How long will it take to release water from the Three Gorges Dam to prevent floods? What about the fish?
The Three Gorges is a magnificent water conservancy project in China. As the world's number one hydropower station, its water storage capacity is particularly amazing. The maximum water storage capacity can reach 39.3 billion cubic meters, which is enough for an average urban family to use for 350 million years. Supply all water for 10 years in Beijing. With such an exaggerated water storage capacity, if the gate of the Three Gorges is opened to release all the water at one time, how long will it take to discharge all of it? Let's start with the design and construction of the Three Gorges Dam.
The dam has a total of 54 drainage gates, including 22 gates with a diameter of 8 meters, 23 gates with a diameter of 9 meters, and there are 9 auxiliary drainage gates. The construction of these gates is also very special. All of them drain water in the air. The scene is very spectacular. When the weather is clear, you can also see the rainbow formed by the sun reflecting on the water mist in mid-air. The engineers of the dam designed this way. The way of drainage also has scientific considerations.
If the water is drained directly, it is not a good thing for the dam. The turbulent water column will directly hit the base of the dam, and the force is amazing. This is the case for a long time. The Three Gorges Dam is poured with cement, and no matter how hard the cement is, it will be topped. Do not stop, there is a risk of collapse. As the saying goes, the power of water droplets to pierce through stones cannot be underestimated. Engineers designed and installed a concrete triangular guide groove at the dam outlet. When high-pressure water flows through the guide groove, the kinetic energy of the flowing water will be consumed, and the direction of the water flow will be changed to the sky, and the water flow will fall. When it comes, there is only its own gravity, but no impact force, which greatly reduces the loss of the dam base. For a thousand-year-old project like the Three Gorges Dam, this is the only way to ensure that the entire project will not be eroded by water flow all the year round and ensure the quality and safety of the project.
After scientific calculation, if the 54 gates of the Three Gorges Dam are fully opened, the water flow per second can reach 79,000 cubic meters. According to the maximum water storage capacity of the Three Gorges Dam of 39.3 billion cubic meters, it will take a total of 138 hours and a total of about 5.7 days. . But at the same time, the water storage of the Three Gorges Dam will not be interrupted. The upper reaches of the Yangtze River can inject water into the Three Gorges Dam at a speed of 15,000 cubic meters per second. Taking this factor into account, it takes 170 hours to empty the full Three Gorges Dam. , a total of about 7.1 days. Then if the Three Gorges Dam is completely emptied and all gates are closed, how long will it take to refill it again? After a simple calculation, it takes about 727 hours, a total of 30 days.
Of course, the above calculations are all mathematical simulations. In reality, it is impossible to empty the Three Gorges Dam in one go, otherwise it will inevitably lead to severe floods in the Yangtze River Basin. The water storage and release of the Three Gorges Dam is scientifically planned, and it is responsible for the adjustment of the water volume in the middle and lower reaches. It stores water during the flood peak period of the rainy season and releases water again during the drought and flood period. Therefore, the Three Gorges Dam also has a very important function. Flood control benefits .
The Yangtze River is a rain-flood river. The rainfall in the basin is very abundant, and the annual average rainfall can reach 1100 mm. However, due to the wide basin of the Yangtze River, the rainfall in the southeast reaches is significantly higher than that in the northwest. There are also obvious rainy seasons and dry seasons in terms of time. The precipitation is mainly concentrated in the period from May to October each year. The precipitation in these six months can reach about 80% of the annual precipitation. Therefore, before the construction of the Three Gorges, as long as there is a heavy rainstorm , it is easy to form a major flood. In 1998, due to the long-term torrential rain in the Yangtze River basin, the water level rose rapidly, causing a catastrophic flood disaster that has not been encountered in a century, and the direct economic loss was as high as 166 billion yuan. The completion of the Three Gorges Dam can store water in the rainy season and release water in the dry season, scientifically adjust the water level of the entire Yangtze River Basin, and effectively prevent floods from flooding. would cause such a huge loss.
