How does the Three Gorges Dam release floodwaters? The first peak shaving and flood discharge of the Three Gorges Dam in 2020

According to reports, on June 29th, in Yichang, Hubei, the Three Gorges Dam on the Yangtze River opened a deep hole for flood discharge. Recently, due to the continuous heavy rainfall in the upper reaches of the Yangtze River, the inflow of the Three Gorges Reservoir has increased. To ensure flood prevention safety, the Three Gorges Dam has launched deep hole flood discharge for the first time this year to adjust the water level of the reservoir.

How does the Three Gorges Dam release floodwaters?

Recently, the Three Gorges Dam located in Yichang, Hubei Province opened two deep holes to increase flood discharge, and the outflow volume has increased from around 25000 cubic meters per second to 35000 cubic meters per second. It is reported that before the opening of the two deep holes this time, the inflow of the Three Gorges Reservoir was 39000 cubic meters per second, and the water level was 147.51 meters, exceeding the flood control water level by 2.51 meters.

This has raised concerns among many people about whether the Three Gorges Dam's flood discharge will lead to flooding in the downstream areas of the Three Gorges Dam. In order to answer this question more clearly, let's first understand how the Three Gorges Dam discharges water?

We know,The Three Gorges Dam is a hydroelectric power station, and all the water is usually pumped out through generator sets to generate electricity. And flood discharge refers to the water in the reservoir flowing directly downstream from the dam without passing through the generator setAlthough the Three Gorges Dam is a hydroelectric power station, its most important function is not power generation, but flood discharge. Scientists have found that 80% of the water in the Yangtze River Basin is concentrated during the flood season, which is just one or two months.

Most of the rivers or tributaries in the Yangtze River Basin have limited water carrying capacity and cannot discharge the water during the flood season in a short period of time, which can lead to floods and waterlogging disasters.

The purpose of building the Three Gorges Dam is to collect water during the flood season in the upper reaches of the Yangtze River, which is equivalent to intercepting flood peaks and preventing floods from threatening the middle and lower reaches of the Yangtze River.

The total length of the Three Gorges Dam is 2308 meters and the total height is 185 meters, but the highest water level during floods is 175 meters, which can accommodate 39.3 billion cubic meters of floodwater. In normal times, the storage capacity of the Three Gorges Dam does not exceed 145 meters, which means there is a storage capacity of 30 meters to collect floods during the flood season.

During the flood season, if the water level of the Three Gorges Dam does not exceed 145 meters, the dam will not release floodwaters. If the water level exceeds 145 meters, the Three Gorges Dam will release floodwaters after the flood peak has passed. This is because the flood control design of the Three Gorges Dam is not to store floods for a long time, but to intercept the peak of floods in a short period of time and then slowly release them.

The Three Gorges Dam has a good regulatory effect on flood disasters in the downstream of the Three Gorges, ensuring the safety of people's lives and property to a certain extent. According to preliminary statistics and analysis by the Yangtze River Water Resources Commission, the joint operation of the Three Gorges and Qingjiang cascade reservoirs has successfully reduced the off peak flow of water from the upper reaches of the Yangtze River and the Qingjiang River flood, avoiding the water level exceeding the warning limit in the Jingjiang River section during this flood process.

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