Thac Ba Hydropower Plant, breathless moments

“Hanoi city, Tuyen Quang, Phu Tho, Vinh Phuc provinces, especially Yen Bai, prepare for the worst possible scenario for Thac Ba lake.”

This is a short passage from Official Dispatch No. 92/CD-TTg that Prime Minister Pham Minh Chinh directly signed and sent to the Secretaries and Chairmen of the People's Committees of relevant provinces and cities on the evening of September 10.

Just a few hours earlier, while Prime Minister Pham Minh Chinh was inspecting the flooding situation in the northern provinces, Deputy Prime Minister Bui Thanh Son signed Official Dispatch No. 91/CD-TTg to send to the Secretaries and Chairmen of the People's Committees of the three provinces of Lao Cai, Ha Giang and Yen Bai to deploy urgent measures to ensure the safety of the Thac Ba hydropower dam.

It all started with a very rapid development from the upper reaches of the Chay River, the largest river supplying water to the Thac Ba Hydropower Plant, an important energy project that the former Soviet Union helped Vietnam build since 1971.

Thac Ba 1971 faces historic storm number 3 2024

Thac Ba Hydropower Plant is located in Yen Bai province, 180km northwest of Hanoi. At the time of construction, it was the largest hydropower plant in the country, with a reservoir that could hold 3.9 billion m3 of water.

The main water source flowing into the lake is the Chay River, and some small rivers such as Hanh Stream, Cat Stream...

Thac Ba Hydroelectric Reservoir

The Chay River receives water from the forests and mountains of Ha Giang, Lao Cai, and Yen Bai provinces. The lake water flows through the generators and the main dam's spillway into the Chay River, continues along the stream, and then merges with the Lo River in Doan Hung District, Phu Tho.

From here, the Lo River flows down, together with the Da River from the Northwest region, converging with the Red River at the Bach Hac junction, Phu Tho, and flows to Hanoi and the delta provinces before emptying into the sea.

At that time, Soviet experts used the historical flood that could be recorded on the Chay River, with a flow rate of more than 4,000m3/s in 1961, to design the Thac Ba hydropower plant. Accordingly, 3 surface discharge gates along with the generators were designed with a maximum discharge capacity of more than 3,000m3/s.

However, storm No. 3 has suggested new historical anomalies for the entire vast North, including the small Thac Ba of Yen Bai.

The storm, internationally named YAGI, became the strongest super typhoon in the past 30 years to enter the East Sea, and even the strongest in the past 70 years when it crossed Hainan Island and then went straight to the coast of Hai Phong, Quang Ninh, cut through Hai Duong, Hung Yen and then hit Hanoi, before gradually dissipating in the remote Northwest region.

Storm No. 3 dissipated on September 9, while the northeastern provinces faced record-breaking heavy rains. The mountains and forests of Ha Giang, Lao Cai, Tuyen Quang, and Yen Bai received a huge amount of rain, causing the water level in Thac Ba Lake to continuously increase.

By 9:00 a.m. on September 10, the water flow reached a historic level of 5,600 m3/s, higher than the historical flood used as a design basis, and nearly double the flood discharge capacity of the main dam.

The water level in the lake rose hourly with the forecast that a disaster would soon occur if no timely response was taken. Working groups from the Ministry of Agriculture and Rural Development and the Ministry of Industry and Trade immediately arrived at the scene, along with the Yen Bai authorities, relevant localities, and Thac Ba Hydropower Joint Stock Company to assess the situation.

Prime Minister's emergency meeting and unprecedented evacuation

On the afternoon of September 10, Prime Minister Pham Minh Chinh was inspecting the flood situation and response work in Bac Giang province, stopping to have an online meeting with the Government Headquarters, and Yen Bai, Tuyen Quang, Phu Tho, Vinh Phuc, and Hanoi.

One of the contents of the report that the Prime Minister heard was the serious situation of Thac Ba Hydropower Plant. From there, important initial decisions were made.

Prime Minister Pham Minh Chinh inspected the flood in Bac Giang province on the morning of September 10, then held an online meeting with Yen Bai and other northern provinces. Photo: Nhat Bac

At the Government Headquarters, Deputy Prime Minister Bui Thanh Son signed an official dispatch to deploy emergency measures to ensure the safety of the Thac Ba hydropower dam.

Technical solutions were also deployed, including choosing Thac Ba's auxiliary dam No. 4 as the point for dam demolition plans, proactively reducing the water level in the lake when ordered.

In addition, since the morning of the same day, there has been a pre-emptive order for the emergency evacuation of people and property in areas that are likely to be flooded due to proactive dam demolition. The grassroots political system of the relevant districts, villages, and communes of Yen Bai, and even the neighboring Phu Tho region, immediately took action to inform people to prepare.

Calculations show that 3,186 households with more than 11,279 people in the area of ​​24 villages and residential groups in Vinh Kien, Yen Binh, Han Da, Dai Minh communes, Thac Ba town of Yen Binh district, Yen Bai province need to be moved to higher and safer areas.

After the Prime Minister's afternoon meeting concluded, from 1:00 p.m., forces at all levels began to carry out the evacuation.

