Above Barshaini the Parvati comes out of a narrow gorge, and on a night of heavy rain upstream it can rise a metre in an hour.

Nobody in the valley waits for an official warning. A shopkeeper in Pulga watches the water against a painted rock below his shop, and when it reaches the white line he calls a cousin in Kasol.

From Kasol the calls go on to the campsites along the bank, most of which now keep a list of numbers taped beside the kitchen door. Campers are walked up to the road before the water reaches the tents.

The chain has no name and no members' list. It began after the floods of a decade ago, when the river took two bridges and a row of cafes, and it has worked every monsoon since.