snow cover in bhutan decreases by 1.74%, melt is faster at lower altitude

Snow covered areas in the Himalayas including Bhutan have been shrinking over the past decade. A study, ‘Monitoring of Snow Cover in the Hindu Kush-Himalaya,’ by a team of specialist from the International Center for Integrated Mountain Development (ICIMOD), revealed that snow covered areas in Bhutan decreased by an average of 1.74% over the past decade (2000-10).

Deo Raj Gurung, Remote Sensing Specialist, ICMOD, says that snow covered areas have been decreasing in Bhutan, prominently during spring and summer seasons.

“Depleting snow covered areas for central and eastern Hindu Kush Himalaya region is a concern to country like Bhutan dependent much on hydropower for revenue,” said Deo Raj Gurung.

The largest extend of snow covered areas in Bhutan over the past decade was in winter seasons with an average snow covered area of 14,485 square kilometers which is 37.7% of the total land area. It was followed by autumn season with 7788 sq.km (20.2%), spring 7788 sq.km (19.3%), and summer 4326 sq.km (11.2%).

Using the data, the team came up with a trend which shows that the average snow covered area in Bhutan decreased by 1.74%.

The snow accumulation starts as early as July and peaks in February. By March the melting commences and snow covered area is minimum in June. It has been found that the commencement of snow melt is delayed with altitude and contribution of snow over an altitude of 5,500 meters.

“After winter, the snow covered area starts to melt and it is time when the snow melt contributes to the rivers,” he said.

The team also carried out a study on the relationship between the altitude and snow distribution. It was found that higher the altitude more snow cover while the cover is less in lower altitudes.

Out of the twelve river basins of Bhutan that have been studied, on an average over the decade, Pho Chu basin had the maximum snow covered area where as Ha Chu basin had the least snow covered area.

However, the melting is faster at the lower elevations.

“There are various factors that contribute for the decrease in snowfall. One obvious example is climate change but we cannot be very conclusive only on the climate change,” said Deo RajGurung.