From Warnings to Waterworks: Siphoning Solutions for Sikkim’s Flash Flood Crisis

In a tragic turn of events, a flash flood from Lhonak Lake in North Sikkim wreaked havoc on October 4, 2023, causing widespread damage downstream. This catastrophe has left at least 11 individuals dead and over 120 missing, highlighting the devastating consequences of ignoring red flags and warnings from government agencies and scientific expeditions.

A Decade of Red Flags

Surprisingly, this disaster did not occur in isolation. Government agencies and scientific expeditions have been sounding the alarm bells regarding the vulnerability of Lhonak Lake to a glacial lake outburst flood (GLOF) for at least a decade. Documents accessed by HT reveal that in 2013, scientists from the National Remote Sensing Centre in Hyderabad issued a stark warning, labeling Lhonak Lake, perched at a daunting altitude of 5,245 meters above sea level, as “highly vulnerable” to a GLOF event. This event had the potential to inflict extensive damage on life and property downstream, including critical infrastructure such as dams and powerhouses.

The Sikkim State Disaster Management Authority (SSDMA) further emphasized this vulnerability in their 2019 report, indicating that townships like Chungthang, Dikchu, Singtam, and Rangpo were at risk, with potential loss of life and property. Numerous field expeditions over the years corroborated the looming threat, with the first one in August 2014 by a team from the Snow and Avalanche Study Establishment (SASE) and Sikkim Department of Science and Technology and Climate Change. This team underscored the potential for “devastation.” It urged the development of a mitigation management plan, including using siphoning as a short-term measure.

The Siphoning Solution

Siphoning, a unique approach to diverting water from a reservoir over an embankment dam, emerged as a potential solution to the impending disaster. An expedition to South Lhonak Lake in September 2016 involved a team from the Sikkim State Disaster Management Authority, the Indo-Tibetan Police Force, and the Students Education and Cultural Movement of Ladakh, led by Sonam Wangchuk. This team concluded that conventional engineering intervention was unfeasible due to the risk posed by melting dead ice.

Subsequently, Wangchuk was appointed as a consultant to implement the siphoning process. This initiative included the installation of high-density polyethylene (HDPE) pipes in three pipelines, each measuring between 130 to 140 meters in length, capable of pumping out water at a rate of 150 liters per second. A sophisticated lake water monitoring system was also implemented, marking India’s first-ever attempt to siphon a glacial lake.

Climate Change and Growing Glacial Lakes

The relentless march of climate change has further exacerbated the situation. The shrinking glaciers and expanding glacial lakes in high-altitude regions have intensified the risk of GLOFs. Sattar, a scientist from the Indian Institute of Science, Bengaluru, reported that the glacier’s size had decreased from 6.4 sq km to 5.1 sq km over the past 29 years. Correspondingly, the lake had expanded from 0.17 sq km in 1977 to 1.35 sq km in 2019. This transformation in the landscape has amplified the potential for disasters like the recent flash floods.

The Triggers of Tragedy

While the exact causes of the flash floods are still under investigation, heavy rains and an avalanche triggered by these rains remain plausible culprits. The avalanche, potentially induced by heavy precipitation, may have struck Lhonak Lake, setting off a GLOF. The surge of water and debris subsequently coursed down the Goma Channel, eventually converging with the Zemu River and the Lachen, a tributary of the Teesta River.

The flash floods devastated the Teesta 3 dam near Chungthang, causing substantial damage to the dam structure and the connecting bridge to the powerhouse. This breach in the dam unleashed a flash flood, compounding the disaster.

Government Response and Ongoing Relief Efforts

In the wake of this tragic event, Prime Minister Narendra Modi has taken stock of the situation and pledged full support to the chief minister. Rescue operations are underway, with many people rescued from the affected areas.

The flash floods have prompted the closure of schools in Mangan, Gangtok, Pakyong, and Namchi districts until October 8. Additionally, neighboring West Bengal, which shares a border with Sikkim, has also faced flash floods, with Chief Minister Mamata Banerjee reporting the rescue of 10,000 people in northern parts of the state.

In hindsight, the devastating flash floods in Sikkim are a stark reminder of the importance of heeding warnings and implementing proactive measures to mitigate the impact of climate change on vulnerable regions. The tragic consequences of inaction should galvanize governments and communities to prioritize environmental sustainability and disaster preparedness. Ignoring red flags can no longer be an option in the face of such dire consequences.

 

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