Changing nature of glaciers and glacial lakes make the Himalayas one of the most climate vulnerable regions on the planet. Rijan Bhakta Kayastha, a glaciologist at the Himalayan Cryosphere, Climate and Disaster Research Center, Kathmandu University in Nepal, speaks to DTE about glaciers in Nepal and the impact of climate change on them
The glaciers in Nepal are morphologically different from the glaciers elsewhere. How?
Nepal has summer accumulation-type glaciers because the country receives more than 80 per cent of its precipitation during the summer. Another characteristic of the glaciers is that the ice is covered with layers of debris such as soil, sand, rocks, pebbles and even big boulders.
If the thickness of the debris is more than 1 metre then the melting rate of the ice is slow. If the debris is thin — 2-3 centimetre — then the rate of melting becomes high. The debris absorb more solar radiation as they are black or brown in colour.
The energy budget on the glacier surface would be different with a little debris on the ice. These are the unique characteristics of the Himalayan glaciers in Nepal.
Has the snowfall pattern in the Nepal Himalayas changed recently?
We do not have data on snowfall for the Nepal Himalayas. What we do have is satellite data but it shows the snow cover and not the depth of the snow. We know the snow cover area is decreasing on a decadal scale. In terms of rainfall, no noticeable trend is visible.
But variations are visible in terms of temperature rise. The country’s maximum temperature increased by a significant 0.056 degrees Celsius per year between 1971 and 2014. The minimum temperature also increased, but the rate is lower at 0.002°C per year. The rising temperature makes the Nepal Himalayas vulnerable.
In the context of increasing temperatures, another important aspect is the settling of black carbon on the glaciers which increases the rate of melting. Is it impacting glaciers in Nepal?
The impact of black carbon deposition on the melting of ice from the Nepalese glaciers is relatively less. We have some data that it is impacting Tibetan and Indian glaciers. What we can also say is that not just the black carbon on the surface of the glaciers but atmospheric black carbon also increases air temperatures at higher altitude.
I recently reviewed a research paper that said that the increase in water vapour in the higher altitudes is leading to warming, as water vapour is a greenhouse gas. It found that during winters, the increasing water vapour in Nainital and Ladakh regions of India was increasing temperatures. A similar thing may be happening in the Nepalese glaciers, as well but we do not have data.
Nepal has 21 glaciers prone to glacial lake outburst floods. How are they monitored?
Nepal’s focus on studying glacial lakes picked up after the glacial lake outburst floods on August 4, 1985. The event caught everyone with surprise as it took place on a clear sunny day during the non-rainfall season. It was later found that the floods happened because a large chunk of glacial ice had fallen into the lake. But the event took place in a comparatively small lake and the country has several larger lakes where the impact will be higher.
The government now regularly monitors and mitigates potential glacial lake outburst flood events. In 2000, the Nepalese government reduced the depth of the Tsho Rolpa glacial lake by 3 m. In 2016, the country reduced the water level in Imja Tsho glacial lake in the Everest region by 3.4 m to mitigate potential glacial flooding events.
Nepal also has threats from 26 other glacial lakes (25 in China’s Tibetan region and one in India). This increases the number of potentially dangerous glacial lakes for Nepal to 47. We need early warning systems for these glacial lakes. Before 2000, the Nepal government had installed an early warning system for the Tsho Rolpa glacial lake. In 2014-15, another early warning system was installed for the lake. The downstream communities were also informed and trained about the measures to be taken if a glacial lake outburst flood takes place. We need to now increase awareness campaigns for mitigation and adaptation around other glacial lakes as well.
What are the challenges in monitoring and management of glacial lakes?
The first challenge is that glacial lakes are situated at high altitudes. Tsho Rolpa is at 4,500 m above sea level and Imja is at 5,000 m above sea level. The high altitude makes carrying out monitoring activities extremely difficult. The other challenge is the seasonality. We cannot work in the harsh terrains throughout the year. For instance, staying there during winters is not possible when snow covers the moraine area, making it difficult to work around the glacial lakes.
Can monitoring be done remotely through satellite imagery?
Yes, remote monitoring is possible. Many agencies are working on this. We are trying to get high-resolution satellite images. But one important thing to remember is that we cannot get the images in real time. We have to wait for a few hours or sometimes even days which means that by the time the images are available, the flood event would have already happened. We need early warning systems such as installing water level sensors and field film cameras. If the glacial lake breaches, then water level in the downstream will rise and the lake level will reduce, which do not get captured in satellite images. For these, we need field data.
Do you think glacial lakes can be managed by building hydroelectricity projects?
In the Tsho Rolpa glacial lake, the government has installed a micro hydro project of 15 MW capacity. The electricity generated by it is used by scientists for their field work. Even in the Imja glacial lake, the people wanted a hydroelectricity project, but the altitude did not allow for it. The government and power-producing companies want to generate hydroelectricity from other glacial lakes as well, but the main issue is that we do not know what will happen after 10 or 20 years.
For instance, we observed heavy rainfall events at altitudes of even up to 4,000 m above sea level in June 2021 and such events are increasing in frequency due to climate change. The government and companies are reluctant to build projects at higher altitudes because of the uncertainty regarding such extreme events. Building hydroelectricity projects at lower altitudes may not be economically viable in the future as the glacial lakes shrink and snowfall decreases further.
What other challenges can arise in making hydroelectricity projects ecologically sustainable?
There is not much of a problem in the case of micro hydroelectricity projects as they do not disturb the natural environment to a great extent. If we talk about plants greater than 20 MW then they might have a massive impact on the environment. For the Himalayan countries such power projects can be considered to be pretty big. These projects might have a negative effect on wildlife as well. There is currently a campaign going on in Nepal to not build big hydroelectricity projects inside national parks. I think not more than 10 projects are currently allowed inside national parks. The government also wants to bring in some rules to build big hydroelectricity projects.
This was first published in Down To Earth’s print edition (dated 16-31 January, 2022)
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