With Khurdopin glacier in its surge phase since last year, disaster management teams in the Gilgit-Baltistan region are monitoring a lake formed by the glacier’s blockage of Shimshal River for possible outburst floods in summer months.
A study of Khurdopin glacier using high-resolution optical satellite imagery during the surge in 2017 contends that the glacial lake may grow further in area this year and in 2019. A sudden breach may cause a Glacial Lake Outburst Flood (Glof). The effect of such a flood on downstream settlements and infrastructure yet remains uncertain, according to officials at GB Disaster Management Authority (GBDMA) and Aga Khan Agency for Habitat (AKAH).
The satellite imagery studied by the team led by Jakob F. Steiner of the Utrecht University’s Physical Geography Department shows that for a few weeks in 2017, Khurdopin glacier’s velocity peaked to above 5,000 metres per year (ma-1), which is among the fastest rates reported globally. On a day during these weeks, the research team found the peak velocity on a part of the glacier to be 20 m/day, Prof Steiner shared with MIT Technology Review Pakistan in an email exchange.
Surges in Khurdopin glacier have been known to recur over a 20-year cycle at least since the 19th century.
The study published in Cryosphere, a peer-reviewed open access journal, compares the glacial lake formed due to river’s blockage last year with the one formed during the previous reported surge in 1999, and contends that in 2018 and 2019, the lake may extend to beyond a square kilometre in area during the melt season that begins in May.
In the melt season last year, the drainage of the lake had started in late July and went on till the first week of August. It resulted in a moderate flood, affecting road network on multiple locations, destroying at least one main bridge, eroding agricultural land, and leaving the valley inaccessible for a week.
Over the years, the communities living downstream developed an early warning system using bonfires set up along the slopes of Shimshal Valley. The onset of telecommunication technology in the region over the last decade has replaced that traditional method with the use of cellular phones.
AKAH teams have been monitoring changes in glaciers in Shimshal Valley with assistance of communities settled downstream for five years now. In a written response to MIT Technology Review Pakistan’s queries, the AKAH says that since the start of the surge in May 2017, it has been in contact with the Pakistan Meteorological Department (PMD), the GBDMA, and community representatives.
The AKAH teams have visited the site four times, conducting aerial surveillance twice using helicopters provided by the Aga Khan Development Network (AKDN).
Based on these visits, the AKAH has calculated that the length of the glacial lake has more than doubled since November last year, when it was measured at around 700 metres. The recent measurement taken in early January was about 1.5 kilometres, suggesting that the area of the lake may already have crossed the one-square-kilometre figure estimated by the Utretch researchers.
“The length of the section blocking the river is just over two kilometres but it can increase as the surge continues,” says the AKAH team.
While the lake is frozen at the moment, it will start melting once temperatures in the region start rising in April. “The melting of the glacier can accumulate more water into the lake and it may lead to a critical situation. The resulting glacial lake outburst flood will impact settlements and community infrastructure in downstream villages surrounding Attabad Lake” it says.
The AKAH says it has shared its assessment report alongside all key findings with the District Commissioner (DC) of Gilgit.
Other measures taken by the agency include installation of weather monitoring posts (WMP) in the region to keep a check on changes in temperature and weather patterns and their effect on the glacier. “Using information received form these WMP, situation alerts and warnings are developed and shared with the community for timely action,” the AKAH says.
It has also trained a team of community volunteers known in the region as ‘Glacier Monitoring Team’ that visits Khurdopin and other glaciers once every month to monitor changes.
GBDMA assistant director general Gufran Ubaidullah, who is posted in Shimshal region, maintains that the possibility of an outburst flood and the extent of threat from it to downstream communities will become clearer by the end of March. “We can’t say anything for sure before that because the glacier is frozen at the moment and there is no water flowing into the lake due to below zero temperatures in the region. Once temperatures start falling, we will have a clearer assessment of the flood hazard,” he says.