The devastating flood in Sikkim's Teesta river on the night between October 3 and 4, 2023 caused by an outburst in a glacial lake, about 120 km from capital Gangtok in northern Sikkim,  though primarily caused by nature, human neglect, particularly that of government functionaries, also did not play any less insignificant role in multiplying the tragedy.  The lake, called  South Lhonak, situated at an altitude of about 17,000 feet ( over 5100 metres) above sea level. Interestingly, South Lhonak is not even the primary source of the mighty river.

The primary source of Teesta river is a river called Tso Lamhu which is fed by ice waters from Sikkim's largest glacier called Zemu at India's highest and world's third highest mountain Kanchendgonza worshipped as God by a section of the local population. Zemu is 26 km long with same surface area as average width is 1 km

Other nearby glaciers which also empty in Tso Lhamu glacial lake and thus contribute to Teesta are Kangtse and Pauhunri. Another stream originates from South Lhonak glacial lake and joins Teesta few kilometres downstream in north Sikkim itself. It is the outburst of an embankment at South Lhonak lake and possible cloudburst and unusually heavy rainfall which led led to sudden flow of large quantity of water in Teesta and thus to huge loss of life and property along the entire  course of the Teesta river.

Nature exacts revenge
 
Glacial lakes are fed by melting glacier ice. Continuous and accelerated receding of glaciers mainly due to global warming always poses a big threat of flooding due to the rupture of surrounding hills caused by ever-increasing pressure of water and ice when the volume of water and ice goes beyond the tolerance of surrounding hills. All such lakes all over the world need constant and competent monitoring to ensure that there is no sudden rupture resulting in the sudden release of a disproportionate quantity of water downstream. This well-known phenomenon is called GLOF-- Glacial Lake Outburst Flood.

This is what happened on October 3-4 at South Lhonak. The state government did in fact foresee this eventuality almost 10-12 years before the accident and acting on sane scientific advice had  taken steps to avoid such an eventuality.  But that is where the government's proactive action stopped and apathy set in. May be the very high altitude and difficult terrain which is just 4 km from the Tibet border was also one reason for the project being shelved. 

On September 18,2011 a devastating earthquake of 6.9 intensity on Richter  scale with epicenter close to Nepal-Sikkim border  on Kanchendgona ranges had hit Sikkim. After the earthquake, the central government commissioned its scientific arm called C-DAC (Centre for Development of Advanced Computing) to study the problem and come out with an appropriate solution. A team of C-DAC scientists 
   along with state government  officers visited Sikkim's two  glacial lakes-- Lhonak and Sakho Cho in May 2012. The team's  subsequent report along with data analysis of satellite imagery warned about a likely future  episode of GLOF as finally happened on night of October 3/4, 2023. To meet the threat, the government agencies installed indigenous early warning systems  (EWS), first on Shakho Lake in July 2013 and later in September 2016 on Lhonak  Chho.Both the sensor systems worked for just about 6-7 months each and then stopped transmitting data to control  centre through INSAT satellite  which they were designed to and supposed to transmit. Some equipment was vandalized and even stolen. But probably since no "incident" (euphemism for tragedy) had so far occurred for the last 11-12 years, the decision makers put the matter on the back burner. On October 3-4  nature extracted its revenge and large number of human life and property were washed away in minutes and hours causing untold devastation in this northeastern state bordering China.

Need for cost-benefit analysis 

Sikkim's biggest hydropower generation plant is located near  a town called Tsungthan in North Sikkim. The owners claimed that sluice gates of dam could not be opened in time as warning regarding  GLOF was received from Indo-Tibetan Border Police less than 15 minutes before the icy waters crashed into the dam. The small  town of 2200 people was inundated in few minutes, the power plant was destroyed as the dam breached. The company owning the power plant-- a joint venture  called Teesta Urja  with the state government - has claimed that they have incurred financial losses to the tune of about Rs 11000 crores. Other habitations which suffered loss of life and property are Singtam Bazar, about 27 km from Gangtok and Rangpo  (both in Sikkim) and Kalimpong in West Bengal and areas on river bank further down. The Teesta runs a course of about 414 km in Sikkim and West Bengal before entering Bangladesh where it joins the Brahmaputra before finally emptying into the Bay of Bengal. Most power generation plants on Teesta have suffered massive destruction and are presently shut down.

Sikkim's total hydro power potential has been projected to be about 8000 MW. Presently only about 3000 MW has been installed, mostly on the Teesta. Several new plants are at various stages of implementation. Since India is still power deficient and needs to plan for many more projects in all areas of power generation-- hydro, wind, thermal, solar and nuclear--one accident like this cannot and should not deter it. But all concerned agencies carrying  out ecological  studies, technical suitability, fragile nature of our hills have to do their work diligently and scrupulously through experts. There will always be elements trying to profiteer from such big projects through corruption and nepotism. Therefore, the maximum responsibility will lie with decision makers/ political leadership that ulterior considerations or favoritism do not enter into final decision making of such critical projects. 

 In the Himalayas about 87 hydroelectric plants are already operational. Another 30 are under various stages of implementation. It is imperative that Infrastructural requirements like roads, bridges, tunnels, power plants and other industries should be weighed against their ecological impact by experts and their cost-benefit analysis undertaken before final decisions are taken. The damage done by man to nature can sometimes be irreversible and irredeemable. 

(The writer is a journalist-turned-entrepreneur who has worked for many years in Sikkim. Views are personal.)