Some 15 million people worldwide are at risk from flooding caused by glacial lakes, half of them in India, China, Pakistan and Peru, according to the latest study published in the journal Nature Communications. As the most densely populated mountain country in the world, Nepal is at higher risk. Glacial Lake Outburst Floods (GLOFs) in the Nepal Himalaya can be even more catastrophic for towns along valley floors as well as downstream infrastructure. <a href="https://www.nepalitimes.com/banner/climate-smarter-himalayan-infrastructure">What happened in Melamchi </a>in July 2021 is a sign of things to come. Nepal’s largest infrastructure project to supply water to Kathmandu was nearly destroyed by a massive debris flow after a cloudburst upstream in the Langtang National Park. “What make GLOFs worse in Nepal is that they are often combined with the monsoon,” explains watershed expert Madhukar Upadhyay. “Every year we have seasonal floods. When a weakened moraine is breached, more water is added to already swollen rivers. Making matters worse is high-intensity rainfall in higher altitudes as we saw in Manang in 2022.”&nbsp; Read more: <a href="https://www.nepalitimes.com/opinion/climate-risk-to-hydropower-investment/">Climate risk to hydropower investment</a>, Ajaya Dixit  <figure> <img src="https://publisher-publish.s3.eu-central-1.amazonaws.com/pb-nepalitimes/swp/asv65r/media/20230602040624_e60a90be970842d53f6e236b1a59612c82aa035635a3ae4838481a31710f1446.jpg" data-media-id="editor_2" data-image-id="20230602040624_e60a90be970842d53f6e236b1a59612c82aa035635a3ae4838481a31710f1446" data-rendition-name="original" width="853" height="640" loading="lazy" alt="Melamchi amage NT"> <figcaption>The damage from a massive debris flow on the Melamchi River in June 2021 to the channel diverting water from the Melamchi to the tunnel at the project headwork. Photo: SHIVA BASKOTA</figcaption> </figure>  Scientists say that the permafrost binding loose moraine material is also melting, and without the cementing action of the ice the moraine walls can collapse easily in heavy precipitation. Rain falling where there used to be snow is making matters worse.&nbsp; <a href="https://www.nepalitimes.com/here-now/living-below-nepal-s-melting-mountains">The Himalaya is melting</a> faster than the global average, and even in the best-case scenario, the mountains will lose more than one-third of their ice by 2100.&nbsp; A paper published in the journal Climate and Atmospheric Science last year revealed that the rate of ice loss on the South Col of Mt Everest is shocking: what took 2,000 years to accumulate is melting in a mere 25 years.&nbsp; Read also: <a href="https://www.nepalitimes.com/banner/tracing-past-glacial-floods-in-kangchenjunga/">Tracing past glacial floods in Kanchanjunga</a>, Alton C Byers  <figure> <img src="https://publisher-publish.s3.eu-central-1.amazonaws.com/pb-nepalitimes/swp/asv65r/media/20230602040632_f3e5d9e3eb4dca842d715afab7ee68899e0fa3c0d2f9f039d9b288b1492f4955.png" data-media-id="editor_5" data-image-id="20230602040632_f3e5d9e3eb4dca842d715afab7ee68899e0fa3c0d2f9f039d9b288b1492f4955" data-rendition-name="original" width="891" height="500" loading="lazy" alt="Map"> </figure>  There are 3,252 glacial lakes in Nepal, including the Khumbu Glacier where Base Camp is now 50m lower than when Hillary and Tenzing climbed Everest<a href="https://www.nepalitimes.com/here-now/everest-70-years-on"> seventy years ago</a>.&nbsp; Imja was a debris covered glacier on trekking maps even 25 years ago, but is now a 2km long lake. Tso Rolpa glacial lake at 4,580m in the Rolwaling Valley has grown seven times in size in the past 60 years. “There is a lot of evidence that the number of glacier lakes in Nepal and worldwide is increasing,” says Miriam Jackson, glaciologist with the International Centre for Integrated Mountain Development (ICIMOD). “The size of existing lakes is also increasing. For example, the area of glacier lakes increased by 12% in the Kosi basin and 8% in the Gandaki basin.” The water level in Imja has been lowered by 3.4m and by 3m in Tso Rolpa at a cost of $7.2 million and $9 million respectively. Scientists now say the water level in Tso Rolpa needs to go down by another 20m to reduce risk of bursting. Read