长江上游干旱灾害分析及防灾减灾措施

DROUGHT ANALYSIS IN THE UPPER BASIN OF CHANGJIANG RIVER AND DISASTER PREVENTION/ABATEMENT MEASURES

分析了长江上游历年干旱灾害发生的频率、危害程度和演变趋势。长江上游受太平洋高压和地形的影响，造成四川盆地西部和黔西北的春旱、盆东伏旱、盆中黔东北夏伏连旱，以及金沙江与大渡河的干热旱型。干旱的危害程度既受天气背景的影响，又与人类活动方式密切相关。异常的天气过程只有在人口密集、生产发达的地区才能形成显著的灾害。从近三百年的水文气象条件看，洪水发生略有加强，而干旱则略有减弱。但是近代工农业高速发展，人口密度加大，同样的天气异常产生的社会损失显著增大。另外森林砍伐、水源污染和过量抽取地面（地下）水等，都加剧了干旱的危害程度。长江上游的抗旱减灾应采取因地制宜、综合治理并重的方针，即结合大型水库屯蓄、水土保持、农田水利、作物调整、灾害预警和社会化服务等措施消减灾害。其中尤以长江上游防护林体系和大江河干流水库枢纽工程的作用巨大，可起到削蓄洪水、涵养水源、补给枯水量和改善生态环境的功效，是带根本性的流域治理措施。

In the paper the drought disaster and its occurrence,damage and changing tendency have been discussed for the upper basin of Changjiang River. Owing to the affection of summer Pacific High,there are wide drought regions in Sichuan basin and in northern Guizhou plateau.The valleys of Jin sha jiang, upper Ming jiang and Dadu River are typical dry hot lands owing to the effect of orographic rain shadow.The loss caused by drought depends not only on the extent of weather change,but also on the condition of human activities. The weather's abnormal change will cause serious disaster only in the area with dense population and vigorous economical activity.This is the reason of the increased calamity in recent hundred years.The types of land use, such as forest logging, water pollution, over using of groundwater,can also aggravate the extent of drought disaster. In order to reduce the disaster of drought in upper basin of Changjiang River,multi measurements for different areas and different situations should be taken,that is combining the approaches of reservoir storage, water soil conservation,farm land irregation, crops selection and drought warning, of which the large scale reservoir projects on large rivers and the protective forest system in upper basin of Changjiang River will take the key part.They can store runoff,reduce flood peak, conserve water resources, increase lowflow and improve the quality of eco environment,and constitute the fundamental measure for watershed reforming