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干旱的危害干旱的危害有哪些( 二 )

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Types of drought
Ship stranded by the retreat of the Aral Sea.As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases. People tend to define droughts in three main ways:[45]
Meteorological drought is brought about when there is a prolonged period with less than average precipitation. Meteorological drought usually precedes the other kinds of drought.
Agricultural droughts are droughts that affect crop production or the ecology of the range. This condition can also arise independently from any change in precipitation levels when soil conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops. However, in a traditional drought, it is caused by an extended period of below average precipitation.
Hydrological drought is brought about when the water reserves available in sources such as aquifers, lakes and reservoirs fall below the statistical average. Hydrological drought tends to show up more slowly because it involves stored water that is used but not replenished. Like an agricultural drought, this can be triggered by more than just a loss of rainfall. For instance, Kazakhstan was recently awarded a large amount of money by the World Bank to restore water that had been diverted to other nations from the Aral Sea under Soviet rule.[46] Similar circumstances also place their largest lake, Balkhash, at risk of completely drying out.[47]
The world is not only hungry, it is also thirsty. This may sound strange, since nearly seventy percent of the earth's surface is covered with water. But about ninety percent of this is sea water. Man and most of the animals can only drink and use the remaining percent of water--fresh water.
The need for water is increasing day by day. Only steps are taken to deal with this problem immediately can we avoid a severe world-wide water shortage later on. One of the first steps is to develop ways to reuse it.
Experiments have already keen carried out in this field.The used witer has been pumped to a water-purifying plant.There, it can be separated from waste matter and treated with chemicals so that it can be used again, just as if it were fresh water from a spring.
三：干旱的危害有哪些6条旱灾的危害包括以下几个方面：
（1）干旱的最直接危害是造成农作物减质、减产，农业歉收 。如：早稻高温逼熟造成空壳率增加，部分稻田出现了开裂、倒伏现象 。
旱地作物旱象更为明显，花生枯死，脐橙出现叶片发黄、卷曲等干旱症状 。
（2）在严重干旱时，人们饮水发生困难，生命受到威胁 。
【干旱的危害干旱的危害有哪些】（3）干旱将造成水利发电量减少，能源紧张，严重影响经济建设和人们生活 。
（4）在干旱季节，容易发生火灾，且难以控制和扑灭 。
大多数火灾，特别是大的森林火灾都发生在干旱季节 。
（5）旱灾还常常带来蝗灾的发生 。

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