Nepal's devastating floods have exposed a risk that does not stop at its borders. This was reported by Qazaqyia.kz citing BBC News.
India and Nepal share the rivers that rise in the Himalayas, but the relationship between a flood in Nepal and a disaster in India is more complicated than a simple story of water flowing downstream, say experts.
Some floods can race out of the mountains carrying enormous quantities of mud, rock and debris. Others may lose much of their force as they reach the plains, leaving behind a more conventional flood.
And whether that water becomes a disaster in India depends not only on how much rain has fallen in Nepal, but also on rainfall, river levels, embankments, drainage and development on the Indian side.
Nepal's floods are a warning for India - not simply because water flows south across the border, but because the two countries share a vast and increasingly volatile Himalayan river system.
Nepal has more than 6,000 rivers and streams, most draining south into India and the Ganges.
Three major systems dominate: the Kosi in the east, the Gandaki (Gandak in India) in the centre and the Karnali (Ghaghara in India) in the west, with the Mahakali (Sharda) along the western border.
A dozen smaller rivers rising in the Siwaliks and Chure - including the Bagmati, Kamala, Rapti and Babai - are less famous but can produce faster, more unpredictable floods because their catchments are small and steep.
Seven to nine major rivers flow from Nepal into the Indian plains, and they are responsible for flooding in India, according to Manish Shrestha, a hydrologist at the International Centre for Integrated Mountain Development (ICIMOD).
India's Central Water Commission identifies the Kosi, Gandak, Bagmati and Ghaghara as some of the main transboundary rivers.
Bihar is by far the most exposed Indian state, with roughly three-quarters of north Bihar officially classified as flood-prone.
Almost all the major rivers that flood the state originate in Nepal, with the Kosi - the "sorrow of Bihar" - the most notorious, followed by the Gandak, Bagmati and Kamala.
Eastern Uttar Pradesh is vulnerable to the Ghaghara, Rapti and Gandak rivers. Districts like Gorakhpur, Bahraich, Lakhimpur Kheri and Shravasti are regularly affected.
Uttarakhand state shares the Mahakali-Sharda rivers. North Bengal receives the Mechi and Mahananda.
"Bihar dominates in scale. Uttar Pradesh is second and often under-reported," says Pradeep Man Dangol, hydrologist at ICIMOD.
Bihar bears the greatest burden, but Uttar Pradesh is a significant and often overlooked part of the risk.
Think of it as a three-part chain, say hydrologists.
First, the rain: where it falls and how heavily.
Flood peaks reaching India are often generated not in the high Himalayas but lower down, in the Siwaliks, Chure and Terai, where intense monsoon rain can fall on steep, small catchments.
Nepal's rivers cross a sharp break in slope at the mountain front, drop their sediment, and spread across the plains as braided, shifting channels.
How bad the flooding becomes depends on what the water encounters - the volume of rain on the Indian side, how full the Ganges is, embankments and barrages, and blocked drainage from roads, railways and settlements on the floodplain.
So the peak flow at the border is largely determined by rainfall in Nepal. The severity of flooding depends at least as much on conditions in India.
The 2008 Kosi disaster shows why: the river was carrying far less water than the embankment was designed to handle. The catastrophe was caused by the embankment failing, not by an exceptional flood.
"For the peak flow arriving at the border, largely Nepal's rainfall; for the severity of flooding once it arrives, at least as much on Indian conditions," says Saswata Sanyal, ICIMOD's intervention manager for disaster risk reduction.
The 2008 Kosi disaster is a powerful illustration.
Nearly 400 people died in Bihar after the Kosi breached an embankment in Nepal. But, remarkably, it was not an extraordinary high-flow event on the river.