also: <a href="https://www.nepalitimes.com/here-now/danger-nepal-s-glacial-lakes-are-filling-up">DANGER: Nepal’s glacial lakes are filling up</a>  <figure> <img src="https://publisher-publish.s3.eu-central-1.amazonaws.com/pb-nepalitimes/swp/asv65r/media/20230602040628_4ac8ea629de0f69bfb27fe9b783f126c7eea6dcadda7e812436d393d7c21c13e.jpg" data-media-id="editor_8" data-image-id="20230602040628_4ac8ea629de0f69bfb27fe9b783f126c7eea6dcadda7e812436d393d7c21c13e" data-rendition-name="original" width="1843" height="1000" loading="lazy" alt="Imja lake NT"> <figcaption>A frozen Imja Lake looking east from the outlet. Photo: SHARAD JOSHI</figcaption> </figure>  There are other potentially dangerous lakes like Thulagi below Himalchuli, and new lakes are emerging on both sides of the Himalaya in China and Nepal that have not even been mapped. Nepal’s glaciers are shrinking three times faster than in 1998 and Jackson says that the possibility of flooding, whether from glacial lakes or other sources, is taken into account when building close to the rivers. When Nepal’s only reservoir project on the Kulekhani was commissioned in 1982, engineers had designed it to function for 100 years. But a cloudburst in the catchment area in 1993 deposited so much debris into the lake that its lifespan was reduced by 30 years. “Melamchi and Kulekhani are proof that the entire Himalayan region including Nepal are not suited for mega projects. Our focus and investment should instead be on multiple small-scale projects spread out across the country,” says watershed expert Madhukar Upadhyay. As for infrastructure already under construction, there are several mitigating measures that can be deployed, such as early warning and real-time information systems in the catchment area, not only about rainfall but GLOFs and landslide blocked rivers. Experts say Nepal and the countries in the Himalaya should not overlook the phenomenon of permafrost melting that is making the mountains and moraines much more prone to erosion. Permafrost is a thick subsurface layer of frozen soil that is generally not visible and thus harder to identify. Besides Melamchi, thawing permafrost is thought to have been partly responsible for the Chamoli disaster in the Indian Himalaya in 2021. Read also: <a href="http://archive.nepalitimes.com/news.php?id=2391#.XoyO8MgzbIU">The day after tomorrow in the Himalaya</a>, Navin Singh Khadka “Generally, moraines have an ice core, which is one reason why moraine-dammed lakes are so dangerous. The ice could be hundreds or even thousands of years old and melt very slowly but the moraine is constantly settling,” explains Jackson. “Thawing permafrost makes mountains unstable, thus causing rockfalls. If there is a landslide into a glacier lake, then that could trigger a flood.” GLOFs also have a transboundary dimension since so many of Nepal’s rivers and their tributaries originate in glaciers in Tibet. Of the 47 high-risk glacial lakes in Nepal, 20 of them start in Tibet (see map, below). Mitigating measures such as artificially lowering the water level are expensive which makes cross-border early warning of GLOFs so crucial. ICIMOD has launched the Kosi Initiative with a transboundary working group collaborating with the Chengdu-based Institute of Mountain Hazards and Environment (IMHE) and others. It has also done computer modelling of flood hazard and an assessment called WeACT that integrates local knowledge with science to improve community preparedness. But GLOF risk can be reduced if vulnerable communities are aware of the danger, are given decision-making powers and have the resources to be prepared, as has been seen in Chunkung in Khumbu and Langtang, where villagers are adapting to climate change by building embankments on their own, and avoiding construction along river banks. Says Madhukar Upadhyay: “We need to strengthen our local science to better understand the geology and glaciology, make local communities and the national government aware of the dangers and take the risk into account in building settlements, hydropower plants, bridges and roads.” &nbsp; Read also: <a href="https://www.nepalitimes.com/banner/human-face-of-a-himalayan-climate-crisis/">Human face of a Himalayan climate crisis</a>, Rastraraj Bhandari

