An Imperial Hydraulic System
The Chengde Mountain Resort is a masterpiece of garden engineering, covering 5.6 million square meters, nearly half of Chengde's urban area. Its extensive water features are more than decorative; a functional, gravity-fed hydraulic system designed in the 18th century. Construction began in 1703 under Emperor Kangxi and continued for 89 years. The system's primary water source is the Wulie River, which flows along the resort's eastern edge.
Engineers diverted the river's water into the resort's network of lakes. A component of this system is the Rehe Spring, a natural spring that is the main source for the eight lakes within the resort and never freezes, even in winter. The initial lake system, including Lake Cheng, Ruyi Lake, Upper Lake, and Lower Lake, was excavated during the Kangxi era (1662–1722). The Qianlong Emperor (1736–1795) later expanded the network, adding Jing Lake and Yin Lake. The entire system relies on a subtle gradient to move water through the channels and into the lake district, which was designed to mimic the famous gardens of the Jiangnan region south of the Yangtze River.
Stone, Silt, and Scenery
The control and clarity of the water were paramount. The Qing engineers constructed a series of stone-lined channels, dykes, and sluice gates to manage flow, prevent stagnation, and direct water precisely where needed. These structures, built with traditional materials, allow operators to regulate lake levels and maintain the aesthetic quality of the water. The design also incorporated methods for managing silt. Over time, the canals that fed the lakes from the Wulie River filled with silt, a problem that required a major dredging project in the early 21st century to restore the original water flow.
The result of this hydraulic work is a series of interconnected lakes and islands that create a human-made area. The water system supports a lush environment for various plants and creates microclimates within the garden. Emperor Qianlong himself noted, "Though it is named Mountain Resort, its beauty is in water." Today, the system functions as it did for the Qing emperors, a sign of the durability and ingenuity of its original design. The resort was declared a UNESCO World Heritage Site in 1994.