Daecheong Dam

Back in 1968, South Korea was rapidly expanding and a strong focus on flood control and water supply emerged, resulting in an idea for a new dam in the stream area of the Keum river. Eventually, this led to the construction of the Daecheong dam, located between the cities Daejon and Cheongju (hence the name). In 1980 the dam was finished and became the third largest multipurpose dam in Korea: its main purposes are flood control, water supply, and hydropower generation. Today, dr. Deak Chun Han of K-water gave an extensive presentation about this the Daechong dam and showed us around afterward.

The dam costed 155.7 million US dollars to construct, largely paid for by the government. The basin area is approximately 4132 km2 and the dam height is 72m and 495 meters long (see figure 1 for an overview). The construction can be divided into two parts; the concrete gravity dam element and the embankment dam which consists of earth. A full concrete gravity dam was considered to be too heavy, and the possibility of soil subsidence was avoided by using different dam types.

Figure 1: overview of the Daecheong dam (scale model).

Reservoir capacity as a result of this enormous dam is 1,490,000000 m3 of water. The design flood level is 80m, and the high water level (full reservoir level) is 76.5m. At the moment of visiting the water reservoir was filled for approximately 66%, with a water level of 68m (see Figures 2 and 3 for an impression). This is normal for this moment of the year, the monsoon period has just passed and a period of less precipitation has begun. In case of excess water, the spillways can be opened. These 6 gates had an original maximum discharge of 10,452 m3/s. However, this has increased due to climate change threats and auxiliary spillways being added resulting in a total maximum capacity of 18,036 m3/s.

Figure 2: the lower river side of the Daecheong dam.
Figure 3: reservoir side of the Daecheong dam.

Two types of Frances turbines can deliver up to 90 MW in total. But the dam operates only 5 a 6 hours per day since this is not the only main purpose of the dam. The two generators can process approximately 100/200 m3/s per turbine which is a lot more than the normal discharge of 30 m3/s. To regulate the dam and fully use the potential of the turbines a smaller micro hydro powerplant is built downstream. This small dam with also hydropower turbines inside operates for 24 hours a day and ensures that the water outflow is equal to the normal, natural flow. In total the hydropower plant can generate 0.24 million kWh per year which is enough energy for 200,000 households. It takes roughly 5 minutes to turn on the electric power generation, so the dam is mainly used to relieve the peak of electricity demand in the morning.

The visit to the information center resulted in more detailed insight into the impact on the local environment. To store such tremendous amounts of water volume, approximately 26000 people had to migrate to other places. Most of the original houses are still there, only the large buildings have been demolished. Also, the wildlife is impacted, and fish cannot easily swim along the river. They are limited to the spillways, turbines, or weirs that open (see figure 4 for the spillways). The quality of the water itself is maintained by the combination of auto-warning systems, filtering ships, and algae protection measures

Figure 4: on the left the hydropower room and on the right the 6 spillways.

On top of the dam, one could experience the dam in all of its glory. Visual inspection of the internal structure of the dam and the room of the two hydropower turbines concluded the day. Despite the hydropower generation not being in motion at the time of visiting, walking through the concrete jungle along several pipelines, handles, and buttons for the operation of the dam showed the complexity of the dam. The Daecheong dam is a true feat of modern engineering.