The spirit is still “four on-site”: Mobilize people to stay at relatives and acquaintances outside the affected area. Then gather at government offices, schools, and clinics. If there are not enough, then camp.

The people complied very well. Those who were left had their possessions. Each person brought their personal papers to the evacuation site, leaving behind their property and homes, in the peace of mind of their fellow countrymen's feelings and responsibilities and under the watchful eyes of the police and military forces.

By 5pm, everything was done. Yen Bai was ready for the worst…

Breathtaking moments

Thac Ba is an artificial lake located between the undulating mountains and hills. To build this project, the space between the old streams, rivers and streams was blocked by earthen dams, becoming 62m high auxiliary dams. The main dam is located across the Chay River, in Thac Ba town, Yen Binh district.

By design, this is a multi-purpose lake, for flood control, irrigation, and electricity production.

During the rainy and stormy season, especially when there was news of storm number 3, Thac Ba lake was operated at maximum capacity to reduce the water level to a deep level, lower than the normal rising water level, ready to welcome the flood.

However, the impact of storm No. 3 and extreme weather has appeared. Even opening all 3 floodgates is still not enough to keep up with the amount of water pouring in from the source. From a very low water level to welcome the flood, this hydroelectric reservoir quickly filled up, equaling and then exceeding the normal water level, and quickly rising to 59.6m. This is the point of transition to emergency status according to the operating regulations.

The 4th auxiliary dam, about 50m long, in the Han Da commune area was selected. Along with that, the evacuation of people was carried out one step ahead and completed. If the upstream flood situation does not improve, the water level in the lake rises to 61m, then on the morning of September 11, the most undesirable thing will have to be done...

All evening and night of September 10, the whole of Yen Bai held its breath.

On social networks, people interested in and knowledgeable about this situation are anxious.

According to monitoring data from Thac Ba Hydropower Plant, at 5:00 p.m. on September 10, the upstream water level had reached 59.62 m. At the same time, the water flow, although lower than the record at 9:00 a.m., was still 4,450 m3/s. All generators were operating and all three sluice gates were open, but only more than 3,003 m3/s was discharged.

At 11pm, the water level decreased a bit, to 4,115m3/s, but the discharge capacity was not at its maximum, so the lake water level increased to 59.78...

But at the same time, upstream meteorological monitoring information in the system by the General Department of Hydrometeorology under the Ministry of Natural Resources and Environment showed that rain began to decrease sharply.

By around 11am on September 11, the water flow into Thac Ba Lake had decreased to 3,180 m3/s, equivalent to the discharge capacity of the main dam. Throughout the night of September 10 until noon on September 11, the lake water level continued to increase, but slowed down, then stopped. By 1pm, the water flow into the lake was 2,992 m3/s, lower than the discharge at the same time, 3,005 m3/s. The water level of Thac Ba Lake could have decreased, albeit slowly. So the important 61m mark could be protected...

Comrade Tran Huy Tuan - Deputy Secretary of the Provincial Party Committee, Chairman of the Provincial People's Committee, and leaders of Yen Binh district inspected the flood. Here, Mr. Tuan emphasized the need to closely review all households in the flooded area due to the discharge of floodwater from Thac Ba Hydropower Plant to promptly evacuate to a safe place. Photo: Yen Bai Newspaper

Pre-order and active orders

In recent days, when the situation was tense, Yen Bai city and low-lying areas of the province, sandwiched between the Red River and the Chay River, suffered from deep flooding due to the historic flood.

Faced with this situation, Minister of Natural Resources and Environment Do Duc Duy, who had just left his duties as Secretary of the Yen Bai Provincial Party Committee to take up the position of Minister at the end of August, was assigned by the Prime Minister to return to directly direct flood and landslide prevention after storm No. 3.

Returning to the place where he has been attached for 7 years, since being unexpectedly mobilized in 2017, Mr. Duy and Chairman of Yen Bai People's Committee Tran Huy Tuan have divided the work among themselves, some staying to take care of people in flooded areas, others going to Thac Ba, preparing for the worst case scenario.

But heaven and earth were in favor so that the draft order on Prime Minister Pham Minh Chinh's desk did not become a decree.

And at noon on September 11, Mr. Tuan was able to withdraw from Thac Ba to return to the provincial headquarters to continue dealing with the consequences of flooding and inundation.

Mr. Duy can now return to the headquarters of the Ministry of Natural Resources and Environment with peace of mind to continue organizing the implementation of the Land Law with a series of decrees that are an important legal framework expected to create new momentum for the economy, during the period when the country has entered and is entering a generational leadership transition as the 14th Congress is approaching.

Hanoi, Yen Bai as well as the midland and mountainous provinces in the North have now become drier. According to the plan of Yen Bai leaders, if things continue to improve like this on the night of September 11, more than 3,186 households with more than 11,279 people can soon return to their homes in 24 villages and residential groups of Yen Binh district.

After a few days of experiencing the sudden evacuation, they will return to normal life, and then everything will gradually become a memory. Memories of breathless moments and to feel more clearly the smallness of humans before Mother Nature, September 2024.

Vietnamnet.vn

Source: https://vietnamnet.vn/thuy-dien-thac-ba-nhung-phut-giay-nin-tho-2321201.html