Bhutan’s glaciers contribute significantly to total water resources

Bhutan’s economy relies heavily on hydropower and agriculture. Sale of electricity to India contributes almost 20 percent to the national revenue and agriculture constitutes 20 percent of the country’s GDP. But rising global temperature, change in land use and deforestation are raising new concerns of how decreasing water volume would impact these two prominent economic sectors.

Glaciers, rain, ground water and snow-melt are the major sources of water that make up Bhutan’s overall water resources. Almost all of Bhutan’s rivers originate from the glaciers and their volume increases as they move downstream with additional water coming from rain and spring. A study conducted by the National Center for Hydrology and Meteorology and Sherubtse College concluded that glaciers contribute on average 14-31% and 49% to total water availability in Chamkhar Chhu and Pa Chhu respectively.

Stable isotopes of water and geochemistry data were employed to study glaciered headwater river basins of Chamkhar Chhu and Pa Chhu in 2014-2017 and 2021, respectively. Dendup Tshering, Lecturer, Sherubtse College said these techniques leverage the distinct isotopic and geochemical signatures in the waters originating from different sources and flow paths to understand dominant contribution to the river flow such as glacier melt water or rainwater. “While rain contributes a significant portion to total stream flow, the contributions from glaciers is lot more than previously understood,” he said.

In 2011, the Norwegian Water Resources and Energy Directorate conducted a study on the climate change impacts on the flow regimes of Bhutan’s river and its consequences for hydropower development. The study found that glaciers contribute on average between 10 to 15 percent to the total water availability in Bhutan’s river systems. Dendup Tshering said the study area extends from the high elevation Jichudrakey glacier down to Chunzom (Pa Chhu and Thim Chhu confluence) for Pa Chhu and Thanagang glacier down to Chamkhar for Chamkhar Chhu.

Glacial melt will therefore seriously deplete Bhutan’s water resources that drive the hydropower and agriculture sector. Bhutan is home to around 983 glaciers and 2,800 glacial lakes. The latest IPCC report of ICIMOD said that the melting and receding of glaciers in the Himalayas is a phenomena that is “locked in” and cannot be reversed. To gauge the rate of glacial melt in the Bhutan Himalayas, two studies were conducted in the Gangju La and Thana glaciers by NCHM in 2020. Between 2004 and 2019, Gangju La retreated at an average rate of 11.4 meters while Thana retreated by 18.2 meters annually.

Another research evaluating glacier melt contributions to Chamkhar Chhu mentions that the average glacier retreat is higher in Bhutan than in Nepal due to higher precipitation and temperature in eastern Himalayas.

In 2019, NCHM officials observed huge melting of ice in one of Bhutan’s largest glacial lake, Thorthormi tsho, due to temperature spike and delayed monsoon. The government issued a flood advisory. Weather extremities are expected to become more pronounced and frequent as climate change worsens. This means during dry season in winter, water volume in Bhutan’s river system will experience further decrease in volume.

Although more hydropower projects are being built to increase the supply of hydroelectricity and generate more revenue for the economy, the changing scenario and new data that shows increasing contribution of glaciers to water resources, means the government must re-strategize hydropower development in the country, before the trend of rapid glacier melt start affecting water flow and volume

There is an urgent need to diversify Bhutan’s energy basket and invest in other renewable sources of energy including wind and solar. To ensure energy security in South Asia, it is necessary to strengthen energy cooperation through exploring new market mechanism, trilateral arrangements and regional grid connection. Further, since Bhutan’s prominent economic sectors rely heavily on the availability of water, Bhutan and India must extend its cooperation to invest in other types of renewable energy besides hydropower to ensure energy security.

The story is being covered by the Institute of Happiness for a research conducted on the effects of cross border energy trade.

Contributed by Nidup Gyeltshen