Sonia Awale

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For destruction, ice is also great and will suffice

<figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221109111140/636b83d99c7e80680e06775ejpeg.jpg" alt="" width="1843" height="1000"/><figcaption>A frozen Imja Lake looking east from the outlet. Photo: SHARAD JOSHI</figcaption></figure>It is now looking doubtful if countries around the world can cut their greenhouse gas emissions as agreed in Paris six years ago, so that global temperature rise will be limited to 1.5 Celsius by 2050. The earth is going to heat up by more than that.Even if it is 1.5 Celsius, the average temperature in the Himalaya will go up by 1.8 degrees because of a phenomenon called ‘altitude effect’. The best-case scenario is that one-third of all remaining Himalayan glaciers will have melted during this century. However, if greenhouse gas emissions continue to rise at the present rate, two-thirds of Himalayan ice will be gone by 2100.All this will have a catastrophic effect on water supply for 1 billion people downstream on rivers that originate in the Himalaya, as well as throw off kilter weather systems.  It will also increase the danger of <a href="https://www.nepalitimes.com/here-now/nepals-glacial-lakes-in-danger-of-bursting/" target="_blank" rel="noopener noreferrer">glacial lake outburst floods</a> (GLOF) within Nepal.Till the 1960s, the Imja Glacier near Mt Everest had only a few melt-pools. Since then, the ice has been replaced by a lake nearly 2km long, 600m wide and up to 150m deep. The ice is receding 70m a year.As glacial lakes expand, there is a danger of them bursting due to water pressure, or because of earthquakes and avalanches falling into them. As the average temperature in the mountains rises by 0.056 Celsius every year, the threat of glacial lake outbursts will only grow.On top of the perennial risk of earthquakes, new hydropower stations, highways along rivers, bridges and towns will also have to take into account the threat of GLOFs. The flash flood near <a href="https://www.nepalitimes.com/latest/non-climate-cause-of-nanda-devi-flood/" target="_blank" rel="noopener noreferrer">Nanda Devi in India’s Uttarakhand state</a> in March washed away two hydroelectric plants that were under construction.There is a warning there for Nepal, which is building cascade projects on the two Bhote Kosi rivers that flow down from China, Tama Kosi, Marsyangdi, and the Arun. In the Gandaki Basin is the particularly dangerous Thulagi glacial lake below Himalchuli, which would directly threaten three major hydroelectric projects along the Marsyangdi River. Scientists monitoring Thulagi have found the glacier has receded by 2km since 1984, the ice replaced by a lake.<a href="https://www.nepalitimes.com/banner/tracing-past-glacial-floods-in-kangchenjunga/">Tracing past glacial floods in Kanchanjunga</a>, Alton C Byers<figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221109111140/636b83dc9c7e80680e06775fjpeg.jpg" alt="" width="1500" height="1080"><figcaption> </figcaption></figure>“If Thulagi were to burst, the flood would go down 100km downstream on the Marsyangdi and Narayani, taking out hydroelectric projects, highways and towns along the way,” says Pradeep Mool, a glacial scientist formerly with ICIMOD.A survey last year showed that GLOF risk is highest in eastern Nepal. There are 42 dangerous lakes on the Kosi basin alone, like Imja, Tso Rolpa, Lower Barun and Hongu. The bursting of any one of these would send a wall of water and debris downstream to the Kosi.There is also the danger of <a href="https://www.nepalitimes.com/editorial/more-himalayan-tsunamis/" target="_blank" rel="noopener noreferrer">transboundary GLOFs</a>. In the past, even the bursting of relatively small glacial lakes in Tibet have caused major damage in Nepal. The earliest recorded one was in 1934, when a flash flood from a glacial lake burst in Tibet caused destruction along the Bhote Kosi.In 1981, another glacial lake burst in China caused a flood on the same river in Nepal, damaging the Sun Kosi power plant and washing out a 25km section of the Arniko Highway, cutting Nepal’s only road to China for three years.<figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221109111140/636b83e09c7e80680e067760jpeg.jpg" alt="" width="1000" height="1506"><figcaption> </figcaption></figure>Of the 47 very dangerous lakes that threaten Nepal’s valleys, 25 originate in glaciers in Tibet. Since 1977, there have been at least 20 GLOFs of which 14 were caused by glacial lakes in Nepal bursting, and the rest were in China.To understand what a GLOF looks like, we have the<a href="http://archive.nepalitimes.com/article/nation/Anatom-of-a-Himalayan-tsunami,1330" target="_blank" rel="noopener noreferrer"> Seti flood of 2012</a> which killed nearly 70 people north of Pokhara. Although not caused by a glacial lake burst, it demonstrated the destructive power of such a flood.Although Nepalis may not be responsible for global heating, it does not mean we can sit back and do nothing. While scientists try to figure out exactly how fast the glaciers are melting, Nepal’s policy-makers need to start planning to be prepared for floods that are bound to be unleashed.The danger of GLOFs are compounded by Nepal also being on a seismically active zone. Many of these fragile Himalayan glacial lakes could burst simultaneously during a large earthquake.<img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221109111140/636b83e39c7e80680e067761jpeg.jpg" alt="" width="1369" height="630">This calls for hazard mapping, early warning systems through SMS or radio, as well as mitigation efforts like those carried out to <a href="https://archive.nepalitimes.com/article/from-nepali-press/Diverting-danger,3172" target="_blank" rel="noopener noreferrer">reduce water levels on Imja</a> and Tso Rolpa. The microhydro scheme on the Langtang Lirung Glacier that reduces the water level on a recently-formed glacial lake, and also generates electricity could be a model for other remote valleys in Nepal.Because glacial lakes are located at such high altitudes in remote roadless areas, lowering their water level can be expensive. Most of the equipment has to be flown in by helicopter, and work is often hampered by altitude and weather. The question is: who should pay for these risk-reduction measures?“Even if the water level is reduced they can burst and come down like tsunamis, we have to keep monitoring the lakes, and install effective early warning systems in Tso Rolpa and Imja to at least save lives if we cannot save the infrastructure,” says Sarju Baidya of the Department of Hydrology and Meteorology.There are no feasible methods to prevent a glacial lake from bursting, and it is not in our power to stop the lakes expanding. So the only thing Nepal can do is to reduce the level of the most dangerous lakes, design downstream infrastructure taking the dangers into account, and to have an early warning system.Says Pradeep Mool: “What we can do immediately is to install measurement stations and monitor them by satellite, prioritise the high-risk lakes for site inspections to gauge the strength of the moraines, and make a short list of the most dangerous ones for early warning, and mitigation measures.”Read also: <a href="https://www.nepalitimes.com/banner/human-face-of-a-himalayan-climate-crisis/">Human face of a Himalayan climate crisis</a>, Rastraraj Bhandari

