An expedition from department of hydro-met services will be fielded soon to study the outburst and ascertain the lake’s name
Flood: The Lemthang tsho (lake) outburst on June 28 evening in Laya washed away six wooden bridges (bazams) including the only bridge that connects Laya to the rest of Gasa dzongkhag.
Gasa dzongdag Dorji Dhradhul said a team of three groups were sent to various locations to find out if there were any signs of formation of artificial lakes. “Locals confirmed yesterday morning that the lake had emptied by last night,” he said.
The dzongdag’s report to the department of disaster management stated that the plain area in front of the lake is covered in sand and debris that the outburst left behind.
As it gushed downstream, it washed away Bazi zam, which is two hours from Laya towards the lake, Pazi zam, which is 15 minutes from Laya village, Lhupja zam, which is 30 minutes from Laya village and Baru zam, which is an hour away from Laya and near Tashi Makhang.
The outpour also washed away the Tongchudrak zam, which is three hours away from Laya towards Gasa and the Lemthang zam near the lake.
Dzongdag Dorji Dhradhulsaid although they were small wooden bridges, they were important in connecting the dzongkhag and with the bridge at Tongchukdark gone, no one could either travel to or from Laya.
A team of park officials and local leaders of Laya were sent to check from Laya to Tashimakhang, while another team of army personnel was deputed from Tashimakhang to Tongchudrak. A third group including army, police and dzongkhag officials inspected from Gasa towards Laya.
“We were trying to physically verify existence of artificial lakes and other damages along the river,” the dzongdag said.
Park officials said around 300 cordycep collectors are also stranded on the other side of the lake. “No casualty has been reported so far but given the intensity of the outburst, we are expecting some livestock casualty,” Jigme Dorji National Park manager, Lhendup Tharchen said.
Since June 28 night, he said, park officials on duty in Laya have been monitoring the situation. The team left early morning for the burst site yesterday but with the Bazi zam washed away, they had to return to Laya.
“The team will again try to visit the site today to assess the damage from the outburst and see the situation of the cordycep collectors,” he said.
Meanwhile, the Department of Hydro-met Services (DHMS) will soon depute an expedition to Laya to confirm which lake had breached and study how it had occurred.
Of the 25 lakes that are potentially dangerous, five are in the Mo Chu basin. “Only a physical verification would confirm if the lake that had breached was among the five,” the chief of hydrology division Karma Dupchu said. “Until and unless we go there, we will not know if the rain or earthquake or both triggered the flashflood because we don’t have any details about that lake.”
Records from the GLOF early warning system in Wangdue, which is manned round the clock, showed that although the outburst was reported around 6.30pm, the first flood peak arrived at Taktse Makhang, Laya station at 7.30pm.
“The first time, the lake may have partially breached and the highest water level recorded at 7.30 pm was 6.660m,” Karma Dupchu said. “Then the water level receded and the second flood peak arrived an hour later at 8.30pm.”
Members of the GLOF Management Oversight Group (GMOG) who were informed immediately after receiving the information on the breach monitored the early warning system from Thimphu until 1.30am yesterday morning. Some 30 officials in Gasa were also monitoring and updating the status of flood from Gasa Tsachu until the disaster management department declared the situation safe.
“We were monitoring the flood downstream, and in one hour 45 minutes, it reached the next station at Trashithang, which is about 45 km downstream,” Karma Dupchu said.
The flood took almost two hours, 45 minutes to reach the third station at Yebesa, which is about 75 km from Taktsemakhang. The stations record the water level every 15 minutes.
Although the water level observed at Taktsemakhang was below the alert level of 7.5m, Karma Dupchu said the sirens were manually activated at 8.48pm to warn people downstream because of the information that the lake had completely breached and that there were two impeding floods.
He said the other reason to activate the sirens was because the water level downstream were already high from the incessant rainfall. “There were high chances that further floods from the outburst would increase the water level downstream,” he said.
On June 27 night and 28th morning, Gasa received heavy rainfall. It recorded 3.75mm of rain on the 27th. With monsoon still on, the early warning systems would continue monitoring the water levels.
“But we are not sure if the lake has emptied,” he said. “The good thing was we could test our early warning system and confirm that all sirens worked.”
Meanwhile, the two drinking water pipes connecting Bajo town that was washed away in Wangdue was fixed yesterday evening.
The environment officer with Punatsangchu project, Sangay Dorji said the highest water level was recorded as 1,198 cubic meters per second. The environment team was monitoring the water level until 4:30am yesterday.
In Punakha, no major problems were reported after the floods and after more than three weeks of rain, the sky cleared in Gasa yesterday. By afternoon, the dzongkhag’s power supply was also restored.
By Sonam Pelden & Dawa Gyelmo