GLACIAL LAKE OUTBURST FLOODS (GLOF) The ticking water bombs in the Himalayas

(Dedicated to those people who lost their lives and            properties on the 3^rd & 4^th October 2023)

MK SUBBA

42 Glacial Lakes (GLs) are located in Sikkim out of the 100 GLs that have been identified in the Indian Himalayan Region (IHR), with Jammu & Kashmir and Ladakh having 15 each followed by Himachal Pradesh (10) and Arunachal Pradesh and Uttarakhand having 9 each. The 42 GLs located within Sikkim  are  as shown in the figure 1 below.

Decoding and reading the map of Sikkim figure 1 with the available data inputs as tabulated in figure 2  gives deeper insights and a clear view of the geographical location of these 42 GLs and their current status.

Figure 2

Earlier, the Glacial Lakes were coded with Sikkim state specific codes such as (SK) but now they are denoted with individual twelve digit numbers as columned in LAKE UID/ID  above. Out of the 42 GLs only three are located in West district, indexed as 14 (Tikip Chu), categorized as a very high risk GL, 27 (Bhale Pokhari) and 28 (Lachmi Pokhari), rest all the thirty nine GLs are located in North Sikkim with sixteen GLs categorized as very high risk. The South Lhonak Lake is indexed as 4, and still in the very high-risk level, and close to it is the Green Lake indexed as 31 and the Gurudongmar Lake has been indexed as 22. Most of these GLs are located above  4000m  altitude  in the trans boundary area along the Line of Actual Control with China in the Tibetan Autonomous Region. Lake no 15 and 39 are coded with one single  UID/ID (07478A050208).

Although revered and worshipped, these Glacial Lakes were primarily viewed in Sikkim  as tourist destination, but all that has changed post what Sikkim and the rest of the world witnessed on the 3^rd and 4^th of October 2023, the destruction and mayhem the Glacial Lake Outburst Floods (GLOF) from the South Lhonak Lake  have caused to lives, property and the environment, which Sikkim has fully not recovered and may take years to rebuilt and re-strength live and livelihoods hit by the flash floods of that fateful night.

Well, the truth is what fury death and destruction we witnessed on the 3^rd and 4^th of October 2023 is a serious warning for reaching some definitive policy decision and wide spread public awareness, if Sikkim is to avert and prepare for what we are now exposed to the 42 Glacial Lakes in our surrounding, that too with 17 of them in the very high risk level, as much of the related  information are not easily available in the public domain. These GLs and Water Bodies (WB) located in the Indian Himalayan Region (IHR) covering a geographical area of 5.3 lakh kilometer square and extending over 2500 km in length are the ticking water bombs ready to explode any time due the vagaries of geological  factors especially the climate change accelerating the melting of the glaciers, which Sikkim is home to some 320 odd glaciers that feed these water bodies.

Advance research shows that around 15 million population of China, Pakistan, India and Peru are exposed to high risk  of GLOFs. In India 4% of its population lives in the foothills of the mighty Himalayas. The Himalayas, called the third pole, home to the highest number of glaciers and snow covered area apart from the Arctic and the Antarctic circles being the other poles, is the source and origin of the Indus, Ganga and Brahmaputra, that forms the important river basins system in India effecting and supporting lives and livelihoods across many states in India. The Himalayas is one of the most geologically active regions of our planet as nearly 15% of earthquakes, with magnitude  more than 8 on the Richter scale have hit the Himalayas so far, most importantly, it is the home to numerous glaciers- the source of fresh water on which millions of people depend downstream. It is also the prone to natural calamities due to its fragility and more due to the impact of the climate change causing landslide induced flashfloods, cloudburst and GLOFs. The figure 1 and  figure 3 below shows the satellite remote sensing images  cum mapping of the GLs and WBs, which started in 2009 taken as the base year as these lakes are located in remote hostile terrain which are inaccessible where the hands on approach is not possible, hence its surveillance depends on the state of the art latest remote sensing satellite technology, which India has been adopting through the National Remote Sensing Centre, Hyderabad.

