YK Poudel

Bhutan will experience a drastic increase in heat and rainfall over the coming decades, which will result in an increased number of flash floods, affecting agriculture, hydropower, and forestry – the most climate-sensitive sectors.

This is according to the ‘Climate Change Projection’ report launched recently by the National Centre for Hydrology and Meteorology (NCHM).

As per the NCHM data, Bhutan receives an average annual rainfall of 1,800 millimetres (mm), with maximum temperatures averaging around 23 degree Celsius and minimum of about 12 degree Celsius.

The country’s mountainous terrain makes it particularly vulnerable to extreme weather events such as floods, landslides, seasonal droughts, and glacial lake outburst floods (GLOFs).

The report states that the retreat of mountain glaciers is resulting in fluctuating water availability and increasing the risk of GLOFs, endangering lives and properties.

Bhutan has seen a sharper increase in both maximum and minimum temperatures, largely driven by greenhouse gas emissions and global socio-economic development. There has been a significant rise in temperatures observed since the 1960s and between 1991 and 2020.

The Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) states that Himalayan temperatures are rising, especially in Bhutan’s northern and western regions.

Historical precipitation trends in Bhutan show a complex pattern. Between 1950 and 2020, precipitation decreased until the 1970s followed by an increase, particularly from the 1990s onward.

According to the IPCC projections, heavy precipitation will continue to rise throughout the 21st century, with the most significant increases expected under higher emission scenarios.

The northern, western, north-western, and south-western regions of Bhutan are likely to see the greatest rise in precipitation, increasing the risk of floods. Conversely, some eastern and southeastern areas may experience reduced rainfall, potentially leading to seasonal droughts or water scarcity.

In the near to mid-term, accelerated glacial melt is expected to enhance water availability in river basins but also increase the risk of GLOFs. Over the long term, however, a reduction in glacial runoff could lead to higher chances of seasonal droughts, particularly in regions where rainfall is also expected to decrease. The Wangchhu basin is anticipated to be particularly affected by reduced glacial runoff.

Densely populated areas across the country are expected to face higher temperatures and increased rainfall, impacting agriculture and infrastructure. Major rice-producing regions in the east may face water shortages, while areas in the west, south, and north could experience flood-like conditions.

By 2040, climate projections suggest that rainfall distribution will vary from the baseline, with northern, western, central, and south-western dzongkhags likely to see increased precipitation. Wangdue, Gasa, Punakha, Bumthang, and Thimphu are expected to experience the highest increases. In contrast, eastern and south-eastern districts might receive less rainfall.

By 2060, precipitation is expected to increase across the country, with the most significant rises in the northern, western, central, and south-western dzongkhags. However, the eastern and south-eastern districts may continue to receive less precipitation, indicating potential water scarcity.

By end of the century, all dzongkhags in the country are likely to experience at least a 56mm increase in total annual precipitation compared to the baseline, with the highest increases expected in Punakha, Gasa, Thimphu, Paro, Bumthang, and Wangdue. This would also mean at least 2 degree Celsius increase in minimum temperatures even during the winter months.

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