One of the Amazon’s main tributaries has dropped to its lowest level ever recorded, Brazil’s geological service said on Friday, reflecting a severe drought that has devastated the Amazon rainforest and other parts of the country.

The level of the Negro river at the port of Manaus was at 12.66 metres (41ft) on Friday, as compared with a normal level of about 21 meters (69ft).

It is the lowest since measurements started 122 years ago.

The previous record low level was recorded last year, but toward the end of October.

The Negro’s water level might drop even further in coming weeks based on forecasts for low rainfall in upstream regions, according to the geological service’s predictions.

Andre Martinelli, the agency’s hydrology manager in Manaus, was quoted as saying the river was expected to continue receding until the end of the month.

Water levels in Brazil’s Amazon always rise and fall with its rainy and dry seasons, but the dry portion of this year has been much worse than usual.

All of the major rivers in the Amazon basin are at critical levels, including the Madeira river, the Amazon’s longest tributary.

The Negro drains about 10% of the Amazon basin and is the world’s sixth-largest by water volume.

Manaus, the biggest city in the rainforest, is where the Negro joins the Amazon.