The figure 3  shows the   locations and positions of the  Glacial Lakes and  Water Bodies in the Indian Himalayan Region from Arunachal Pradesh in the east through Bhutan, Sikkim, Nepal, Uttarakhand, Himachal Pradesh till Jammu and Kashmir in the North even covering the Tibetan Autonomous Region of China which forms the river basins of Brahmaputra, Ganga and the Indus   from where the rivers flowing into India originates. Each of these GLs and WBs are coded with state specific individual Lake IDs cum UIDs to follow the progress of the increase or decrease of the water spread area calculated as the difference between the current water spread area  of the lake and the base year (2009 & 2011) and even the average area covered by these lakes in the last 2 years, 5 years and 10 years too. In the year 2009 extending upto 2011, the government of India then started to create the inventory list and started monitoring  of the GLs and WBs having water spread area more than 10 hectare thus recorded 503 GLs and 1525 WBs in the Indian Himalayan Region across India, Bhutan, Nepal, China and Myanmar through which the rivers flowing into India are feed.

This inventory list of 503 GLs and 1525 WBs of the Brahmaputra, Ganga and Indus Basins were prepared measuring their length, breath and area  with the respective elevations coding them with all individual  Lake IDs and UIDs, also it is found that 50% of these GLs and WBs were located within the elevation of 4000m to 5000m. Thus the  GLs in Sikkim were coded in the series of (SK) series The South Lhonak GL   Lake ID cum UID no. SK-20/ 03-78A-014, but now coded with new UID/ID (07478A010059) as shown if figure 2. Similarly, the 42 GLs in Sikkim have been re-coded with the twelve digit numbers as of now as shown in table figure 2.

Figure:3

In the year 2015, 16 GLs and WBs having more than 50 hectares  were prioritize for study taking considering their locations and vulnerability to the human settlements and hydro projects downstream and thus five GLs including the South Lhonak Lake,  situated in Sikkim where amongst the  short listed for  study, on top priority.  Thus in the year 2015, an advisory sheet, “ Glacial Lake Outburst Flood-South Lhonak System in Teesta River Basin”, was prepared by the government of India focusing on the South Lhonak Lake and the three other GLs located above it, namely, which where the other tributaries of the Teesta as these GLs were considered to be the critical lakes, hence found necessary to analyze and study the impact of an imminent GLOF to all the human settlements of Lachen, Chungthang, Mangan, Dikchu, Singtam, Manipal Mazitar and Rangpo and the Hydro Power Projects, Teesta stage I, II, III IV, V and Teesta Low  Dam  III and IV at Bara Munga in West Bengal  all   located downstream, which stood to  be vulnerable in case of the outburst of these GLs.

The maximum size of the water spread area of the South Lhonak Lake recorded was 136 (ha)  in the month  of June 2009. All possible scenarios of different types of permutations  and combinations of the possible GLs outburst were taken into consideration as also two of the Lakes were interconnected. Thus the all the worst case scenarios of only South Lhonak Lake   bursting or only other three Lakes bursting separately lake and any of the two lakes bursting together and finally all four Lakes bursting together were taken into consideration and thus the  hazard modeling and mapping for the South Lhonak Lake flow path, velocity and preliminary hazard classification along with event intensity were released accordingly. The study adhered to some assumptions and limitations, most importantly, that the flow is not modified at the hydro power projects downstream, went completely wrong as the Teesta stage III at Chungthang  and Teesta stage V at Dikchu totally collapsed due to the impact of the GLOF on the fateful night of 3^rd and 4^th October 2023.

Secondly, that the flow of the river assumed at 1000 meter cube per second too changed abruptly as the voluminous water stored by the Dams too added to the increased flow downstream when the Dams collapsed, causing  maximum damage as  1423 houses were completely damaged 579 houses were partially damaged leaving 102 people dead and 76 missing effecting the lives of 88,400 of the population of Sikkim and also that of West Bengal too as the Teesta covers a flow length of 150 km within Sikkim and  123 km in West Bengal and another 140 km in Bangladesh, till it merges into the Bay of Bengal. The Teesta river course intercepted by now, the damaged Teesta stage III Dam (Sikkim Urja Ltd.) at Chungthang, the Teesta V Dam at Dikchu and the Teesta VI Barrage at Sirwani, Singtam followed by two Lower Dams and  Gojaldoba Barrage, all three projects, within West Bengal as shown in figure 1.

