国家地理 旱灾的成因与影响

Its signs are subtle and slow: the earth dries; water levels fall; the rains do not come; and the land is gripped by drought.

干旱的迹象很微小很缓慢：地面干燥；水位下降；雨季不到；土地龟裂。

At its most basic, a drought occurs when more water is used than is replenished¹.

最根本的原因是，当水量应用超过水量补给时，就会发生干旱。

It is a balance between supply and demand, with both natural and human factors in play.

供给和需求之间有一个平衡点，这要考虑自然和认为因素。

The weather is constantly in flux². A low pressure system allows moist air to rise, cool and form rain clouds.

天气是变幻无常的。低气压系统使潮湿的空气上升，冷凝，形成降雨云。

A high pressure system traps the air beneath it, and banishes³ the clouds.

高气压系统挤压下面的空气，将云消除。

Droughts form when changing wind patterns cause high pressure systems to last for months, or even years.

当变化的风向造成高气压系统持续数月甚至几年的时间时就会发生干旱。

Aggravating⁴ the problem is society's demand for water. Farms are heavily dependent on water to irrigate⁵ crops and provide pasture for livestock⁶.

社会对水的需求量使这个问题更加恶化。农田以来水来灌溉作物，为牲畜提供牧场。

Urban areas also place huge demands on available water supplies. If the demand can't be reduced, then the drought begins to take its toll⁷.

城市地区也对可用水供应有大量需求。如果需求两不能降低，干旱就会造成损失。

Crops eventually wither⁸ and die. Soil erodes⁹ away into clouds of dust. Forest fires spread rapidly.

庄稼最终枯萎，死亡。土壤变成灰尘流失。森林大火迅速蔓延。

The damage to the environment has large-scale consequences for us human population.

对环境造成的损害也对人类造成大规模的影响。

Short-term droughts cause stress on both the environment and people.

短期干旱对环境和人类都造成压力。

Long-term droughts can lead to war, famine, disease or mass migrations¹⁰.

长期的干旱可能会导致战争，饥荒，疾病和大规模的人口迁移。

In the 1930s, a severe drought in the Great Plains caused massive crop failures. In some places, the drought lasted 8 years.

上世纪30年代，大平原地区发生了严重的干旱，导致大面积作物歉收。在有些地区，干旱持续了长达八年时间。

So much soil blew away became known as the Dust Bowl.

土壤被风吹走，形成人所共知的沙尘暴。

Over 50 million acres of land were affected¹¹, forcing many farmers to abandon their own property.

5000多万英亩的土地受到影响，许多农民被迫遗弃他们的财产。

But by historical standards, the Dust Bowl was mild and short-lived. Some droughts have lasted for decades.

但是根据历史标准，沙尘暴不比较温和，持续时间比较短。有的干旱延续达几十年之久，

The famines they create have killed over 40 million people in the 20th century alone.

造成的饥荒仅仅在20世纪就使4000多万人丧命。

Like other forms of weather, droughts are one of the earth's natural processes. There is very little we can do to stop them.

像其他形式的天气一样，干旱是地球自然过程的一种。我们无法阻止他们。

The best we can do is prepare for when droughts do come before everything blows away.

我们能做到最好的就是当为干旱做好准备，以防一切都被吹走。

1 replenished   

补充( replenish的过去式和过去分词 )； 重新装满

参考例句：

• She replenished her wardrobe. 她添置了衣服。
• She has replenished a leather [fur] coat recently. 她最近添置了一件皮袄。

2 flux   

n.流动；不断的改变

参考例句：

• The market is in a constant state of flux.市场行情在不断变化。
• In most reactors,there is a significant flux of fast neutrons.在大部分反应堆中都有一定强度的快中子流。

3 banishes   

v.放逐，驱逐( banish的第三人称单数 )

参考例句：

• Work banishes those three great evils: boredom, vice, and poverty.(Voltaire, French philosopher) 工作撵跑三个魔鬼：无聊、堕落和贫穷。（法国哲学家伏尔基泰） 来自互联网
• The Consumer: It Banishes Uterine Fibroids, but for How Long? 消费者：它驱逐子宫的纤维瘤，但是为多久？ 来自互联网

4 aggravating   

adj.恼人的，讨厌的

参考例句：

• How aggravating to be interrupted! 被打扰，多令人生气呀！
• Diesel exhaust is particularly aggravating to many susceptible individuals. 许多体质敏感的人尤其反感柴油废气。

5 irrigate   

vt.灌溉，修水利，冲洗伤口，使潮湿

参考例句：

• The farmer dug several trenches to irrigate the rice fields.这个农民挖了好几条沟以灌溉稻田。
• They have built canals to irrigate the desert.他们建造成水渠以灌溉沙漠。

6 livestock   

n.家畜，牲畜

参考例句：

• Both men and livestock are flourishing.人畜两旺。
• The heavy rains and flooding killed scores of livestock.暴雨和大水淹死了许多牲口。

7 toll   

n.过路(桥)费；损失，伤亡人数；v.敲(钟)

参考例句：

• The hailstone took a heavy toll of the crops in our village last night.昨晚那场冰雹损坏了我们村的庄稼。
• The war took a heavy toll of human life.这次战争夺去了许多人的生命。

8 wither   

vt.使凋谢，使衰退，(用眼神气势等)使畏缩；vi.枯萎，衰退，消亡

参考例句：

• She grows as a flower does-she will wither without sun.她象鲜花一样成长--没有太阳就会凋谢。
• In autumn the leaves wither and fall off the trees.秋天，树叶枯萎并从树上落下来。

9 erodes   

侵蚀，腐蚀( erode的第三人称单数 )； 逐渐毁坏，削弱，损害

参考例句：

• The sea erodes the rock. 海水侵蚀岩石。
• The sea erodes the land. 海洋侵蚀陆地。

10 migrations   

n.迁移，移居( migration的名词复数 )

参考例句：

• It foundered during the turmoils accompanying the Great Migrations. 它在随着民族大迁徙而出现的混乱中崩溃。 来自辞典例句
• Birds also have built-in timepieces which send them off on fall and spring migrations. 鸟类也有天生的时间感应器指导它们秋春迁移。 来自互联网

11 affected   

adj.不自然的，假装的

参考例句：

• She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
• His manners are affected.他的态度不自然。