Thac Ba Hydroelectric Power Plant: Moments of Breathtaking Moments

" Hanoi city, Tuyen Quang, Phu Tho, Vinh Phuc provinces, and especially Yen Bai, are preparing for the worst-case scenario regarding Thac Ba Lake."

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

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

It all stems from the very rapid developments upstream of the Chay River, the largest river supplying water to the Thac Ba hydroelectric power plant, a crucial energy project built with assistance from the former Soviet Union to Vietnam since 1971.

Thac Ba waterfall in 1971 faces the historic Typhoon No. 3 in 2024.

The Thac Ba hydroelectric power plant is located in Yen Bai province, 180km northwest of Hanoi. At the time of its construction, it was the largest hydroelectric power plant in the country, with a reservoir capable of holding 3.9 billion cubic meters of water.

The main water source for the lake is the Chay River, and some smaller streams such as Hanh stream, Cat stream, etc.

Thac Ba hydroelectric reservoir

The Chay River receives water from the mountainous forests of Ha Giang, Lao Cai, and Yen Bai provinces. The reservoir's water then flows into the Chay River through the main dam's turbines and spillways, continuing downstream before merging with the Lo River in Doan Hung district, Phu Tho province.

From here, the Lo River flows downstream, joining the Da River from the Northwest region to merge into the Red River at the Bach Hac confluence in Phu Tho, and continues flowing towards Hanoi and the delta provinces before emptying into the sea.

At that time, Soviet experts used the historical flood levels recorded on the Chay River in 1961, with a flow rate of over 4,000 m3/s, to design the Thac Ba hydroelectric power plant. Accordingly, the three surface spillway gates along with the turbines were designed with a maximum discharge capacity of over 3,000 m3/s.

However, Typhoon No. 3 has suggested new historically unusual factors for the entire northern region, including the small Thac Ba area of ​​Yen Bai province.

The storm, internationally named YAGI, became the strongest super typhoon to enter the South China Sea in the past 30 years, and possibly even the strongest in the past 70 years, as it crossed Hainan Island and then directly hit the coast of Hai Phong and Quang Ninh, cutting through Hai Duong and Hung Yen before striking Hanoi and gradually dissipating in the remote Northwest region.

As Typhoon No. 3 dissipated on September 9th, the northeastern provinces of Vietnam simultaneously faced record-breaking, prolonged heavy rainfall. The forests and mountains of Ha Giang, Lao Cai, Tuyen Quang, and Yen Bai received an enormous amount of rain, causing the water level in Thac Ba Lake to rise continuously.

By 9:00 AM on September 10th, the water inflow reached a historic level of 5,600 m3/s, exceeding even the historical flood level used as the basis for the design, and nearly double the main dam's flood discharge capacity.

The water level in the reservoir was rising hourly, with predictions that a disaster could soon occur if timely countermeasures were not 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 provincial government, relevant localities, and Thac Ba Hydropower Joint Stock Company, to assess the situation.

An emergency meeting of the Prime Minister and an unprecedented evacuation.

At noon on September 10th, Prime Minister Pham Minh Chinh, while inspecting the flood situation and response efforts in Bac Giang province, stopped to hold an online meeting with the Government Headquarters and other locations including Yen Bai, Tuyen Quang, Phu Tho, Vinh Phuc, and Hanoi.

One of the topics the Prime Minister heard reports on was the serious situation at the Thac Ba hydropower plant. Based on this, important initial decisions were made.

Prime Minister Pham Minh Chinh inspected flood relief efforts in Bac Giang province on the morning of September 10th, then held a virtual meeting with participants from Yen Bai and other northern provinces. Photo: Nhat Bac

At the Government Headquarters, Deputy Prime Minister Bui Thanh Son signed a dispatch implementing urgent measures to ensure the safety of the Thac Ba hydroelectric dam.

Technical solutions were also implemented, including selecting auxiliary dam No. 4 of Thac Ba as the focal point for planning the dam's demolition, proactively reducing the water level in the reservoir when ordered.

Furthermore, since that morning, there has been a warning about the possibility of emergency evacuation of people and property from areas prone to flooding due to the planned dam breach. The local political systems in the relevant districts, villages, and communes of Yen Bai, and even in neighboring Phu Tho, immediately swung into action, informing residents to prepare.

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

Following the Prime Minister's concluding remarks at the midday meeting, starting at 1 PM, forces at all levels began implementing the evacuation.

The guiding principle remains "four on-site": Encourage people to stay with relatives or acquaintances outside the affected area. Only then should they gather at government offices, schools, or health centers. Only if there is a shortage of temporary shelters should they be set up.

