LAST year was the driest in more than three decades for the world’s rivers, a United Nations weather agency has reported. 

The World Meteorological Organisation (WMO) also said glaciers that feed rivers in many countries suffered the largest loss of mass in the last five decades, warning that melting ice can threaten long-term water security for millions of people globally.

Global temperatures last year were around 2.1° Fahrenheit (1.2° Celsius) above the average baseline period (1951-1980) used for the measurement by the US National Aeronautics and Space Administration — making it the hottest on record.

Experts say the summer of this year was recorded as the hottest summer ever — raising the prospects for a possible new annual record.

The record-high temperatures contributed towards a drying up of water flows and prolonged droughts in an increasing number of locations across the planet. 

“Water is the canary in the coal mine of climate change. We receive distress signals in the form of increasingly extreme rainfall, floods and droughts which wreak a heavy toll on lives, ecosystems and economies,” said WMO secretary-general Celeste Saulo, releasing the report today.

Ms Saulo said rising temperatures had, in part, led the hydrological cycle to become “more erratic and unpredictable” in ways that can produce “either too much or too little water” through both droughts and floods.

The weather agency, citing figures from UN Water, says some 3.6 billion people face inadequate access to water for at least one month a year — and that figure is expected to rise to 5 billion by 2050.

“In the (last) 33 years of data, we have never had such a large area around the world which was under such dry conditions,” said Stefan Uhlenbrook, director of hydrology, water and cryosphere at WMO.

The report said the southern US, Central America and South American countries Argentina, Brazil, Peru and Uruguay faced widespread drought conditions.

The authors of the report also said they had recorded “the lowest water levels ever observed in the Amazon and in Lake Titicaca,” on the border between Peru and Bolivia.

The WMO said half of the world faced dry-river-flow conditions last year.