By Passang Norbu
Contrary to the general notion, one often associated with climate change, melting of glaciers will not necessarily mean the disappearance of the country’s many river systems.
Glaciers do contribute to the country’s hydropower generation, but that according to a study carried out by Druk Green Power Corporation (DGPC) in cooperation with the Norwegian government in 2011, shows their contribution is only about 10 percent.
The study titled “Climate change impacts on the flow regimes of rivers in Bhutan” went on to prove that even if the Himalayan glaciers melted without a trace, there would still be sufficient water for electricity generation.
Water in the Bhutanese rivers, the study stated came from melting of snow and glaciers, storages in lakes and wetlands.
Most essentially, the study said it came from rainwater that has been stored underground in watersheds.
Therefore, DGPC managing director Dasho Chhewang Rinzin said it was a misconception that climate change and glacial retreat would affect the country’s hydropower sector and the economy consequently.
“Eighty percent of the water that generate electricity comes from watersheds,” he said.
A watershed is any area surrounding the river valley with thick vegetation and has a gradient sloping towards the river so that stored ground water flows to it.
Forestry director Chencho Tshering in an earlier interview said there was a need to shift focus from melting glaciers to preserving watersheds instead.
“Glacial melt is almost natural, but water sheds can be preserved,” he said. “Given that the hydropower sector is going to be our economy’s backbone, forest cover, that preserve water sheds should be viewed as a critical resource.”
Officials from the watershed management division said at the sources where glaciers form a river, the volume of water is relatively small, which as they reached the valleys increased in volume.
“This is because water that has been stored underground in watersheds flow into the river and adds up to its volume,” one official said. “As of today we can comfortably say our watersheds are rich.”
So far the forestry department has identified around three critical watersheds along Dagana, Tsirang and Wangduephodrang.
Most streams that have their sources in a water shed are perennial, the sheds store enough water underground that it flows through it even during the dry season.
With forest degradation, these type of streams would become seasonal bringing flash floods during wet season.
“Flash floods occur when the watersheds are damaged,” one forestry official said. “With poor vegetation, water will not be intercepted and the entire rainwater that hits the ground will flow from the surface.”
Forest fire has been identified as the biggest threat to watersheds.
“Forest fires destroy the vegetation that intercepts rain water and hence water flows from the surface without being stored,” he said.