Africa’s rivers face dramatic disruption(中断)that will leave a quarter of the continent severely short of water by the end of the century, according to a global warming study publish today.
The study, which appears in the journal Science Today, is the first to identify how Africa’s rivers will respond to climate change over the century. The extent to which slight changes in rainfall could impact on rivers had never been realized before.
The researchers used a computer to divide the continent into 1’000 km wide squares ( about 620 miles ) and worked out the total length of streams and rivers in each block. They used climate change models to calculate the expected changes in rainfall across the continent and the effect they would have on river levels. The scientists found that in 75%of the countries that receive between 400 mm and 1,000 mm of rain a year, shifts in rainfall caused larger rises or falls in river levers, than expected. In Harare a 10% drop in rainfall over Johannesburg and Bloemfontein will lead to a 70% drop in river levers.
The study predicts that rain will increase over east Africa. Climate change is expected to bring 10% more rain to Tanzania before the end of the century, increasing water course levers by 136%, while Somalia faces a 20$ rise in rainfall, leading to more than a 1,000% increase in the water it receives from waterways. However, increased rainfall could lead to more standing water, more mosquitoes, and widespread malaria.

　　根据今天发表的一份全球变暖问题研究报告，非洲的河流正面临严重的断流问题，到本世纪末，这将使非洲大陆四分之一的土地严重缺水。

　　发表于《今日科学》杂志上的这篇研究报告，首次明确提出非洲的河流将如何受到世纪之交气候变化的影响。降水的微小变化究竟会对河流产生多大程度的影响，这一点此前从未被人们意识到。

　　研究者运用电脑将非洲大陆划分成一个个边长1000公里（约620英里）的方块，并计算出每个方块区域中溪水与河流的总长度。他们运用气候变化程序模型以计算可以预见到的整个大陆的降水变化，以及这一变化对河流水位的可能影响。科学家们发现，非洲年均降水介于400毫米至1000毫米的国家中，有75%的河流水位会因降水变化而受到影响，水位涨跌的幅度要大于原先的预期。在哈拉雷，如果约翰内斯堡和布隆方丹降水减少10%，那里的河流水位将降低70%。

　　这项研究预测东非的降水会增加。气候变化预计将在本世纪末之前为坦桑尼亚多带来10%的降水，使那里的流域水位上涨136%，而索马里的降水将增加20%，从而使其流域水量增加1000%。然而，增加的降水也会导致更多的死水塘，产生更多的蚊子，使虐疾大范围流行。