At 8:00 on October 18, the water level of the Danjiangkou Reservoir successfully reached the normal storage level of 170 meters. This marks the third time the reservoir has reached this milestone water level since 2021 and 2023, indicating a dual victory in flood control during this year’s Han River autumn flood season and post-flood water storage. This achievement establishes a solid foundation for water supply to the Middle Route of the South-to-North Water Diversion Project and the middle and lower reaches of the Han River.

The weather conditions in the Han River basin during 2025 were particularly unusual. From January to August, rainfall and water inflow in the basin continued to be lower than average, with the Danjiangkou Reservoir’s water level once dropping below 150 meters, resulting in severe drought conditions. However, beginning on August 25 (8 days earlier than usual) with the start of the West China autumn rain period, the Han River basin experienced a historically rare “rapid transition from drought to flood.”

This autumn flood season exhibited four notable characteristics: long duration, lasting 55 days as of October 18; high rainfall intensity, with cumulative precipitation in the upper Han River reaching 573 mm, 2.8 times the multi-year average and ranking first since measurements began in 1961; numerous and closely spaced numbered flood events, with seven numbered floods occurring in sequence, including four floods (numbers 2 through 5) happening within 15 days, recognized as the “most concentrated autumn flood”; and large total flood volume, with the Danjiangkou Reservoir receiving approximately 29.7 billion cubic meters of water during the autumn flood season, about 2.7 times higher than the average for the same period, ranking second in the reservoir’s history since its completion in 1969.

Facing the severe autumn flood situation and demanding water storage tasks, the water authorities implemented scientific and precise regulation of the controlled reservoir system in the upper and middle reaches of the Han River, with the Danjiangkou Reservoir at its core.

By establishing a “forecast-warning-simulation-plan” working system and conducting over 80 flood regulation simulations using the digital twin Han River system, the scientific basis for decision-making was ensured. During this period, the water authorities issued 29 regulation orders to precisely control the Danjiangkou Reservoir’s outflow and storage process.

Throughout the autumn flood control period, the Han River basin reservoir system cumulatively retained 17.2 billion cubic meters of floodwater, with the Danjiangkou Reservoir alone retaining 12.7 billion cubic meters. Through scientific regulation, the main control stations in the middle and lower reaches of the Han River successfully avoided exceeding warning water levels, ensuring that the Dujiatai Flood Detention Basin and other flood diversion areas in the middle and lower reaches did not need to be activated. This effort prevented the flooding of 1.16 million mu of farmland, avoided the relocation of approximately 454,000 people, and reduced economic losses by about 11.14 billion yuan.

The successful filling of the Danjiangkou Reservoir to the 170-meter normal storage level is highly significant.

This not only indicates that flood control safety was ensured during the confrontation with the historically rare autumn flood but also that the end-of-flood-season water storage target was successfully achieved. As of October 18, the water storage in the upper Han River reservoir system had increased by approximately 17.8 billion cubic meters compared to before the autumn rains began, with the Danjiangkou Reservoir accounting for about 15 billion cubic meters of this increase. This provides a solid water source guarantee for the next year’s water supply to areas along the Middle Route of the South-to-North Water Diversion Project and the middle and lower reaches of the Han River.

Current safety monitoring data indicate that the Danjiangkou Reservoir dam is operating normally, and water quality remains stable and meets standards. Water authorities will continue to closely monitor rainfall and water conditions, implement coordinated regulation of water projects, and ensure the full utilization of the project’s comprehensive benefits.

Danjiangkou Reservoir

The Danjiangkou Reservoir is a large reservoir located on the Han River in Hubei Province, China. It was created in 1958 with the construction of the Danjiangkou Dam, primarily for flood control and hydroelectric power. The reservoir is also the source for the central route of China’s massive South-North Water Transfer Project, which required the relocation of hundreds of thousands of people.

Han River

The Han River flows through the heart of Seoul, South Korea, and has been a vital lifeline for over two thousand years, supporting early settlements and the kingdoms of Baekje and Joseon. In the 20th century, it became a central front in the Korean War and was later a symbol of the nation’s rapid economic development. Today, it is a major public recreation space, lined with parks, bike paths, and famous for its night cruises and modern light shows.

South-to-North Water Diversion Project

The South-to-North Water Diversion Project is a multi-decade Chinese infrastructure megaproject designed to channel water from the water-rich south to the arid north. It consists of three extensive canal systems—eastern, central, and western routes—to alleviate water shortages in northern cities, including Beijing. The ambitious project, with roots in a 1950s proposal, has involved the relocation of hundreds of thousands of people and has raised significant environmental and social concerns.

West China autumn rain period

The “West China autumn rain period” refers to a persistent rainy season occurring each September to October in western China, particularly the Sichuan Basin. This climatic phenomenon, historically documented for over a thousand years, is caused by moisture-laden air from the south meeting cold air from the north. The prolonged rainfall significantly influences regional agriculture and daily life while creating characteristically misty autumn landscapes.

Dujiatai Flood Detention Basin

The Dujiatai Flood Detention Basin is a key flood control facility located in Hubei Province, China, along the Yangtze River. It was historically used during major flood events, such as the severe 1998 Yangtze River floods, to divert excess water and protect densely populated downstream areas. Its operation involves intentionally inundating designated rural areas to prevent catastrophic flooding in major cities and critical infrastructure.

Middle Route of the South-to-North Water Diversion Project

The Middle Route of the South-to-North Water Diversion Project is a massive infrastructure system in China designed to channel fresh water from the Yangtze River basin in the south to the arid northern regions, including Beijing. Its construction, which began in 2003 and became operational in 2014, diverts water from the Danjiangkou Reservoir on the Han River. This project was conceived to alleviate chronic water shortages and support economic development in northern China.