All these catastrophic flash flood death and destruction happened only  when the limited scenario of the single GL, the  South Lhonak lake bursting but still  believed to be one of the worst climate related disasters as reported by ‘The State of the Climate Asia 2023’ as the  spread area of the South Lhonak lake reduced drastically  from 171 hectares as on 23^rd of September 2023  to 130  hectares on October 5^th  2023. But surprisingly, the data set of the South Lhonak Lake shows that there was a similar voluminous  discharge from the Lake in the year 2016-17, when the Lake recorded water spread area of 128 hectares in August 2016 which suddenly dropped to 99 hectares on September 2016, but no flash flood of any destructive magnitude has been observed. As of date the South Lhonak Lake has again refilled to 136 hectares size again and continuous to be in the very high risk level. Further tracking the water spread area of South Lhonak Lake, it increased by 65.96% in June 2019 when it expanded to 156 hectares and an advisory of the lake requiring continuous monitoring  was issued.

Again reference to figure 1 and 2 above, clearly Sikkim is facing very potent and imminent threat from these 42 Glacial Lakes, which are the ticking water bombs ready to explode nestled high up in the Indian Himalayan Region, worst still, its information and progressive report is not privy to public at large. As per the Geological Survey of India, there are  9,575 glaciers in the IHR and Sikkim is home to 320 glaciers.   As is evident that the glaciers around the world have started to melt at an alarming rate now primarily because of human lifestyle  and industrial pollution increase in emission of greenhouse gases with rapid increase of temperatures and thus the resultant global warming and climate change. Sikkim too records that there is a gradual rise of temperature at the rate of 0.2 to 0.3 degree centigrade per decade with unseasonal heavy rainfall and much warmer and drier winters too.

Thus the  glacial melt will not only pose the threat of GLOFs but will ultimately change the weather pattern, impacting industrial output  socio-economic condition and agriculture pattern in  Sikkim. All the 42 GLs out flow discharge are the tributaries of the river Teesta and hence before we resume our livelihood and economic and industrial settlement along the Teesta basin yet again, firstly the carrying capacity of the Teesta basin  has to be reassessed and re-visit the report approved by the  MoEFCC, GoI in 2007, for any  planned and sustainable future for Sikkim.

Secondly, already the National Disaster Management Plan 2019, has categorized the Indian Himalayan Region including the North-East region, with its peculiar topography, geology, climate and environment along socio-cultural tradition as a priority sector requiring specific disaster mitigation and containments plans. The Disaster Management Plan 2019, has listed GLOFs as a hazard and a disaster under  natural calamity and worst still, within the Sikkim Himalayan Region many GLs are still in the process of formation.  The mitigation, management and containment of any disaster requires  a well coordinated multi level inter-ministerial and inter-agency from local to Centre level to establish the required network in the hour of crisis.

Thus the National Disaster Management Authority (NDMA) has laid down specific guidelines for the management of GLOFs with a shared responsibilities between the concerned state and the Centre. In understanding the risk of GLOFs, the role of the State is to involve the local communities in monitoring the GLs and WBs and data collection and most importantly to install the appropriate warning system, mapping the unsafe areas and settlements, amalgamate the indigenous knowledge and hazard zonation. While the Centre, has to provide the technical support, monitoring, research along with understanding the GLOF risk in relation to the people and property located downstream and the Dam break modelling and downstream vulnerability assessment.

Above all, the Centre has manage the effective coordination and seamless communication between the central and the state agencies to ensure quick, clear, effective dissemination of warnings, information and data and the State is tasked with the all important responsibility of preparation and implementation of the disaster management  plans with State specific strategies and make legal provisions mandating infrastructure developers, especially private hydropower developers to engage in GLOF early warning and risk reduction activities. Also the State is tasked with the responsibility of amending town and city plans to reduce risks, enhance the capacities of Panchayat Raj Institutions and local communities at risk to monitor and prepare for the likelihood of GLOF. But all these are only in the rule book as usual.

