Is there another underground ring in Beijing? Uncover the secrets of this water supply loop in the capital →

This year marks the 10th anniversary of the opening of the middle route of the South-to-North Water Diversion Project. Over the past decade, more than 10.6 billion cubic meters of water from the south have flowed into Beijing, directly benefiting more than 16 million people. How is the water from the south distributed to thousands of households after it arrives in Beijing? The answer lies in a water supply loop in Beijing.

The so-called water supply loop is the underground water supply loop of the South-to-North Water Diversion Project in Beijing. Since 2014, in order to make full use of the "water from the south" and benefit more people, Beijing has gradually built an underground water supply loop along the North Fifth Ring Road, the East Fifth Ring Road, the South Fifth Ring Road, and the West Fourth Ring Road. It connects the West Fourth Ring Road culvert of the South-to-North Water Diversion Middle Route Main Canal, the Tuancheng Lake to the Ninth Water Plant Water Diversion Project, the South Canal Project and the East Canal Project, with a total length of about 107 kilometers.

The picture shows the main supporting projects of the South-to-North Water Diversion Project in Beijing. (Photo provided by Beijing Water Authority)

How does the water supply loop work? How to ensure the safety of urban water supply? With these questions, the reporter interviewed Wang Yan, senior engineer of the Operation Management Section of the Beijing South-to-North Water Diversion Loop Line Management Office, and Chang Peng, deputy section chief of the Dispatching Section.

According to reports, the main canal of the middle route of the South-to-North Water Diversion Project runs northward from the Danjiangkou Reservoir and intersects with the water supply loop at the Daning pressure regulating tank on the southwest side of the water supply loop. After this point, the "southern water" heading north will be "divided into two routes": one route runs from south to north, along the West Fourth Ring Road culvert to the Tuancheng Lake regulating tank in Haidian District. The other route leads to the South Canal Project and the East Canal Project, covering the southern and eastern areas of Beijing.

This is a photo of the Tuancheng Lake regulating pond in Beijing on November 10. Photo by Xinhua News Agency reporter Hu Jingwen

"Through these two routes, the coverage of 'southern water' entering Beijing has been expanded to the entire urban area, and it enters thousands of households through the supporting water plants we built," said Chang Peng.

If the "South Water" is cut off, how will the water supply loop operate? On the northwest side of the water supply loop, a water transmission line connects the Tuancheng Lake regulating pond and the Miyun Reservoir in northeastern Beijing. This water transmission line is the Miyun Reservoir Regulation Project.

Wang Yan introduced that the design of connecting the main canal of the South-to-North Water Diversion Project on one end and the Miyun Reservoir on the other end allows the water supply loop to supply water to major water plants, and also to transport water to the Miyun Reservoir through the Miyun Reservoir regulation project, storing precious "Southern Water". Once the "Southern Water" is cut off, the Miyun Reservoir can become an alternative water source for major water plants. In addition, there are ground projects such as the Yizhuang Regulating Pond on the water supply loop. In addition to directly supplying water to the Yizhuang Water Plant, this "big basin" located in the southeast of Beijing can also reversely transport the remaining water to the entire loop in an emergency to ensure water supply to the water plant.

The picture shows the Yizhuang Regulating Pond in southeast Beijing, taken on November 21. Photo by Xinhua News Agency reporter Tian Chenxu

"The water plants along the route now have 'multiple water sources' to guarantee their safety, which will help improve the water supply loop's ability to respond to water supply emergencies and ensure Beijing's water supply safety." Wang Yan introduced that in addition to ensuring the stability of the water supply, the South-to-North Water Diversion Project's Middle Route has also installed automatic monitoring and mobile monitoring equipment along the way, which can grasp the water quality in real time. Once an abnormality is found, the local water source can be switched to ensure water safety.

Staff members learn about the water quality of the Yizhuang regulating pond through the water quality monitoring system (photo taken on November 21, 2024). Photo by Xinhua News Agency reporter Tian Chenxu

Zhou Zheng, deputy director of the Water Supply Management Department of Beijing Water Authority, introduced that with the help of the water supply loop and other supporting projects of the South-to-North Water Diversion Project, "South Water" has become the main water supply source for Beijing, and the coverage of "South Water" has been continuously expanded, and the urban water supply safety factor has been increased from the original 1.0 to 1.3. At the same time, Beijing has also taken measures such as improving the treatment process of water plants and renovating old pipe networks to further ensure the water quality of "South Water" and improve the utilization efficiency of "South Water".

According to the Beijing Water Authority, this winter, the Daxing branch of Beijing's South-to-North Water Diversion Project has been fully filled with water, and is basically ready for water transmission. This water transmission line starts from the South Main Canal Project on the water supply loop in the north, spans across Daxing District in Beijing and connects to Gu'an County in Hebei Province.

"After the Daxing branch line is fully put into use, it will not only provide Beijing with another channel to receive 'water from the south', but also provide 'water from the south' for the Beijing New Airport Water Plant. More importantly, it can also realize two-way water transfer and mutual assistance of water sources between Beijing and Hebei. At that time, this water supply loop will be able to further expand the water supply scope of 'water from the south' and benefit more people." said Cao Haishen, deputy director of the Beijing South-to-North Water Diversion Loop Line Management Office.