A view of Thorthormi Lake. Image credit: National Centre for Hydrology and Meteorology

Bhutan has been threatened as the water level of its largest glacial lake – Thorthormi Tsho (lake) – has risen almost two metres following melting of the ice and snow in the lake.

According to a thethirdpole.net report, the melting has been caused by sustained heat waves, a delayed monsoon and a spike in the temperature.

Following the development in Thorthormi Tsho, the Bhutan government issued a nationwide advisory. Besides, a team of senior hydrologists, technicians and glaciologists inspected the site in Lunana for monitoring the situation.

It has been reported that any major disturbance on Thorthormi Tsho might create a glacial lake outburst flood (GLOF) which would cause huge loss of both human and wildlife, infrastructure and property.

The report also said the satellite images of the lake show melting on the largest lake of the Himalayan nation which took place in a period between June 6 and June 15, 2019.

Excess waters were drained out to two smaller lakes in the downstream on June 20, 2019 but due to weak moraine entrapment, there was outburst in one of the two smaller lakes, the report said.

The outburst caused flood which washed away a small bridge in a nearby village in Thanza. Besides, the villagers of three other villages located near the lake had to be evacuated.

This also exposed an Automatic Water Level Sensor (AWLS) on one of the lakes, said the report, adding that the sensor had to be re-located later

The report quoted senior glaciologist Karma Toeb of the National Centre for Hydrology and Meteorology (NCHM) of Bhutan as saying that the “excess water was due to the melting of ice in the glacier lake”.

It has also been reported that the glacier lakes have been forming and expanding all over the Hindu Kush Himalayas due to climate change in the recent years.

The report further quoted NCHM officials as saying that the rise in temperature in the month of June last was due to the sustained heat wave which had lasted for 30 days.

The report quoted hydrologist Sangay Tenzin as saying that currently the moraine dam has sufficient mass to withstand the hydrostatic (water) pressure from the Thorthormi Lake.

But if melting in the lake continues due to rise in temperature the moraine will not be able to hold it, he added.


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