 Nevertheless, post the Sikkim disaster, the Centre government on the 20^th of November 2023 has constituted a high level committee to examine the effect of GLOFs in Teesta River projects and Sikkim disaster, headed by Sh. R.K. Jain, Ex-Chairman , CWC along with nine other members as per the clause(8) of schedule II of the Dam Safety Act, 2021, with reference to some important Terms of Reference as (1) to examine the causes leading to the bursting of south Lhonak Glacial lake and consequent failure of Teesta-III dam and damages to other downstream dams and interact with the dam owners/agencies on the same point of reference (2) To examine the status of the Early Warning System installed by the dam owners in Teesta basin and its performance during the GLOF disaster (3) to  review the status of the Glacial lakes, including the frequency of monitoring and responsibility of the dam owners (4) To review the action taken by Sikkim state and dam owners following the issuance of CWC advisory on GLOF in 2015 to the Sikkim state (5) To review the reservoir  and gate operations carried out by the dam authorities during the heavy discharge release.(6)To recommend measures to prevent/minimize the recurrence of such events in future.

The committee was to submit its report within two months. Parallelly, the Sikkim govt. too on the 11^th of September   constituted one High Level Steering Committee (HLSC) headed by the Chief Secretary along with the DGP, Sikkim Police and eight others as members with the Terms of Reference as to coordinate with the defense establishments, paramilitary forces and the Central Government agencies to provide support, to partner with leading experts and organizations , to evaluate various mitigation options and approve the glacial flood mitigation plans and to suggest possible funding source  to support the glacial floods mitigation plans. The HLSC was to meet at least once in six months. The HLSC was followed by another formation of Multi-disciplinary Task Force (MTF), headed by the Secretary, Science and Technology Department and nine other members. The terms of Reference of the MTF was to contribute to the expeditions to the high risk Glacial lakes, prepare mitigation plans for the same, invite subject experts, regularly update the HLSC  on progress made and future plans. The MTF was to hold meeting at least once in a month.

The Centre has on the 25^th of July 2024 approved Rs 150 crore under The National Glacial Lake Outburst Floods Risk Mitigation Programme  to mitigate the risks from the 189 high risk GLs and WBs in the states of Himachal Pradesh, Uttarakhand, Sikkim and Arunachal Pradesh and on the  1^st of August 2024, The Disaster Management( Amendment) Bill 2024 was introduced in the Lok Sabha on the  to strengthen the working of the National Disaster Management Authority and the State Disaster Management Authorities to prepare national and state level plans  along with disaster data base focusing on disaster risk reduction, especially in managing the climate induced disasters. The Bill further incorporates the Urban Disaster Management Authorities to look into the city level disasters for the state capitals and cities that have municipal corporations,  all these amending the two decade old The  Disaster Management Act 2005 on the backdrop of India facing multiple calamities especially climate induced resulting in droughts, cloudbursts causing  landslides and  flash floods, cyclones, heatwaves the  accelerated melting of the glaciers and thus leading to GLOF and outburst of other WBs formed in the  IHR causing massive erosion with increased flooding  engulfing everything on its way downstream causing unprecedented damages to live and properties as witnessed in Sikkim on the 3^rd and 4^th of October 2023.

Sikkim at present, though our Air Quality Index (AQI) in all the eight station from Rangpo to Chungthang records good to satisfactory  and the Water Quality across the 30 stations are within the permissible safe limits, the State is facing the brunt of the effects of climate change and global warming which is here to stay. Nevertheless the State is well equipped with its own specialize, “Sikkim State Climate Change Cell”, established in 2014 under the National Mission for Sustaining the Himalayan Eco-system under National  Action plan on Climate Change, additionally supplemented with the “Sikkim State Remote Sensing Centre” which was engaged in monitoring of the South Lhonak Lake too. Also, the Centre has approved the “Mission Mausam” with an outlay of Rs 2000 crores over the next two years to boost India’s capacity to forecast and mitigate extreme weather events and the impacts of climate change with the deployment of state of the art radars and satellite system and automated real time data sharing technology.

So with all the  multi layered Centre-State (GLOF) disaster management plans supported by specialized expert committee groups at different levels funded by special mission resources, and regular expedition carried out by the Swiss Agency for Development and Cooperation, Sikkim State Disaster Management Authority, National Disaster Management Authority teams and the concerned line department of the government of Sikkim, we only hope that the imminent danger and hazard posed by these 42 Glacial Lakes and other Water Bodies nestled in the Sikkim Himalayan Region, the ticking water bombs, can be mitigated and contained to ensure that Sikkim and the downstream areas remains disaster resilient and safe least similar catastrophic and tragic events of the 3^rd and 4^th of October 2023 doesn’t repeat yet again.

(Views are personal. Email: mksubba@gmail.com)