The people complied very well. Those who remained had their belongings. Each person brought their personal documents to the evacuation site, leaving their property and houses behind, under the reassuring care and responsibility of fellow citizens and the supervision of the police and military forces.

By 5 PM, everything was complete. Yen Bai was ready for the worst-case scenario…

Breathtaking moments

Thac Ba is an artificial lake nestled amidst rolling hills and mountains. To construct this structure, the areas between the streams and rivers were previously dammed with earthen dams, creating auxiliary dams 62 meters high. The main dam spans the Chay River in Thac Ba town, Yen Binh district.

By design, this is a multi-purpose reservoir, serving flood control, irrigation, and power generation.

During the rainy season, especially when news of typhoon number 3 began to arrive, Thac Ba Reservoir was operated at maximum capacity to lower the water level significantly, even below the normal water level, in preparation for floods.

However, due to the impact of Typhoon No. 3, extreme weather conditions occurred. Even opening all three floodgates was insufficient to handle the volume of water flowing in from upstream. From a very low water level intended for floodwaters, the reservoir quickly filled up, reaching and then exceeding the normal water level, and rapidly rising to 59.6 meters. This marks the point at which the reservoir is transitioned to an emergency state according to operating regulations.

The fourth auxiliary dam, approximately 50 meters long, located in Han Da commune, was chosen. Simultaneously, the relocation of residents was carried out and completed as a preliminary step. If the upstream flood situation does not improve and the water level in the reservoir rises to 61 meters, then on the morning of September 11th, the most undesirable course of action will have to be taken…

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

On social media, those who are concerned and knowledgeable about the situation are feeling anxious.

According to monitoring data from the Thac Ba hydropower plant, at 5 PM on September 10th, the upstream water level reached 59.62 meters. At the same time, although the inflow decreased compared to the record high at 9 AM, it was still 4,450 m³/s. Even with all turbines operating and all three spillway gates open, only just over 3,003 m³/s of water could be discharged.

By 11 PM, the water inflow had decreased slightly to 4,115 m3/s, but the discharge capacity was not at its maximum, so the reservoir water level rose to 59.78...

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

By approximately 11:00 AM on September 11th, the water inflow into Thac Ba Lake had decreased to 3,180 m3/s, equivalent to the main dam's discharge capacity. Throughout the night of September 10th until noon on September 11th, the lake water continued to rise, but at a slower pace, and then stopped. By 1:00 PM, the inflow had reached 2,992 m3/s, lower than the discharge rate at the same time, which was 3,005 m3/s. The water level in Thac Ba Lake was able to decrease, albeit slowly. Thus, the crucial 61m mark can be protected…

Comrade Tran Huy Tuan – Deputy Secretary of the Provincial Party Committee, Chairman of the Provincial People's Committee, along with leaders of Yen Binh district, inspected the flood-affected area. Here, Mr. Tuan emphasized the need for a thorough review of all households in the flooded area caused by the Thac Ba hydropower plant's water release, in order to promptly relocate them to safe areas. (Photo: Yen Bai Newspaper)

Preliminary orders and execution orders

In recent days, amidst the tense situation, Yen Bai city and the low-lying areas of the province, nestled between the Red River and the Chay River, have suffered severe flooding due to a historic flood.

In light of this situation, Minister of Natural Resources and Environment Do Duc Duy, who had just stepped down as Secretary of the Yen Bai Provincial Party Committee to assume the position of Minister at the end of August, was assigned by the Prime Minister to return to directly supervise flood and landslide prevention and control efforts following Typhoon No. 3.

Returning to the place where he had spent seven years since his unexpected assignment in 2017, Mr. Duy and the Chairman of the Yen Bai Provincial People's Committee, Tran Huy Tuan, divided up the tasks: one stayed behind to care for the people in the flooded areas, while the other went to Thac Ba to prepare for the worst-case scenario.

But fate intervened, ensuring that the order on Prime Minister Pham Minh Chinh's desk did not become an actual order.

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

Meanwhile, Mr. Duy can now confidently return to the Ministry of Natural Resources and Environment headquarters to continue organizing the implementation of the Land Law, along with a series of decrees that form an important legal framework expected to create new momentum for the economy, at a time when the country is undergoing a generational leadership transition as the 14th National Congress is fast approaching.

Hanoi, Yen Bai, and other provinces in the northern midland and mountainous regions are now drier. According to Yen Bai's leaders, if conditions continue to improve throughout the night of September 11th, more than 3,186 households with over 11,279 people may soon be able to return to their homes in the 24 villages and residential areas of Yen Binh district.

After a few days experiencing the unexpected evacuation, they will return to normal life, and then it will all gradually become a memory. A memory of those breathless moments, and of feeling more acutely the insignificance of humanity before Mother Nature, September 2024.

Vietnamnet.vn

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