Jinan, capital of east China's Shandong Province known as the country's "City of Springs," has employed cutting-edge technologies while building a subway network to ensure urban development does not come at the expense of its world-famous natural springs.
In addition to the three existing subway lines operating in areas relatively distant from the sensitive spring regions, Line 4 and Line 8 are currently in trial operation, while three additional lines are under construction in the city.
Relevant research shows that the springs in Jinan's urban areas originate from the southern mountains. The precipitation and surface runoff in the mountains penetrate deep into the ground and move northward into the city, forming some 1,000 natural springs, with Baotu Spring known as the finest one.
To map the invisible water channels underground and protect the springs, a team from the Shandong Provincial Bureau of Geology & Mineral Resources developed high-precision integrated geological survey technology.
"It's like giving the main karst groundwater channels a clear ultrasound scan," explained Zhao Zhiqiang, chief engineer of the team. "For the first time, we've identified and delineated these pathways in detail, laying the foundation for protecting the spring water flow channels."
When planning rail transit lines and selecting station sites, workers monitored the highest water level of springs in sensitive areas. The planned rail lines and stations were designed to remain above the highest water levels, maintaining a buffer distance of two to three meters, Zhao said.
Since Subway Line 4 passes through the core spring area, with its closest point only 1.4 km from Baotu Spring, engineers used a groundwater diversion system.
The technique adopts a "U-shaped pipe," redirecting groundwater under the construction site without blocking its path, Zhao said.
To further reduce the impact of subway construction on springs, the team also put forward a set of technical measures, such as directing subway lines away from areas sensitive to springs, keeping them clear of underground water-bearing layers, and reducing the depth of the tunnels. These measures have been used in the construction of several subway lines in the city.
According to Zhang Yunfeng, head of the team, their comprehensive protection approach has helped Baotu Spring maintain continuous flow for 22 years, demonstrating that modern infrastructure and natural springs can coexist.
Sources at the scenic area of Baotu Spring revealed that the spring's water level hit 30.29 meters as of Tuesday -- the highest recorded since 1966 -- driven by continuous rainfall since late September.
The team also developed a groundwater monitoring platform for spring protection across 213 locations, the first of its kind in north China.
Ma Hekuan, manager of the platform, said the system acts like a smart monitor for the springs, tracking the water levels, quality, extraction volume and replenishment volume in real time. It can trigger early warnings for centimeter-scale fluctuations in spring water levels 15 days in advance.
"The monitoring system for the springs, like a powerful 'CT scan,' has transformed groundwater management from guesswork to data-driven precision," Ma said.
