Beijing's thirst for water quenched

Water from the south via major national diversion project a lifeline for the city

Over the past decade, the middle route of China's South-to-North Water Diversion Project has transferred more than 10.6 billion cubic meters of water from the country's water-rich central and southern regions to Beijing, the drought-prone national capital.

The middle route of the mega project was put into operation in December 2014. It channels water from Central China's Danjiangkou Reservoir to Beijing, Tianjin and Hebei province.

Out of the 10.6 billion cubic meters of water diverted to Beijing, approximately 7 billion cubic meters were allocated for domestic use, benefiting over 16 million residents. This amount accounts for nearly 80 percent of the urban areas' water usage.

The introduction of water from the south has increased Beijing's annual water supply per capita from 100 to 150 cubic meters, enhancing the utilization and conservation of the city's water resources.

A watershed moment

Once rich in water resources, Beijing had endured more than a decade of drought since 1999. The lack of water, coupled with rapid urbanization and population growth, led to overexploitation of local water resources, which resulted in a continuous decline in groundwater levels.

The introduction of southern water in 2014 provided Beijing's overdrawn groundwater with a much-needed respite, marking a turning point where groundwater levels stopped declining and began to rise.

Southern water has since been incorporated as a fifth water source for the city, alongside surface water, groundwater, rainwater and reclaimed water.

The Miyun Reservoir in northeastern Beijing, the primary source of surface water for consumption in the city, experienced deficits during those dry years. Since 2014, water diverted from the south has replaced the reservoir as the main water source for residents, enabling the reservoir to replenish.

In 2015, the water level of the Miyun Reservoir stopped declining, and with reduced water withdrawals and the addition of the diverted water, the reservoir's water level began to increase.

The water storage of the Miyun Reservoir had reached 3.58 billion cubic meters by October, marking a record high in the reservoir's more than 60 years of existence. In 2013, the figure was only around 800 million cubic meters.

Groundwater levels in Beijing's plain areas have been rising for nine years, with a cumulative increase of 13.68 meters. The groundwater reserves have increased by 7 billion cubic meters compared with that of 2015.

With the arrival of the water from the south of the country, 81 springs in Beijing have been replenished. Water flow has been restored to the city's Yongding River, Chaobai River, Beiyun River, Juma River and Juhe River for the first time in decades.

Seamless transition

Can the southern water coexist with the local water? The answer to this question can be found at Beijing's largest surface water plant — the Ninth Water Plant of Beijing Waterworks Group.

At the plant, the blend of the southern water and local water undergoes conventional treatment processes such as sedimentation and disinfection, as well as advanced processes including ozone treatment and ultrafiltration. These processes produce tap water that meets or exceeds the national standards for drinking water quality.

The plant initially blended the southern water with water from the local Miyun Reservoir at a ratio of one to four, but it has gradually increased the proportion of southern water over time.

"Both the water from the Miyun Reservoir and the water diversion project are high-quality surface water. However, considering their distinct geographical origins, we were concerned that residents might be uncomfortable with an abrupt change," explained Wang Yue, deputy director of the plant, according to a Beijing Daily report.

Given the different construction periods and materials of Beijing's water supply network, Beijing Waterworks Group established a testing base in the Danjiangkou Reservoir, the source of the South-to-North Water Diversion Project, in 2011 to facilitate a seamless transition between the diverted southern water and the local water.

The water department sent representative pipelines from Beijing to Danjiangkou for adaptation tests. Meanwhile, tap water produced at the testing base in Danjiangkou was transported to 20 locations within Beijing's water supply network for adaptation studies.

Given that the southern water is transported through open canals and may contain higher algae content due to strong sunlight, the Ninth Water Plant has optimized its pretreatment processes. For instance, it has incorporated ozone treatment to adjust to the characteristics of southern water and to ensure consistent water quality.

The Guanxizhuang Pumping Station in Beijing intercepts debris such as leaves from the southern water before sending it to the Ninth Water Plant. The station utilizes artificial intelligence-powered automatic algae-monitoring devices developed by a local research institute, which are capable of detecting changes in the quantity and types of algae in the southern water.

Zhang Lei, a senior engineer at the Beijing Water Science and Technology Institute, told Beijing Daily that traditionally algae monitoring was done manually, which took at least 48 hours. In contrast, the AI monitoring device is able to complete the process in only 20 minutes.

Smart management

Beijing has optimized its water management strategies upon receiving the southern water. On the one hand, it has increased the allocation of southern water for daily consumption and industrial use, reducing reliance on local groundwater and extraction from local sources. On the other hand, the city has decreased water withdrawals from the Miyun Reservoir and stored excess southern water in the reservoir.

With the addition of southern water, Beijing has linked the Miyun and Huairou reservoirs via diversion projects, replenishing groundwater sources through rivers including the Yongding River and Chaobai River.

To bolster water supply security, Beijing has built a 107-kilometer underground water supply loop to support the South-to-North Water Diversion Project, enabling the coordinated distribution of the southern water, water from the Miyun Reservoir and groundwater.

Wang Yan, a senior engineer with the administrative agency of the loop, told Beijing Daily: "In the event of a water supply disruption from the South-to-North Water Diversion Project, we can switch the water source from the project to the Miyun Reservoir. This ensures a continuous water supply to the water plants along the loop, providing them with a backup water source."

In recent years, Beijing has renovated over 1,000 km of pipelines, replaced more than 4.5 million remote water meters, and adopted new technologies such as satellite detection for identifying and fixing leaks.

Since the arrival of the southern water, the leakage rate in Beijing's water supply network has decreased by 4.3 percentage points, leading to annual water savings of over 40 million cubic meters.

In addition to safer supplies, Beijing has prioritized water conservation and optimized its industrial structure to efficiently utilize the water from the south.

The city has made significant efforts to conserve water used in daily life, agriculture, industrial production, landscaping and public services. It has been advancing initiatives such as sponge city construction, wastewater reuse and urban water ecosystem restoration.

Beijing has been a national leader in terms of water usage for every 10,000 yuan ($1,374) of regional GDP and that for every 10,000 yuan of industrial added value. In March 2023, the city introduced a set of regulations on water conservation, which aim to establish a water-saving system that covers the entire water utilization process.

huyuyan@chinadaily.com.cn