DANGER: Nepal’s glacial lakes are filling up

<figure><img width="2560" height="1967" src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221110111152/636cd8519c7e80680e092e37jpeg.jpg" alt=""/><figcaption>The origin of the Nanda Devi massif rockslide and the debris flow on a CubeSat image at 10:30 IST, just before the flood reached the Tapovan Hydropower Project site 22km downstream. The dotted black line shows the sediment deposited on the adjacent slopes of the river valley, with the rockslide marked in red. Image: ICIMOD</figcaption></figure>More than a month after the catastrophic flashflood in Chamoli district of the Indian Himalaya, scientists say that the cause was failure of a rock face, and not just the result of a glacial lake burst caused by climate change.Early reports had suggested that the flood of water and debris that raced down the Rishiganga on 7 February, damaging four hydroelectric plants and killing more than 200 people, may have been caused by a glacial lake outburst flood (GLOF). <img width="640" height="463" src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221110111152/636cd8549c7e80680e092e38jpeg.jpg" alt="">However, analysis of satellite images before and after the disaster show that there were no lakes on the Ronti Glacier in the Nanda Devi (7,816m) massif, and the disaster happened in winter when the supra-glacial ponds were frozen. <figure><img width="2048" height="1449" src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221110111152/636cd8569c7e80680e092e39jpeg.jpg" alt=""><figcaption> </figcaption></figure>Scientists have concluded that a 500m wide section of the face of Ronti Peak broke off at 10:30am on 7 February at an elevation of 5,500m and fell with tremendous force on the glacier below. The kinetic energy of an estimated 22 million cubic metres of falling rock also melted ice deposits from a previous avalanche in 2016.Scientists say that the disaster was not directly caused by global warming, but <a href="https://www.carbonbrief.org/factcheck-did-climate-change-contribute-to-indias-catastrophic-glacial-flood" data-saferedirecturl="https://www.google.com/url?q=https://www.carbonbrief.org/factcheck-did-climate-change-contribute-to-indias-catastrophic-glacial-flood&amp;source=gmail&amp;ust=1615627463312000&amp;usg=AFQjCNFgdSlP7mXxpGofYUH2Q6dgxNd1xw">climate change could have contributed</a>. Uttarakhand state recorded its warmest January in six decades this year, and there had been winter storms the previous week that had deposited a lot of snow on the slopes. Ice also cements rock fissures at higher elevations, and when it melts the rocks can come loose.‘The Chamoli flood was not caused by a GLOF as there were no significant glacial lakes in the area,’ write a group of researchers led by Arun B Shrestha in a recent paper for the Kathmandu-based International Centre for Integrated Mountain Development (ICIMOD),  ‘… (but) the <a href="https://www.carbonbrief.org/factcheck-did-climate-change-contribute-to-indias-catastrophic-glacial-flood" data-saferedirecturl="https://www.google.com/url?q=https://www.carbonbrief.org/factcheck-did-climate-change-contribute-to-indias-catastrophic-glacial-flood&amp;source=gmail&amp;ust=1615627463312000&amp;usg=AFQjCNFgdSlP7mXxpGofYUH2Q6dgxNd1xw">increased thaw-freeze cycle of permafrost could have partially contributed to the event.’</a>Even so, researchers at the <a href="https://www.hindustantimes.com/india-news/uttarakhand-underground-glacial-lake-led-to-flash-floods-says-iisc-analysis-101612842535639.html" data-saferedirecturl="https://www.google.com/url?q=https://www.hindustantimes.com/india-news/uttarakhand-underground-glacial-lake-led-to-flash-floods-says-iisc-analysis-101612842535639.html&amp;source=gmail&amp;ust=1615627463312000&amp;usg=AFQjCNHUxxKYGuO-LH5Lmhia8nvW3Oi2HA">Divecha Centre for Climate Change at Indian Institute of Science in Bengaluru</a> used glacier thickness mapper data to detect a sub-surface lake containing 4.5 million cubic metres of water stored in a bedrock depression near the Nanda Devi Glacier terminus that could have caused the flood.  Scientists note that not all Himalayan hazards can be attributed to the climate crisis. An <a href="http://archive.nepalitimes.com/article/nation/Anatom-of-a-Himalayan-tsunami,1330" data-saferedirecturl="https://www.google.com/url?q=http://archive.nepalitimes.com/article/nation/Anatom-of-a-Himalayan-tsunami,1330&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNEsZOhcMFA8vxHbbwUxFh8HOESRwQ">identical rock slip on Annapurna IV</a> in Nepal on 5 May 2012 caused a flashflood on the Seti River that killed at least 72 people. The <a href="https://www.nepalitimes.com/banner/the-courage-and-endurance-of-the-langtangpa/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/banner/the-courage-and-endurance-of-the-langtangpa/&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNHonfzkoR0q5xry76GBTl4UyM05-w">deadly avalanche on Langtang</a> on 25 April 2015 killed nearly 200 people, and was triggered by an earthquake. Another flood that blocked the Arun River in eastern Nepal in July 2017 was traced to a <a href="https://www.nepalitimes.com/editorial/more-himalayan-tsunamis/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/editorial/more-himalayan-tsunamis/&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNFvsIDn5dmC06mGMdSJ_ogC8tBCYg">rock-fall that caused a glacial lake to top over.