Nepal’s Glacial Lakes in Danger of Bursting

Tso Rolpa glacial lake at 4,580m has grown seven times in size in the past 60 years due to global heating. Credit: RASTRARAJ BHANDARI

Tso Rolpa glacial lake at 4,580m has grown seven times in size
in the past 60 years due to global heating. Credit: RASTRARAJ
BHANDARI

By Mukesh Pokhrel
KATHMANDU, Sep 14 2020 (IPS)

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
Tso Rolpa glacial lake in the Rolwaling Valley
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.

�

A sluice gate built 20 years ago reduced the level of the water by 3m, but it needs to go down by 20m to reduce the danger of a Glacial Lake Outburst Flood (GLOF). Credit: RASTRARAJ BHANDARI

A sluice gate built 20 years ago reduced the level of the water
by 3m, but it needs to go down by 20m to reduce the danger of a
Glacial Lake Outburst Flood (GLOF). Credit: RASTRARAJ BHANDARI

 

The other project was a
drainage channel and gate built on Imja Lake
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 cost
of $7.2 million
.

The project located at 5,000m altitude was
criticised at the time
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

Thulagi in Lamjung
 on the
Hongu basin
were said to be in much greater danger of bursting,
and
needed more urgent mitigation
.

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.

The Glacial Lake Inventory report launched at a
webinar
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
International Centre for Integrated Mountain Development
(ICIMOD)
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.

 

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.

The lakes are expanding because the ice fields feeding them are

melting faster due to global heating,
as well as increased
deposition of soot particles on the snow.
An ICIMOD assessment
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
glacial lake outburst flood (GLOF) events
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.

This story was originally
published
 by The Nepali Times

The post
Nepal’s Glacial Lakes in Danger of Bursting
appeared first on
Inter Press Service.

Source: FS – All – Ecology – News
Nepal’s Glacial Lakes in Danger of Bursting