In addition, the power generation efficiency of the Three Gorges Dam is also very amazing. There are thirty-four hydro-generator units installed in the Three Gorges Hydropower Station, including thirty-two 700,000-kilowatt hydro-generator units, and two 50,000-kilowatt hydro-generator units. Its total installed capacity is as high as 22.5 million kilowatts, with an average annual power generation of more than 100 billion kilowatt-hours. It is the largest hydropower station on earth with the largest installed capacity. The second-ranked Itaipu hydropower station has a total installed capacity of only 14 million kilowatts. It is not a problem for a Three Gorges Dam to meet the power supply of a city. The average annual electricity consumption in Beijing is 114 billion kWh, and a Three Gorges Dam can meet the electricity consumption of the whole of Beijing for nearly a year. The annual electricity consumption of Chongqing, which is relatively close to the Three Gorges Dam, is also 118.6 billion kWh. It can be said that a Three Gorges Dam supports a mega city.
As the world's largest water conservancy project, the Three Gorges Dam has broken records in many of its engineering design indicators, and the cost of building the Three Gorges Dam is also very high. According to the calculation report of the National Audit Office of China, in the "Audit Results of the Draft Financial Final Accounts for the Completion of the Three Gorges Project on the Yangtze River" released by them, as of the end of December 2011, the total cost of the construction of the Three Gorges project was 207.873 billion yuan. In 2011, China's annual GDP was 7.55 trillion yuan, and the investment in the entire Three Gorges accounted for about 2.75% of China's annual GDP in 2011. Calculated at an average of 50 cents per kilowatt-hour of electricity, the Three Gorges can create economic benefits of 50 billion yuan every year, and it only takes 4 to 5 years to cover the original construction cost.
During the construction of the Three Gorges Project, some local residents also left the homes built by their parents and carried out large-scale immigration. These people also made their own contributions to the construction of the Three Gorges Project. During the construction of the Three Gorges Project, a total of nearly 1,296,400 people were relocated and 50,547,600 square meters of houses were relocated. This population size is equivalent to that of a medium-sized European country. Previously, the world's largest water conservancy project, Itaipu Power Station, emigrated. The number of people is about 46,000, and the population migration scale of the Three Gorges Dam is 28 times that of it! The Chinese people have a very strong attachment to their homeland, and it is difficult to leave their homeland. For the construction of the country's great power, the people of the Three Gorges Reservoir Area have left their homeland, which is also a commendable national righteousness.
The Three Gorges Project also facilitates the shipping of large ships. Before the Three Gorges impoundment, the annual one-way transport volume of the Yangtze River was only 10 million tons. Although the Yangtze River flows through Chongqing, the 10,000-ton ships cannot reach Chongqing, which greatly limits the transportation of cities along the river. Development, after the completion of the Three Gorges Dam, due to the increase in water level, the carrying capacity of the Yangtze River has also greatly increased. The Three Gorges Project has ended the history of "no night sailing since the ancient river", and ships of 10,000-ton class can also sail smoothly.
The Three Gorges Project also has some major impacts on the local ecological environment. The rise of the water level has formed large and small lakes in the local area. The number of various types of fish and wetland migratory birds has increased, the natural scenery has become more beautiful, and the local area has also changed. As a famous scenic tourist area, it was rated as the first batch of national 5A-level tourist attractions by the National Tourism Administration in 2007. If you have the opportunity, you must go to the Three Gorges Dam, feel the majesty of the motherland, and appreciate the Yangtze River. Beautiful scenery on both sides.
The Three Gorges Dam is built in the present, and its merits are in the future. As a national strategic project, it plays a huge role in improving people's livelihood, reducing natural disasters, utilizing water conservancy and power generation, and restoring a good ecological environment. It also embodies the efforts and wisdom of generations of Chinese people. A treasure in the history of people's development.