</a> <figure><img width="850" height="478" src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221110111152/636cd8599c7e80680e092e3ajpeg.jpg" alt=""><figcaption> </figcaption></figure><a href="https://www.nepalitimes.com/here-now/nepals-glacial-lakes-in-danger-of-bursting/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/here-now/nepals-glacial-lakes-in-danger-of-bursting/&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNFTEiergMkJv8bcv86ZOG8uUmM3_Q">GLOFs</a> happen when ice and snow melted by the climate thaw accumulates in enlarging lakes, which can burst due to increased water pressure, or when avalanches fall into them.  And while there are frequent GLOFs, especially in the eastern Himalaya, scientists agree that it was not the main trigger of the Nanda Devi disaster last month.  The other disasters on Himalayan rivers are caused by <a href="https://www.nepalitimes.com/editorial/more-himalayan-tsunamis/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/editorial/more-himalayan-tsunamis/&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNFvsIDn5dmC06mGMdSJ_ogC8tBCYg">bishyari</a>, a local word that refers to a floods due to a landslide blocking a river to impound a lake that suddenly bursts, as what happened in <a href="http://archive.nepalitimes.com/article/nation/One-month-after-the-mountain-fell,1637" data-saferedirecturl="https://www.google.com/url?q=http://archive.nepalitimes.com/article/nation/One-month-after-the-mountain-fell,1637&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNEpOyzNu1-11qUQhioHciDTUNZdGQ">Jure of Sindhupalchok on 2 August 2014.</a>Another catastrophic example is the co-seismic mountain slide that blocked the Seti River about 500 years ago, creating a huge lake that then burst depositing the 200m thick sediment layers on which the city of Pokhara is now located.   Nepal’s former water resource minister and hydropower expert Dipak Gyawali says that bishyari are known to happen in 10-15 year cycles in Nepal. The etymology of the word itself shows that human dwellers of the Himalaya have known of the phenomenon for thousands of years, he says.“Even if these floods are not directly caused by climate change, it can exacerbate the disaster because of extreme weather events,” Gyawali said in an interview.Himalayan floods therefore pre-date climate change, and are caused by the vulnerability of these young, fragile mountains to natural and human-induced processes like the indiscriminate use of heavy earth-moving vehicles on poorly-engineered roads.  Such ‘bulldozer terrorism’, has exacerbated the frequency of landslides in central Nepal  after the 2015 earthquake, according to a recently published paper in the journal, <a href="https://www.sciencedirect.com/science/article/pii/S2590061721000193" data-saferedirecturl="https://www.google.com/url?q=https://www.sciencedirect.com/science/article/pii/S2590061721000193&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNFfGOeUwHuVmX29jd0yc9zjQ9LTRg">Progress in Disaster Science.</a> <figure><img width="499" height="397" src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221110111152/636cd85d9c7e80680e092e3bjpeg.jpg" alt=""><figcaption> </figcaption></figure>After analysing remote sensing data, the researchers conclude that although the number of landslides had started falling after 2015, there has been an uptick since 2017 possibly due to the <a href="https://www.nepalitimes.com/opinion/dozers-and-nepals-development/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/opinion/dozers-and-nepals-development/&amp;source=gmail&amp;ust=1615627463313000&amp;usg=AFQjCNEh-pzzDl7j405T7swUxTKR34tVPg">proliferation of rural road construction</a> around the time of the elections. (See graph, above.) Gyawali suggests that a solution could be better-planned infrastructure and settlements that take into account known hazards. As the Chamoli flood showed, expensive hydroelectric projects located closer to the high mountains are more at risk. He suggests investing in smaller hydropower plants in side tributaries rather than the main stem of major Himalayan rivers to mitigate the danger, and to spread the risk. However, most of Nepal’s planned large hydropower projects are on rivers like the Tamor, Arun, Dudh Kosi, Bhote Kosi and Budi Gandaki. The Himalaya is a young and unstable mountain range that is battered by a heavy monsoon three months a year. Into this high-risk zone, there is now the added threat of climate-induced disasters. Says Gyawali: “We cannot completely remove these disasters from happening, but we can try to understand them and plan to minimise the risk.”

