Beijing City Fortifications - Moats, Canals, and Other Watershed Systems

Moats, Canals, and Other Watershed Systems

The city of Dadu of the Yuan dynasty had an extensive moat system in and around the city. After Ming troops entered Dadu in 1368, the northern wall was rebuilt slightly south of the original. The new wall was constructed on the piled earthen hill formed from digging the moat of Dadu. A new moat system was built for the three main southern gates of the Palace, Imperial, and Inner city quarters. The three moats were then linked to the eastern and western moats of Dadu. When the Outer city was reconstructed during the Jiajing era (1521–1567), another moat was built surrounding the outer wall.

The water for the moats was spring water diverted from Mount Yuquan and Baifuquan, northwest of the city. The water followed Changhe and then split into two tributaries at Xizhimen. One route went east, forming the Inner city's moat system, and then divided into two further tributaries at Deshengmen, one flowing south, the other east. The other route entered at Jishuitan in the south, formed the three lakes of the imperial gardens, and finally rejoined the moat system at Tongzihe. From there the water flowed along the curvature of the city wall and joined the city's southern moat system at Zhengyangmen. The eastern route turned 90 degrees south at the northeastern corner guard tower and converged with the city's southern moat system to the northwest of Dongbianmen. Another moat flowed westwards and then southwards, forming the Outer city's moat system. It converged with the Inner city's southern and eastern moat systems at Dongbianmen, and finally entered the Tonghui River.

The Inner city's moat system was widest, at 30 to 50 metres, to the southeast of Zhengyangmen. The narrowest point, a mere 10 metres in width, was the section between Dongzhimen and Chaoyangmen. The moat was three metres deep at its deepest point, and a metre deep at its most shallow, near Fuchengmen. The outer moat was narrower and shallower than that of the Inner city. By the end of the Qing dynasty, the artificial moat system behaved no differently than a natural river system.

Water passageways located at several locations along Beijing's city walls helped permit the flow of the water supply into and out of the city. There were seven passageways in the Inner city: Deshengmen West (entered the Inner city, three passages), Dongzhimen South (left the city, one passage), Chaoyangmen South (left the city, one passage), Chongwenmen East (left the city, one passage), Zhengyangmen East (left the city, one passage), Zhengyangmen West (left the city, three passages), and Xuanwumen West (left the city, one passage). There were three passageways in the Outer city: Xibianmen East (entered the Outer city, three passages), Dongbianmen West (entered the Outer city, three passages), and Dongbianmen East (the main drainage for the inner and outer cities, three passages). The passageways had rammed earth foundations covered with stone slabs and stone bricks, followed by a layer of bricks. Each passageway had two or three layers of iron railings, and plenty of soldiers on guard.

The moat system influenced the daily activities of Beijing's commoners. From the Yongle era (1402–1424) until the mid-Qing dynasty (1644–1912), the eastern sections of the southern moat system were used as canals for the transportation of staple foods entering the city. Commoners could board boats at the eastern moat system, travel southwards to leave the city at Dongbianmen, and go down the Tonghui River, which leads to the rural areas of Tongzhou. Every year during the Hungry Ghost Festival, people would place small ships containing candles on the water. When frozen in winter, the moats were used as shortcuts in and out of the city. There would be skating, and the ice would be cut and saved underground for use in the summer months. The moats were home to many fish and ducks.

In 1953, Beijing's moat system was measured at 41.19 kilometres. As the city continued to expand, the moat system was no longer used, and much of it was channeled underground. The moat systems of the three main southern gates became underground rivers during the 1960s. The western, eastern, and northern moat systems were covered in the 1970s. A few remnants remain of the Inner city's northern moat system, the Outer city's southern moat system, and the imperial and Forbidden city's systems.

Many of Beijing's lakes were filled in during the mid-1960s to the mid-1970s (for example, Taiping Lake), totalling a land area of 33.4 hectares. Many others, such as Longxugou and Lianhuachi, were decreased in size by being partially filled in. The government also cleaned up many lakes outside of the city, making some into larger lakes. Public parks were created at Taoranting Park, Longtan Lake, Yuyuantan, and Zizhuyuan. Some new river systems were built during the 1950s (Kunyu River and Jingmi Diversion River).