尼泊尔洪灾何以威胁印度

尼泊尔和印度共享源自喜马拉雅山脉的复杂河流系统，这一地理特征使得尼泊尔发生的洪灾直接威胁到印度的安全。1 从尼泊尔流入印度平原的七至九条主要河流中，科西河和甘达基河等经常在印度北方邦，特别是比哈尔邦引发严重洪灾。1 比哈尔邦约四分之三的地区被官方列为易洪灾区。1

跨境洪灾的影响程度受多重因素制约。1 尼泊尔拥有超过6000条河流和溪流，大多向南流入印度和恒河，尼泊尔供应恒河平均年流量的约40%，在旱季这一比例更高。1 洪灾的严重程度不仅取决于尼泊尔的降雨强度，还受印度一侧的河流水位、堤坝状况、排水系统和气候变化等因素影响。1

历史灾害表明基础设施缺陷也是关键因素。1 2008年科西河灾难造成近400人死亡，但河流流量仅为堤坝设计承载量的十分之一，灾难主要由堤坝破裂引起。1 尼泊尔国内灾害规模通常为印度灾害的5到10倍，如2021年查莫利灾难造成200人死亡。1 随着极端降雨加剧和该地区变暖速度超过全球平均水平，跨境洪灾风险正在上升。1

Nepal's exposure to severe flooding poses a substantial threat to neighboring India, given the interconnected river systems originating in the Himalayas that traverse both nations. Between seven and nine major rivers flow from Nepal into Indian plains, with the Kosi and Gandak rivers particularly prone to triggering catastrophic floods in northern India, especially across Bihar state 1. The severity of such disasters depends not only on rainfall patterns in Nepal but also on conditions on the Indian side, including river water levels, dam integrity, drainage infrastructure, and the effects of climate change 1.

Nepal contains over 6,000 rivers and streams, the majority of which drain southward into India and the Ganges River system 1. The country supplies approximately 40 percent of the Ganges' average annual flow, with this proportion rising during the dry season 1. Roughly three-quarters of Bihar has been officially designated as flood-prone territory 1. The 2008 Kosi River disaster claimed nearly 400 lives, though the incident resulted primarily from dam failure rather than overwhelming water volume—the river's flow represented only one-tenth of the dam's design capacity 1. During monsoon season, typical flood warnings allow merely 12 hours to two days for preparation 1.

Recent climate patterns are intensifying extreme precipitation events in the region, where warming occurs at rates exceeding the global average 1. Nepal has experienced major disasters including the 2021 Chamoli incident, which killed 200 people, and the 2025 Dharali disaster involving landslides 1. Events originating in Nepal typically measure five to ten times larger in scale than comparable incidents in India 1.