Non-climate cause of Nanda Devi flood

<figure><img width="1859" height="1000" src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/20221110101156/636ccac69c7e80680e08bb88jpeg.jpg" alt=""/><figcaption>What remains of the Dhauliganga hydropower project in Chamoli district of India’s Uttarakhand state after Sunday’s deadly glacial flood. Photo: STR</figcaption></figure>The devastating <a href="https://theprint.in/science/uttarakhand-chamoli-disaster-likely-caused-by-landslide-not-glacial-outburst-satellite-images-reveal/600859/" target="_blank" rel="noopener noreferrer">collapse of the Nanda Devi glacier</a> in India’s Uttarakhand state on 7 February that killed hundreds should be a warning for Nepal to be prepared for similar disasters in future.
A <a href="https://www.planet.com/" target="_blank" rel="noopener noreferrer">PlanetLabs</a> image seems to confirm that a rock-ice slope detached completely from near the summit of the 7,816m high peak in the Garhwal Himalaya near Nepal’s western border, crashed on to the glacier below, and bulldozed the ice and debris into the Dhauliganga and the Alkananda Rivers.
There are tell-tale signs of new brown dust on the western side of the valley in satellite images. The ice melted as it reached a warmer, lower altitude and unleashed the flood that raced downstream. Two hydroelectric projects on the rivers were completely destroyed, highways were washed away and settlements buried under metres of water and debris. 
The Nanda Devi disaster is almost identical to the <a href="http://archive.nepalitimes.com/article/nation/Anatom-of-a-Himalayan-tsunami,1330" target="_blank" rel="noopener noreferrer">Seti River flash flood</a> of 2012 north of Pokhara that killed nearly 80 people. A massive chunk of rock near the summit of Annapurna IV broke off, fell on the glacier and the ensuing flood <a href="http://archive.nepalitimes.com/news.php?id=19479#.YCEipy8RoWo" target="_blank" rel="noopener noreferrer">barrelled down the Set</a>i, causing the fatalities.
Another <a href="https://nepalitimes.atavist.com/high-water" target="_blank" rel="noopener noreferrer">flash flood on the Arun River</a> in eastern Nepal in 2017 was traced to slope failure on a mountain on the Nepal-China border that fell on a glacial lake, triggering a flash flood that washed down so much debris that it dammed the main river.
In all three cases, disasters that at first thought to be a Glacial Lake Outburst Floods (GLOF) turned out to be rock-ice avalanches that led to a glacier collapse. The water and debris then cascaded down the valleys in a deadly paste obliterating everything in its path.
Whereas the increased risk of GLOFs in the Himalaya is linked directly to the climate crisis melting the ice and expanding moraine-impounded lakes, this does not appear to be the direct cause of the Nanda Devi event—just as it was not in the Seti and Arun. Rockfalls that lead to the collapse of glaciers, squeezing the water out of ponds in them and melting of the ice as it is pushed down to a warmer altitude.
Some of these glaciers may have lakes that top over when an avalanche or rockfall hit their surface, or global warming may have melted the ice within debris-covered glaciers. We do not know if these events are becoming more frequent due to a Himalayan thaw caused by the climate crisis.
Whatever the case, it is clear that the countries that share the Himalaya from Afghanistan to Burma have to be prepared for more frequent disasters of this type. The risk of GLOFs and flash floods have to be <a href="https://www.nepalitimes.com/banner/human-face-of-a-himalayan-climate-crisis/" target="_blank" rel="noopener noreferrer">factored into planning infrastructure</a> and human settlements downstream.
Although GLOFs and glacial collapse get all the attention, the Himalaya are also prone to landslide-blocked dams during the rainy season. The mountains are relatively young, they are seismically active and their slopes very unstable. Monsoon rains have been known to trigger landslides the block major rivers, as happened on the Bhote Kosi in Jure in 2014.
Fortunately, the river found a way around the blockage. But there have been cases when the impounded lake is large enough to cause catastrophic bishyari floods downstream when the landslide dams collapse.
The flat terraces where the city of Pokhara is situated today was probably formed, geologists say, when a landslide blocked the Seti upstream some 700 years ago. It gave way, <a href="http://archive.nepalitimes.com/blogs/kundadixit/2012/05/05/avalanche-flood-on-seti/" target="_blank" rel="noopener noreferrer">unleashing a tsunami</a> at least 150m high. Pokhara is located in the debris fan of this flood which dammed side rivers, forming Phewa, Begnas and other lakes.
To warn that <a href="https://www.nepalitimes.com/banner/tracing-past-glacial-floods-in-kangchenjunga/" target="_blank" rel="noopener noreferrer">similar catastrophes can strike</a> in the Himalaya is not panic-mongering. It is a call to be prepared. And let us hope the worst-case scenario of a mega-quake causing multiple glacial lake outburst floods does not happen any time soon.A Himalayan <a href="https://www.nepalitimes.com/here-now/nepals-glacial-lakes-in-danger-of-bursting/" target="_blank" rel="noopener noreferrer">Glacial Lake Inventory</a> launched at a <a href="https://www.icimod.org/event/glacial-lake-inventory-launch/" target="_blank" rel="noopener noreferrer">webinar</a> on Monday says that of the expanding glacial lakes in the Himalaya, 47 on the watersheds of Nepal’s three main rivers are at high risk of bursting, and causing catastrophic floods downstream. Of these, 42 lakes are on the Kosi River basin in eastern Nepal, three are on the Gandaki and two on the Karnali watersheds.A report last year by the <a href="https://www.icimod.org/event/glacial-lake-inventory-launch/" target="_blank" rel="noopener noreferrer">International Centre for Integrated Mountain Development (ICIMOD)</a> and UNDP mapped 3,624 glacial lakes in the Kosi, Gandaki and Karnali basins and found 47 lakes at risk from bursting. Of these 25 are in Tibet and drain into rivers that flow into Nepal. For now, existing towns along the rivers must have early warning systems. Infrastructure planning must take into account the glacial flood risk. And because so many of the high-risk glacier-fed rivers flow across national boundaries, international cooperation must be a must.

