The Beijing-Miyun Water Diversion Canal, abbreviated as Jingmi Diversion Canal, is a water diversion canal located within Beijing, China. It has a total length of 112.7 kilometers. Construction began in 1960, with the first phase completed in 1961 and the second phase finished in 1966. The project's primary goal is to divert water from the Chaobai River, stored in the Miyun Reservoir, into urban areas of Beijing. As the most important water supply route for the city, the Jingmi Diversion Canal is often said to deliver “two out of every three cups of water consumed daily by Beijing residents.”

Flow through The Jingmi Diversion Canal originates from the main dam of the Bai River at the Miyun Reservoir. It flows through the Huairou Reservoir and Kunming Lake in the Summer Palace, eventually joining the at Binjiao. The section from Kunming Lake to Binjiao, together with the stretch from Binjiao to Yuyuantan of the Yongding River Diversion Channel, is known as the . The Jingmi Diversion Channel passes through five districts of Beijing in sequence: Miyun District, Huairou District, Shunyi District, Changping District, and Haidian District.

History Construction of the Jingmi Diversion Canal began in 1960, and it started officially supplying fresh water to urban Beijing in 1961. The second phase of excavation began in 1966. In 1989, the channel began supplying fresh water to Beijing during the winter, transforming it from a seasonal water diversion system into a year-round water supply channel. Due to aging infrastructure and continuous overloading, large-scale repairs were carried out on the Jingmi Diversion Channel in 2005. The main work involved reinforcing the canal and removing silt. In 2009, taking advantage of the high water quality of the Guanting Reservoir in autumn, water delivery through the channel was suspended, and a renovation project was completed within 50 days.

Phase I Planning In 1958, the Beijing Municipal Committee ordered the Municipal Design Institute to begin designing a plan to divert water from the Miyun Reservoir into the Beijing-Miyun Canal. Initially, the plan had three main goals: first, to meet Beijing's domestic, industrial and agricultural water needs; second, to provide water for the Beijing-Tianjin Canal; third, to use artificial waterways to provide shipping capacity between Beijing's urban and suburban areas; fourth, to build a hydropower station in the canal and use the water flow to generate electricity; and fifth, to connect scenic spots such as Yuyuantan Park, Kunming Lake, Ming Tombs Reservoir, Miyun Reservoir and Xiaotangshan Hot Spring and use the canal to make these scenic spots form a tourist scenic belt and drive tourism development.

In the second half of the same year, the Municipal Design Institute began to organize staff to start planning and proposed a plan to the Beijing Municipal Party Committee. This plan was for the canal to start from the Miyun Reservoir Regulating Pool, flow southwest through the Hangezhuang Ship Lock in Miyun District, pass the Huairou Reservoir, reach Xicui Village, and flow through the tributaries of the Wenyu River. After that, it will flow out of Kunming Lake and flow to Luodaozhuang upstream of Yuyuantan Lake. Finally, it will merge with the Yongding River Diversion Channel and flow into the moat. After entering the moat, the canal will be divided into two parts, one of which will flow into the Qiansanmen moat, and the other will flow into the South moat, passing through Longtan Lake to Majuqiao in Tong County and merge with the Beijing-Tianjin Canal which is also under planning. In addition, the designers also planned a tributary, which starts from Xiaoxinfeng in Changping County (now Changping District), flows through , Qinghe, Dongzhimen and flows into the East moat.

To enable navigation, the plan included the construction of a ship lift below the Beibaiyan auxiliary dam of the Miyun Reservoir, allowing cruise ships to enter the reservoir. The section of the canal above Kunming Lake and below Longtan Lake was designated as the suburban navigation section, built to China's national Class III canal standard, allowing the passage of barges up to 1,000 tons or double-deck passenger vessels. The section between Kunming Lake and Longtan Lake was designated as the urban canal section, built to the national Class V standard, capable of accommodating barges up to 500 tons or single-deck passenger vessels. Based on Beijing's water needs at the time—for domestic, industrial, and agricultural use—the canal's designed flow rate was 100 cubic meters per second. The suburban section was planned to be 60 meters wide and 3 meters deep, while the urban section was 40 meters wide and 2.5 meters deep. The total volume of earthwork for the project reached 80 million cubic meters.

Design After the plan was approved by the Beijing Municipal Committee, the Municipal Design Institute began designing the water diversion project and appointed then-Deputy Chief Engineer Huang Zhendong as the chief designer. The first phase of the project started from the regulation pond of the Miyun Reservoir at Gongzhuangzi Village and ended at Xicuicun Village in Changping County, with a total length of approximately 53 kilometers.

