Operating a generator when the lake water level drops below the dead water level, both the staff and the management of Thac Ba Hydropower Plant are always tense, worried about an incident.
At midnight on June 9, the alarm clock rang and Mr. Phung Dinh Hai, the head of the waterworks team at Thac Ba Hydropower Plant (Yen Binh District, Yen Bai) jumped out of bed. Wearing his power company uniform, he took a specialized measuring tape and rode his motorbike to the hydropower dam to measure the water level. This is a task that occurs three times a day since the water level is lower than the location of the automatic measuring device.
During the more than one kilometer journey from his house to the dam, Mr. Hai kept asking himself: Is there a lot of water today? Is the lake water level enough to generate electricity again? Arriving at the factory, he walked quickly to the dam wall, dropped the measuring tape to the water surface, shined a flashlight at the display position and shook his head when the water level almost did not change compared to 8 hours ago.
"In more than 10 years of working here, I have never seen the water level of Thac Ba hydroelectric reservoir drop so low and take so long to rise again," Mr. Hai said while recording data to report to the on-duty room.
Thac Ba Hydropower Control Room. Photo: Ngoc Thanh
On June 1, the lake water level dropped to 45.57 m, below the dead water level (the minimum water level to operate the generators is 46 m). The distance from the water surface to the normal water level is nearly 13 m. For the first time in 52 years of operation, the 120 MW Thac Ba Hydropower Plant had to stop two generators. The remaining generator with the best quality ran at a moderate level, creating just enough flow downstream to ensure the water environment.
Right below the dam surface is the operator's house with 5 staff on duty. Without taking his eyes off the parameter display screen, Mr. Nguyen Manh Cuong, Deputy General Director of Thac Ba Hydropower Joint Stock Company, worriedly said that operating the generator in its current state could cause an incident at any time. Every index exceeding the limit requires urgent response measures.
Leaving the control room, Mr. Cuong went down to the turbine observation room. The closer he got, the louder the noise became. Listening to the vibrations, with many years of experience, he could recognize the level of impact and request to stop the generator when necessary. In 2016, when the water level was low, the fan blades of all three generators were cracked, and the repair took a lot of time and money.
With two generators out of operation, the on-duty team still has to check daily to ensure the machines are ready to operate again when the water returns. Normally, in June every year, Thac Ba Hydropower Plant produces about 20 million kWh, but in the first 10 days of June this year, it only produced 2 million kWh. If the water does not return to the lake, the plant's production plan cannot be completed.
Lai Chau Hydropower Plant stopped operating on June 9. Photo: Ngoc Thanh
The situation at Lai Chau Hydropower Plant, with a capacity of 1,200 MW, is even more serious. Since June 2, the reservoir has fallen below the dead water level, forcing the shutdown of six generators. Lai Chau Hydropower Plant is located at the headwaters of the Da River, with two other hydropower plants downstream: Son La (capacity of 2,400 MW) and Hoa Binh (1,920 MW). The river water cannot flow down, forcing Son La Hydropower Plant to stop operating. Hoa Binh Hydropower Plant will only operate for about another week.
Mr. Luu Khanh Toan, Deputy Director of Son La Hydropower Plant (in charge of Lai Chau Hydropower Plant) said that both Lai Chau and Son La reservoirs were below dead water level for the first time. Before stopping operations, the generators only reached 50-60% capacity.
More than 500 km from Thac Ba, Lai Chau, Ban Ve Hydropower Plant with a capacity of 320 MW - the largest of 40 hydropower plants in Nghe An - is also facing water shortages. On June 7, the water level in Ban Ve was 157 m, 20 m lower than the same period last year and only 2 m higher than the dead water level. The current water flow into the lake is only 1/3 compared to the same period last year.
Mr. Ta Huu Hung, Director of Ban Ve Hydropower Company, said that a few years ago, the water level in the lake was approaching the dead water level - 155 m. However, that situation occurred at the end of July when the rainy season began, and the area then had heavy rains so the lake was replenished with water. Now, at the beginning of June, the water level has dropped to 157 m for the first time. In the next few days, if there is no heavy rain, the lake will return to the dead water level.
"Everyone who builds hydropower plants hopes for a lot of water to ensure electricity supply and irrigation for downstream areas. In the near future, if the reservoir reaches a dead water level, there will be a risk of not being able to supply enough electricity to the system and a lack of water for downstream areas. It's the beginning of the summer-autumn crop, and a lack of irrigation water will affect the crop season and reduce crop yields. We are very worried," said Mr. Hung.
Water level of Ban Ve Hydropower Plant on June 7. Photo: Duc Hung
Located in the upper reaches of the Thu Bon River, Bac Tra My District, Quang Nam Province, the Song Tranh 2 Hydropower Plant with a capacity of 190 MW has not yet run dry. However, due to the prolonged heat, the water volume in the lake is only 260 million m3, equal to 49% of the design capacity.
As the largest hydroelectric reservoir in Quang Nam, Song Tranh 2 discharges about 70-80 m3/s downstream every day, three times higher than the water flow into the lake. "It's not raining, the water flow into the lake is only low, but the unit still maintains the regulation of water downstream to prioritize drought prevention," Mr. Tran Nam Trung, Director of Song Tranh Hydropower Company, explained.
It is forecasted that from June to August, Song Tranh 2 Lake will face difficulties in supplying water for daily life and agricultural production to the downstream area and is at risk of not being able to accumulate more water to the normal rising level by the end of this year to serve the dry season in 2024.
"The company is coordinating with Quang Nam province to optimally regulate water resources, working with the National Power System Control Center to operate generators during peak hours to meet increased load demand, contributing to ensuring national energy security," Mr. Trung added.
Song Tranh 2 Hydropower Plant in early June. Photo: Dac Thanh
According to the Department of Industrial Safety and Environment (Ministry of Industry and Trade), 9 hydropower reservoirs are below the dead water level. Generators at 11 plants such as Son La, Lai Chau, Huoi Quang, Thac Ba, Tuyen Quang, Ban Ve, Hua Na, Trung Son, Tri An, Dai Ninh, Pleikrong must stop generating. The amount of water flowing into the reservoirs is mainly for regulation, ensuring minimum flow. Therefore, the North is currently short of about 5,000 MW, forcing it to have rotating power cuts, without notice, since the end of May until now.
Meanwhile, according to the National Center for Hydro-Meteorological Forecasting, the North will have many days of rain in the coming days, but the water level in rivers and hydroelectric reservoirs will continue to be lower than the average of many years. In the forecast for the next two months, due to the influence of El Nino, heat waves will continue to appear more days than the average of many years in the North and Central regions. Rainfall in the North tends to be 5-20% lower.
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