Bihar opens all 36 gates at Valmiki Nagar as the Gandak, Ganga and Kosi sit above danger marks

Bihar's water resources department opened all 36 gates of the Gandak barrage at Valmiki Nagar on Friday and sent 1.02 lakh cusecs downriver by 5 p.m. The release followed a surge that began in Nepal's Rasuwa district on 26 August, when ice and rock collapsed near the China border and pushed a wall of water into the Trishuli-Narayani-Gandak system.

The department's Friday bulletin put five rivers above the danger mark at one or more stations: the Gandak, Kosi, Ganga, Burhi Gandak and Ghaghra. The Gandak had crossed the mark in Gopalganj. The Kosi and Burhi Gandak had reached it in parts of Khagaria, Katihar and Kursela. The Ganga was above the mark at Digha, Hathidah and Gandhighat in Patna and at Kahalgaon in Bhagalpur. The Ghaghra was above it at Darauli in Siwan.

On 27 August the Central Water Commission had already flagged a sudden rise in the Trishuli at Furke Khola and warned that the pulse could travel into the Gandak. At Dumariaghat in Gopalganj the Gandak stood at 62.53 metres against a danger level of 62.22. At Lalganj in Vaishali it was 50.63 metres against 50.50.

Why this flood is not a Kosi flood

Bihar's flood calendar is usually written by the Kosi, the Bagmati and the Kamla-Balan. Those rivers rise when rain or a breach hits a different set of Nepali catchments. The Rasuwa event sits on the Trishuli-Narayani line, which becomes the Gandak after it crosses at Valmiki Nagar. That is why Gopalganj, Vaishali and the Patna Ganga stations are the first Indian numbers to move, and why a Kosi district can look quiet on the same day a Gandak village is told to leave.

The CWC list of Nepal-origin rivers that can flood Uttar Pradesh and Bihar is long: Ghaghra, Sharda, Rapti, Gandak, Burhi Gandak, Bagmati, Kamla, Kosi, Mahananda. Each enters India at a different point. A disaster in one Nepali valley does not automatically fill every Indian basin. Officials who treat "Nepal flood" as a single incoming wave misread the map.

Debris as a second problem

By Saturday, Patna officials were talking less about a new peak and more about what the peak had carried. Soil, stone and wreckage from the Nepali hills are moving downstream. Embankment crews have been told to watch for scouring and for debris piled against the face of a bund. Water levels had dropped at some gauges. They remained close to or above danger at others. The hill catchments, officials said, have not stabilised.

Uttar Pradesh is in the same system. The Gandak and Ganga stations there are on the same alert list. Three unidentified bodies were pulled from the Gandak at Kushinagar on Friday, along with vehicles, cylinders and furniture. That is the flood arriving as wreckage rather than as a forecast sheet.

Low-lying settlements in the affected Bihar districts have been moved to higher ground. The operational fact that matters on Saturday is simpler than the basin lecture: the barrage is wide open, five rivers are still high, and the next pulse from Rasuwa would travel the same channel that is already full.