Ten kilometres south of Mount Everest lies Nepal’s “fastest-growing glacier lake”— Imja Tsho. In March 2016, acting to mitigate potential threats the lake might pose to over 96,000 people downriver, the Nepalese Army began installing syphons to lower the water level by 10 feet (3 m).
The army’s engineering department, commissioned by Nepal’s Department of Hydrology and Meteorology (DHM), is now conducting “the highest altitude disaster risk mitigation work ever performed by any army in the world,” according Lt Col Bharat Lal Shrestha. Locally, the remediation will bolster the confidence of flood-prone communities, and is likely to assuage fears of downstream developers, which have been concerns elsewhere in the region.
The soldiers can only work two to three hours a day, due to the thin air, and strain of working at 16,400 feet (5,000 m). The project aims to safeguard lives, livelihoods, and infrastructure throughout Solukhumbu District — home to Mount Everest and the major religious site of Tengboche Monastery — as well as further downstream.
The United Nations Development Programme (UNDP) and Global Environment Facility (GEF) — the world’s largest fund addressing environmental issues — are financing the US$7.2 million remedial works at Imja Tsho, often cited as an especially dangerous lake. This has been reinforced by local perceptions and its proximity to Everest’s trekking routes.
A report by the BBC in June 2016 claimed that the 2015 Gorkha earthquakes “may further have destabilised” the lake. However, the results of ’Rapid Reconnaissance Surveys’ made public in December 2015 revealed “[Imja] showed no indication of earthquake damage when viewed either by satellite or by a helicopter.”
The UNDP and GEF’s selection of Imja pivots on a single study by International Centre for Integrated Mountain Development (ICIMOD) from 2011, which defies much of the preceding and independent research on the lake. ICIMOD is an intergovernmental agency headquartered in Kathmandu, researching Nepal’s glaciers and mountains hazards and also involved in the current engineering works.
Studies by Japanese, British and American teams concluded that the surrounding topography shelters Imja from mass movements. ICIMOD deprioritized Imja’s status. Their 2011 national report stated, “[despite] the apparently alarming rate of [Imja Tsho’s] expansion…the danger of outburst came to be regarded as far less than originally expected.” Concurring with the international researchers, they also ruled out the possibility of a GLOF-triggering ice avalanche as ”[not] very likely.”
The lead authors of the 2011 study subsequently gave compelling evidence in 2015 for remediation at another glacial lake — Thulagi Tsho. Narendra Raj Khanal and six colleagues from ICIMOD revealed Thulagi posed a “high risk.” Over 164,000 people would be directly impacted by a Glacial Lake Outburst Flood (GLOF), with a further 2 million indirectly exposed — four times the number at Imja. Threats to hydropower facilities were a key concern highlighted by UNDP and GEF. However, there are six hydropower projects below Thulagi, and one below Imja.
Imja is being drained 10 feet (3 m) over 4 years — costing nearly US$7 per gallon. However, research led by the University of Texas has shown that this minor reduction would have a negligible impact on a GLOF. Daene McKinney and Alton Byers also stated that it offered an insignificant “3 percent risk reduction.”
Imja Tsho presently covers 135 ha (1.35 km2), holding nearly 20 billion gallons (75.2 million m3) of meltwater — enough water to meet all New York State’s water needs for nearly two and a half days. It is fed by Imja Glacier, which has wasted 1.4 miles (2.2 km) over less than 40 years. Imja Glacier has “exhibited the largest loss rate in the Khumbu region,” according to research by the University of Texas and The Mountain Institute.
Nepal began inventorying its glaciers and glacial lakes in earnest in 1999 — “after global warming had become a sexy topic,” claimed independent observer Seth Sicroff. ICIMOD publishing the findings in 2001. They detected 2,323 glacial lakes, classifying twenty — less than one percent —as “potentially dangerous.”
GLOFs, which typically occur when a dam barring a glacial lake fails, gained greater attention as a point of investigations in the 1980s, following a catastrophic outburst at Dig Tsho. At the “request” of Khumbu residents, German geoscientists Wolfgang Grabs and Joerg Hanisch travelled to the Everest region in 1993 to study local glacial hazards, and establish an hazard assessment criteria. They speculated that syphoning water, and lowering the level by 16.4 feet (5 m) could “stabilize” lake against overtopping surge waves pouring over the dam.
The syphon was first adopted at Tsho Rolpa — Nepal’s largest glacial lake — in May 1995. By 1998, following 4 years of investigations, Professor John Reynolds — then-chief technical adviser on glacial lakes to the Nepalese government — designated it the “most dangerous glacial lake in Nepal.”
A repeat of the 1985 GLOF has long been feared in Rolwaling Valley — a mere 6 miles (10 km) east of Dig Tsho. The DHM projected Tsho Rolpa could release of over 8 billion gallons (30 million m3) of meltwater — threefold the volume of 1985 GLOF, and equivalent to the volumes of 12,000 olympic swimming pools. Over 10,000 local inhabitants, and US$22 million-worth of infrastructure and property as far as 62 miles (100 km) down-valley, were thought to be threatened.
In 2013, a Japanese research team revealed that the “potential flood volume” at Tsho Rolpa has tripled, and is now closer to 23.6 billion gallons (89.6 million m3).
By July 2000, a 13 foot (4 m) US$3.1 million spillway had been constructed, reducing the water level by 9-13 feet (3-4 m). Reynolds recommended that engineering works be continued until the lake level was 49-65 feet (15-20 m) below its 1998 level. Five DHM experts and Reynolds co-authored a paper emphasising, “While the lowering of the lake level by [9.8 feet] 3 m [was] expected to reduce the risk of GLOF, it is not a permanent solution.” Their explicit intention was to continue lowering in the “near future,” as soon as funds were allocated for disaster mitigation in Nepal.
Funds were never found and, in the early 2000s, Maoist insurgents infiltrated the area. They dismantled Tsho Rolpa’s ‘Community-Based Early Warning System’ (CBEWS) in 2002. It was not until 2012 — a decade after the insurgence had been quelled — that replacements were pledged. The CBEWS was expected to be back online in early 2016.
A misplaced “trust in western technology” resulted in locals complacently believing there was “no further danger,” according to anthropologist Dr Janice Sacherer of the University of Maryland. This sentiment persists, and no further work has been budgeted for Tsho Rolpa in the near future. This is largely attributable to the limited funds available to the DHM, who receive a bulk of their funding from international NGOs, aid agencies and foreign governments.
It has been long been hoped that funds would be diverted to counter the immediate threat posed by Tsho Rolpa. The UNDP’s 2013 technical report stated 141,911 people within 62 miles (100 km) of Tsho Rolpa are exposed to the direct impacts of a GLOF, compared to the 96,767 living 75 miles (120 km) below Imja Tsho. However, the UNDP report justifies its decision to focus on Imja by revealing that the economic toll through lost revenue at Imja would be US$8.98 billion — nearly four times that downstream of Tsho Rolpa.
In 2007, under-development of the Rolwaling Valley was attributed, at least in part, to the omnipresent threat of a massive GLOF.
With a US$7.2 million price-tag, a military cohort that can only work a few hours a day, other sites requiring more immediate attention, and the syphoning method being deemed a “Band-Aid solution,” only time will tell if the money and effort expended on Imja Tsho were warranted.