科西河跨境流域水旱灾害与防治

On the Water Hazards in the Trans-Boundary Kosi River Basin

科西河流域是恒河的一个重要支流,地跨中国、尼泊尔和印度3个国家,流域面积7.15万km2,流域具有世界上最大的高差(从海拔8 848 m的珠穆朗玛峰到海拔60 m的恒河平原),最为完整的气候、土壤和植被带谱。流域发育有罕见的多类型水旱灾害,主要有冰湖溃决、洪水、干旱、水土流失等。通过实地调查这一代表性跨界流域的水文、气象、地质、地貌、土壤植被和区域社会经济等基本特征并结合已有的研究资料,揭示流域冰湖溃决、洪水、干旱等水旱灾害的特征和时空发育规律。流域冰湖溃决灾害集中于科西河流域上级支流,灾害损失巨大,并由于溃决洪水的侵蚀,沿途链状滑坡泥石流灾害发育;洪水灾害主要集中于流域下游,在相对较高标准的防洪体系中,洪水灾害是自然因素和人为因素相结合产生的,并造成流域水土流失严重;干旱灾害范围大,年内持续时间长,并且由于人口增加和生态退化进一步严重化。最后,依据流域水旱灾害特点,提出一系列减灾策略与措施。

The Kosi River is an important tributary of the Ganges that passes through China, Nepal and India. With a basin area of 71 500 km2, the Kosi River has the largest elevation drop in the world （ from 8 848 m of Mount Jolmo Lungma（ Mt. Everest） to 60 m of the Ganges plain） and covers a broad spectrum of climate, soil, vegetation and socioeconomic zones. The basin suffers from multiple water related hazards including glacier-lake outburst, debris flow, landslide, flood, drought, soil erosion and sedimentation. This paper describes the characteristics of water hazards in the basin based on the literature review and site investigation covering hydrology, meteorology, geology, geomorphology and socioeconomics. Glacier-lake outbursts are a huge threat to the local population in the region and usually further trigger landslides and debris flows. Floods are usually a result of interaction between man- made hydraulic structures and the natural environment. Droughts; tend to last over long periods and affect vast areas. Debris flows are widespread and occur in clusters. Rapid population increase, decline of ecosystems and climate changes have further exacerbated water related hazards in the region. Finally, the paper has proposed a set of mitigating strategies and measures.