干旱地区需要灌溉才能使作物生长。
这些河流和河川系统被称作“外源河流”，因为它们的源头位于干旱地区之外。
These rivers and river systems are known as "exogenous" because their sources lie outside the arid zone.
这样的计划是非常必要的，因为在许多干旱地区，我们并不清楚其地下水资源的范围。
Such programs are much needed because in many arid lands there is only a vague idea of the extent of groundwater resources.
地下水通常聚集在河流流域，但在干旱地区，地下水也可能完全保留在干涸河床的表面之下。
Groundwater commonly collects in stream drainages but may remain entirely beneath the surface of dry stream-beds in arid regions.
另一方面，在干旱和半干旱地区，湖泊数量少，湖泊之间距离远，减少了相互关联的可能性。
In arid and semiarid regions, on the other hand, the small number of lakes and the great distances between them reduce the possibilities for correlation.
那片现在是沙漠的地区和所有干旱地区一样，对降雨量相对更大或更小的周期极为敏感，因此那里的动植物分布发生了巨大且迅速的变化。
The areas that are now desert were, like all arid regions, very susceptible to cycles of higher and lower levels of rainfall, resulting in major, sudden changes in distributions of plants and animals.
后来，他们学会了按季节耕作，适时播种，以及在干旱地区利用每年的洪水来灌溉他们的农田。
Later, they learned to work with the seasons, planting at the right time and, in dry areas, making use of annual floods to irrigate their fields.
一千年前，梯级井是印度最干旱地区的生活基础。
A millennium ago, step-wells were fundamental to life in the driest parts of India.
起源于干旱地区的流动性河流和溪流通常被称为“内源河流”。
Regularly flowing rivers and streams that originate within arid lands are known as "endogenous".
为了粮食和稻草，珍珠谷子是在非洲和亚洲最炎热、最干旱地区种植的谷物。
Pearl millet is a cereal grown for foodgrain and straw in the hottest, driest areas of Africa and Asia.
在半干旱地区，草地通常是最主要的天然植被，而该地区主要的经济活动是家畜饲养。
The raising of livestock is a major economic activity in semiarid lands, where grasses are generally the dominant type of natural vegetation.
美国国家环境总署和世界银行开始拨款并着手调查干旱地区的地下水资源，以开发合适的开采技术。
The United Nations Environment Programme and the World Bank have funded attempts to survey the groundwater resources of arid lands and to develop appropriate extraction techniques.
美国西南部半干旱地区的湖泊水位在上一个冰河时代似乎比现在更高，这一事实曾一度归因于降水增加。
The fact that lake levels in the semiarid southwestern United States appear to have been higher during the last ice age than they are now was at one time attributed to increased precipitation.
令人惊讶的是，干旱地区拥有着世界上最大的一些河流系统，如澳大利亚的墨累-达令河、北美的里奥格兰德河、亚洲的印度河和非洲的尼罗河。
Arid lands, surprisingly, contain some of the world's largest river systems, such as the Murray-Darling in Australia, the Rio Grande in North America, the Indus in Asia, and the Nile in Africa.
研究大沙鼠在中国干旱地区的分布。
这里是极端干旱地区，只有适者能够生存。
There are extreme arid regions where only the fittest survive.
随着气温升高，沙哈拉等干旱地区正从外缘开始逐渐变绿。
As temperatures rise, the Sahara and other dry areas are greening on the edges.
非洲干旱地区进程。
在干旱地区使用甜菜这样的农作物来制作燃料的行为必须抛弃掉。
Using crops like sugarbeet to make biofuels in dry regions must be abandoned.
一份之前发布的地表温度图，也显示了同期该干旱地区受到的极端高温。
A previously published image of land surface temperatures shows extreme heat in the drought region at the same time.
而从2002年到2008年，这一干旱地区的平均降水量只有50厘米每年。
And the arid region's rainfall levels were above the average of 50 centimeters per year from 2002 to 2008.
水荒在干旱地区的威胁日益严重，全球43个国家约7亿人面临水源紧张问题。
Water scarcity had become more of a threat in arid regions, and about 700m people in 43 countries were facing water shortages.
从土豆中榨取的水分能够取代自来水的供应，在一些干旱地区甚至能为人们提供饮用水。
Water extracted from potatoes could replace supplies from the tap and even provide drinking water in areas suffering from drought.
侯赛因及其同事长期的研究表明，大坝尤其使干旱或半干旱地区的极端降水模式发生改变。
The long-term studies by Hossain and his colleagues suggest that dams have particularly altered extreme precipitation patterns in arid or semiarid areas.
侯赛因及其同事长期的研究表明，大坝尤其使干旱或半干旱地区的极端降水模式发生改变。
The long-term studies by Hossain and his colleagues suggest that dams have particularly altered extreme precipitation patterns in arid or semiarid areas.
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