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全球大幅度变暖,使得水循环加快,蒸发和降水增强。长江中下游地区在20世纪90年代已呈现出明显增温趋势,达到0.2～0.8℃,最大增温区域在长江三角洲地区。降水在长江流域中下游地区增加明显,增加值为5%～20%。20世纪90年代是继50年代后,长江流域性洪水灾害高发的10年。长江流域是我国经济发展的核心地区,对长江流域725个县洪水灾害脆弱性分析结果表明,近1/3的地区是洪水灾害高脆弱性地区。按照1998年社会经济状况,若遭遇1954年型、1991年型、1996年型和1998年型的洪水时,洪水灾害造成的可能损失分别为589、55、70和196亿美元。气候模拟预测表明,21世纪长江流域地区的增温可能达到2.7℃,导致降水可能增加10%,径流可能增加37%。在全球变暖的趋势,以及区域社会经济可持续发展造成不透水面积增大和单位经济价值升高的共同影响下,长江流域发生相当于1870年、1954年和1998的千年、百年和20年一遇洪水的可能性增大,甚至可能发生超过上述频率的特大洪水。
The global warming has led to an accelerated water cycle and increased evaporation and precipitation. The middle and lower reaches of the Yangtze River in the 1990s have shown a clear warming trend, reaching 0.2 ~ 0.8 ℃, the maximum temperature in the Yangtze River Delta region. Precipitation in the middle and lower reaches of the Yangtze River increased significantly, the added value of 5% to 20%. In the 1990s, it was 10 years after the floods in the Yangtze River Basin in the 1950s. The Yangtze River Basin is the core area of China’s economic development. Analysis of the vulnerability of 725 flood-affected areas in the Yangtze River Basin shows that nearly one-third of the areas are flood-prone areas with high vulnerability. According to the 1998 socio-economic conditions, the possible losses from flood disasters in the 1954, 1991, 1996 and 1998 floods were estimated at 589, 55, 70 and 196 billion U.S. dollars respectively. Climate modeling predictions suggest that warming may reach 2.7 ° C in the Yangtze River basin in the 21st century, leading to a 10% increase in precipitation and a 37% increase in runoff. Under the common influence of the trend of global warming and the increase of impervious area and unit economic value resulting from the sustainable development of the social and economic areas in the region, the Yangtze River basin has the similarities between the years of thousand years, ten years and 20 years of 1870, 1954 and 1998 Increased probability of flooding, and even more than the above-mentioned floods may occur.