More Himalayan tsunamis

<figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/2022110915114/636bb3aa9c7e80680e07bb55jpeg.jpg" alt="" width="1148" height="759"/><figcaption>Tso Rolpa glacial lake at 4,580m has grown seven times in size in the past 60 years due to global heating. Photo: RASTRARAJ BHANDARI</figcaption></figure>A new report out this week warns that hundreds of glacial lakes in the Himalaya are in danger of bursting because global heating is melting the ice on the world's highest mountains. However, on only two of them have there been mitigation measures to reduce water levels.Those projects have been prohibitively expensive, and questions have been raised about their sustainability and whether they offer a long-term solution.The water level of the <a href="https://www.nepalitimes.com/banner/human-face-of-a-himalayan-climate-crisis/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/banner/human-face-of-a-himalayan-climate-crisis/&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNHQqRLDTM5grtmwzGwIaNowvT8YVA">Tso Rolpa glacial lake in the Rolwaling Valley</a> was lowered 20 years ago after scientists warned that it was in imminent danger of bursting. The project cost $9 million at the time, most of it coming from The Netherlands.Its sluice gate lowered the water level by only 3m, and scientists now say it needs to go down by a further 20m to reduce risk of it bursting. A network of early warning stations downstream also has not functioned as planned.<figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/2022110915114/636bb3ad9c7e80680e07bb56jpeg.jpg" alt="" width="749" height="500"><figcaption> </figcaption></figure>The other project was a <a href="https://archive.nepalitimes.com/article/from-nepali-press/Diverting-danger,3172" data-saferedirecturl="https://www.google.com/url?q=https://archive.nepalitimes.com/article/from-nepali-press/Diverting-danger,3172&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNEzjK6xZYP2UlpO845JQUGvWXX7-w">drainage channel and gate built on Imja Lake</a> in the Mt Everest region in 2016 by the Nepal Army with support from the United Nations Development Programme (UNDP) and the Global Environment Facility (GEF) at a <a href="https://undp-climate.exposure.co/in-pictures-peoplepowered-climate-adaptation-in-nepal" data-saferedirecturl="https://www.google.com/url?q=https://undp-climate.exposure.co/in-pictures-peoplepowered-climate-adaptation-in-nepal&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNH3t2JWDSs3D2O1Qt4izuTV31jEpQ">cost of $7.2 million</a>.The project located at 5,000m altitude was <a href="https://archive.nepalitimes.com/article/Nepali-Times-Buzz/Sustainable-Mountain-Development-Getting-the-Facts-Right-Jack-D-Ives,946" data-saferedirecturl="https://www.google.com/url?q=https://archive.nepalitimes.com/article/Nepali-Times-Buzz/Sustainable-Mountain-Development-Getting-the-Facts-Right-Jack-D-Ives,946&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNE-VqTq7lypmtE-h7cavGE15lDCpw">criticised at the time</a> for being an expensive show-case on a popular tourist site near Mt Everest, and for wasting money on a lake that is relatively stable because it is buttressed by two side moraines of the Lhotse Nup and Nuptse Glaciers. Glacial lakes like <a href="https://digitalcommons.macalester.edu/cgi/viewcontent.cgi?article=2306&amp;context=himalaya" data-saferedirecturl="https://www.google.com/url?q=https://digitalcommons.macalester.edu/cgi/viewcontent.cgi?article%3D2306%26context%3Dhimalaya&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNGiefBPIhM8TyxKAWYVSeHxZbPX6Q">Thulagi in Lamjung</a> on the <a href="https://archive.nepalitimes.com/page/lake-464-glacial-lake" data-saferedirecturl="https://www.google.com/url?q=https://archive.nepalitimes.com/page/lake-464-glacial-lake&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNE1Mutd985NNyrTLmT_nvWOtHNhYQ">Hongu basin</a> were said to be in much greater danger of bursting, and <a href="https://glacierhub.org/2016/06/22/military-intervention-at-nepals-fastest-growing-glacial-lake/" data-saferedirecturl="https://www.google.com/url?q=https://glacierhub.org/2016/06/22/military-intervention-at-nepals-fastest-growing-glacial-lake/&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNEMww2bKHDexG28W6Fcyj4fKtuDWg">needed more urgent mitigation</a>.<figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/2022110915114/636bb3af9c7e80680e07bb57jpeg.jpg" alt="" width="537" height="431"><figcaption> </figcaption></figure>And it has emerged that four years after the project was completed and the water in Imja Lake lowered by 3.4m, the Nepal Army and its main contractor have yet to remove their excavators and other equipment from the site as per the contract -- flouting guidelines of Sagarmatha National Park, which is a World Heritage Site.Despite recent interventions by UNESCO and the national park, the Nepal Army has said it is technically not possible to take the equipment out because of altitude restrictions on its helicopters. The firm hired by the army, Krishna Construction, says its contract does not say anything about removal of equipment.