的正常春季河水位显示于2010年。 2011年5月3日的图中,洪涝地区是新马德里洪流大道,溢出水的目的地是那里。 2011年是自1927年以来首次使用该洪流道。Buffers to Flooding
::洪水的缓冲Heavily vegetated lands are less likely to experience flooding. Plants slow down water as it runs over the land, giving it time to enter the ground. If the ground is too wet to absorb more water, plants still slow the water’s passage. Slower water keeps all the water from entering the stream at once. Wetlands play a key role in minimizing the impacts of floods. Wetlands act as a buffer between land and high water levels. Flooding is often more severe in areas that have been recently logged.
::重植被土地不太可能遭受洪水。 植物在陆地上流水时减缓水速,给其进入地面的时间。 如果地面太湿,无法吸收更多的水,植物仍然会减缓水的通过。 较慢的水使所有水无法立即进入水流。 湿地在尽量减少洪水影响方面起着关键作用。 湿地是陆地和高水位之间的缓冲。 在最近登入的地区,洪水往往更为严重。Flood Protection
::防洪防洪保护People protect areas that might flood with dams. In dire situations, they use sandbags ( Figure ). Dams are usually very effective, but high water levels sometimes cause a dam to break. In that case, flooding can be catastrophic. Flood waters can also overflow a dam. People may line a river bank with levees to protect against floods. These are high walls that keep the stream within its banks during floods. Flood protection in one sometimes causes problems elsewhere. For example, a levee in one location may just force the high water upstream or downstream. This will lead to flooding in a different location. Sometimes water gets so high that the river must be allowed to flood.
::人们会保护可能会被水坝淹没的地区。 在恶劣的情况下,他们使用沙袋(图 ) 。 水坝通常非常有效, 但高水位有时会导致水坝破裂。 在这种情况下, 洪水也可能是灾难性的。 洪水也会淹没大坝。 洪水还可能淹没大坝。 人们可能会在河岸上划上高堤防洪。 这些是高墙,在洪水发生时将河水留在河水中。 洪水保护有时会在别处造成问题。 例如, 某个地点的堤流可能只是迫使高水位上游或下游。 这将导致不同地点的洪水。 有时水位太高,以至于必须允许河水淹。Sandbags are put out to try to keep floodwaters from overtaking a town.
::沙袋被放出 试图防止洪水 超过一个城镇。Effects of Floods
::洪水的影响Within the floodplain of the Nile, soils are fertile enough for productive agriculture. Beyond this, infertile desert soils prevent viable farming.
::在尼罗河的洪泛平原内,土壤肥沃,足以进行生产性农业。 除此之外,贫瘠的沙漠土壤阻止了可行的耕作。Amazingly, floods can be good. Flood waters carry nutrients that are deposited on the floodplain . So floodplains are good places for farming. In the past, the Nile River ( Figure ) in Egypt flooded each year . The flood waters brought much-needed nutrients in to farms. In the 1960s Egypt built the Aswan Dam to protects crop and settlements from the floods. However, after the dam was built, farmers began to need fertilizers to feed their crops.
::令人惊讶的是,洪水可能是好的。洪水水中含有沉积在洪泛平原上的养分。因此洪泛平原是很好的耕种地。过去埃及的尼罗河(图)每年淹水。洪水给农场带来了急需的养分。1960年代,埃及建造了阿斯旺大坝以保护作物和定居点免受洪水的侵袭。然而,在大坝建成后,农民开始需要肥料来养活作物。Summary
::摘要- Too much water in a drainage will result in a flood.
::排水系统太多的水会导致洪水。
- Floods are made worse when vegetation is cleared, when the land is already soaked, or when hillsides have been logged.
::当植被被清除、土地已经湿透或山坡被砍伐时,洪水就更加严重。
- People build dams and levees to protect from flooding. In an emergency, sandbags can be put out.
::人们建造水坝和堤坝来防止洪水。 在紧急情况下,沙袋可以扑灭。
- Floods are a source of nutrients on a floodplain.
::洪水是洪泛区养分的来源。
Review
::回顾- What is a flood?
::什么是洪水?
- What conditions make it more likely that a river will flood?
::是什么条件使得河流更可能淹水?
- What was the role of flooding on the Nile River? What was the consequence of damming the river?
::尼罗河洪水的作用是什么?
- Why are there floods on rivers that have dams and other protections?
::为什么在有水坝和其他保护的河流上发生洪水?
- Too much water in a drainage will result in a flood.