The first phase of the design project is divided into four sections. The first section is from Gongzhuangzi Intake Gate to Huairou Reservoir. This section is about 25 kilometers long. The main project is to expand the existing Baihe Irrigation Canal. The design flow is 40 cubic meters per second, the channel bottom width is 8 meters, and the design water depth is 2.84 meters to 2.97 meters. The first 13 kilometers of this section is gravel as the bottom. In order to prevent water leakage, the design uses clay lining. The original design of this section required the water diversion tunnel of Huairou Reservoir, but the design flow of this tunnel was only 20 cubic meters per second, which could not meet the requirements of the Beijing-Miyun Canal. Therefore, the design team decided to open another outlet at Fengshan and build a new channel with a flow of 40 cubic meters per second. The second section starts from Xitaixia and ends at Lishishan Control Gate. It also uses the existing Baihe Irrigation Canal with the help of expansion. The design channel bottom width of this section is 10 meters, the design flow is 60 cubic meters per second, and the water depth is 3.1 meters. The third section starts from Lishishan and ends at the culvert of Xicui Village. It is 21.2 kilometers long, with a designed channel bottom width of 20 meters, a water depth of 3 meters, and a designed flow rate of 30 cubic meters per second. The fourth section starts from Xicui Village and ends at Dongbianmen. It is designed to be 37 kilometers long, with a channel bottom width of 20 meters and a flow rate of 30 cubic meters per second, but it was not constructed in the first phase of the project.

The head of the Beijing-Miyun Water Diversion Canal was located at Gongzhuangzi Village, 5 km downstream of the Baihe River main dam of the Miyun Reservoir. The head of the canal was designed with a regulating pond dam and a flood discharge gate. In addition, it was also equipped with a diversion canal water inlet gate, a ship lock and a hydropower station. The dam and flood discharge gate had already been built during the construction of the Miyun Reservoir, while the ship lock and the hydropower station were reserved and would not be built in the first phase of the project. Therefore, only the diversion canal water inlet gate remained to be built in the first phase of the project. This water inlet gate is a two-hole type with a 2.5m × 4.0m flat steel gate. The total height from the bottom of the gate is 86 meters. The design flow rate can reach 40 cubic meters per second, which was later changed to 50 cubic meters per second. A capacity of 100 cubic meters per second was reserved to prevent accidents.

In the design plan, the designers designed a water outlet gate at Fengshankou and a control gate at Lishishan, and planned to expand the water inlet gate of Huairou Reservoir. The design flow of Fengshankou water outlet gate is 40 cubic meters per second. After completion, it can allow ships with a maximum weight of 100 tons to enter Huairou Reservoir. The bottom elevation of the gate is 54.5 meters, the top elevation of the gate is 63.0 meters, the length of the gate chamber is 20 meters, the navigation water level is 59.2 meters, and the navigation clearance is 3.8 meters. The design flow of Lishishan control gate is 20 cubic meters per second. This gate serves as a water diversion gate. After the expansion, the water inlet gate of Huairou Reservoir will be upgraded from a two-hole type to a four-hole type, and will have a 2.3m×3.0m flat steel gate. In order to prevent flood accidents, two flood discharge gates were designed at and Taoyukou. The Yanqi Lake Flood Discharge Gate is located 1 km below the Beitaishang Reservoir Dam. The Beijing-Miyun Water Diversion Channel intersects with the mountain torrent ditch at this point, so a flood discharge gate was designed to be set up on the left bank of the channel. This flood discharge gate has two holes, a hole width of 6 meters, a gate bottom elevation of 57.0 meters, a 6m×5m arc-shaped steel gate, and a design flow of 155 cubic meters per second, which was changed to 231 cubic meters per second after calibration. The Taoyukou Flood Discharge Gate is designed as a 3-hole type, with a hole width of 6 meters, a gate bottom elevation of 47.82 meters, a 6m×5m arc-shaped steel gate, and a design flow of 239 cubic meters per second, which was changed to 388 cubic meters per second after calibration.

To allow certain sections of the Beijing-Miyun water diversion channel to pass beneath roads or riverbeds, the design plan included the construction of an inverted siphon. This siphon, known as the Shahe Inverted Siphon, is located 12.3 kilometers downstream from the Gongzhuangzi Intake Gate, and is named after the town of Shahe where it is situated. The siphon features a twin-barrel structure made of reinforced concrete, with each barrel measuring 3 meters by 3 meters. It has a total length of 131 meters and is designed for a flow rate of 40 cubic meters per second, with a flow velocity of 2.5 meters per second.Due to significant elevation differences along the canal route, the design team incorporated six drop structures (check dams) along the 9-kilometer section between the Gongzhuangzi Intake Gate and the Shahe Inverted Siphon. Each drop structure features a two-bay gate, 3 meters wide, with vertical drops ranging from 2.25 to 5.65 meters. Some of the larger drop structures were designed with space reserved for future hydropower stations.According to the design, wherever the canal passed through gullies with high sediment content or mountain streams with drainage areas between 10 and 50 square kilometers, culverts were constructed. In total, 25 culverts were designed along the entire Jingmi Diversion Channel. These culverts range from four-barrel to eight-barrel designs, and during dry periods, they can also accommodate vehicle traffic.To prevent overtopping and potential embankment failure caused by excessively high water levels, the designers included a side spillway 2 kilometers upstream from the Huairou Reservoir Intake Gate. Located on the left bank of the canal, the spillway has a canal bed elevation of 56.95 meters and a crest elevation of 59.65 meters. It is equipped with 13 sluice gates, each measuring 1.5 meters by 1.2 meters, using stacked beam gates.

Construction