<img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/2022110915114/636bb3b19c7e80680e07bb58jpeg.jpg" alt="" width="536" height="458"><figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/2022110915114/636bb3b39c7e80680e07bb59jpeg.jpg" alt="" width="540" height="330"><figcaption> </figcaption></figure>The Glacial Lake Inventory report launched at a <a href="https://www.icimod.org/event/glacial-lake-inventory-launch/" data-saferedirecturl="https://www.google.com/url?q=https://www.icimod.org/event/glacial-lake-inventory-launch/&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNFp2v-R1EwAEPQAwzlTD_C-dgl5Pg">webinar</a> on Monday says that of the expanding glacial lakes in the Himalaya, 47 on the watersheds of Nepal’s three main rivers are at high risk of bursting, and causing catastrophic floods downstream. Of these, 42 lakes are on the Kosi River basin in eastern Nepal, three are on the Gandaki and two on the Karnali watersheds.However, not all the lakes are located in Nepal. Of the 47 dangerous lakes, 25 are in Tibet and empty into rivers that flow down directly into Nepal. One of the high risk lakes is in Indian territory near Karnali.This week’s report by the Kathmandu-based <a href="https://www.icimod.org/event/glacial-lake-inventory-launch/" data-saferedirecturl="https://www.google.com/url?q=https://www.icimod.org/event/glacial-lake-inventory-launch/&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNFp2v-R1EwAEPQAwzlTD_C-dgl5Pg">International Centre for Integrated Mountain Development (ICIMOD)</a> and UNDP mapped 3,624 glacial lakes in the three river basins in Nepal, China and India, of which 2,070 are within Nepal’s boundaries. The other 1,509 are on the Tibetan Plateau in China and 45 are in India, but drain into Nepal.The researchers evaluated the risk factors for the glacial lakes depending on the integrity of their moraine dams, topography of the surroundings and the risk of avalanche into the lakes, as well as downstream settlements and infrastructure and divided them into three categories.Of the 47 dangerous lakes on the Kosi, Gandaki and Karnali basins, 31 were found to be at very high risk of bursting and causing damage. Twelve other lakes are at moderate risk and there are four lakes in the lower risk category.<figure><img src="https://superdesk-pro-c.s3.amazonaws.com/sd-nepalitimes/2022110915114/636bb3b49c7e80680e07bb5ajpeg.jpg" alt="" width="1500" height="831"><figcaption> </figcaption></figure>The lakes are expanding because the ice fields feeding them are <a href="https://www.nepalitimes.com/banner/on-thin-ice-in-the-khumbu/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/banner/on-thin-ice-in-the-khumbu/&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNFziTwdDLkl5JF1xIjm8fDL18A4Sw">melting faster due to global heating,</a> as well as increased deposition of soot particles on the snow. <a href="https://www.nepalitimes.com/banner/a-terrifying-assessment-of-himalayan-melting/" data-saferedirecturl="https://www.google.com/url?q=https://www.nepalitimes.com/banner/a-terrifying-assessment-of-himalayan-melting/&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNFEwtJkUB1QL98Dmfr7jVG349bG3Q">An ICIMOD assessment</a> last year reported that even in the best case scenario, the Himalaya will lose one-third of its ice and snow during this century. But recent studies have shown that the melting is actually happening faster than previously thought, and is accelerating.This has increased the number of glacial lakes in the Nepal Himalaya as well as their sizes. For example, remote sensing data in the report showed that there were 3,609 glacial lakes in Nepal’s three river basins with a combined area of 180sq km. By 2015, the number had grown to 3,696 and they covered a combined area of 195.4sq km.Scientists have long noted that the rate of melting is higher in the eastern Himalaya than in the west, and the report confirms this. Interestingly, while the number of glacial lakes in the Kosi basin has gone down, their total area has increased by 14sq km – largely because supraglacial ponds have merged, or the lakes have drained without bursting.The report has also recorded 26 <a href="https://nepalitimes.atavist.com/high-water" data-saferedirecturl="https://www.google.com/url?q=https://nepalitimes.atavist.com/high-water&amp;source=gmail&amp;ust=1599636709453000&amp;usg=AFQjCNG57P3tY-Tj18gLSJl0V0eJT_JiAg">glacial lake outburst flood (GLOF) events</a> in the Nepal Himalaya since 1977, but only 14 of them were on lakes located in Nepal. This emphasises the importance of trans-boundary early warning system – especially on lakes in Tibet upstream on the two Bhote Kosi rivers, Tama Kosi, the Arun and others.

glacial-lakes

For destruction, ice is also great and will suffice

DANGER: Nepal’s glacial lakes are filling up

Non-climate cause of Nanda Devi flood

More Himalayan tsunamis

Nepal's glacial lakes in danger of bursting