There is "Jinshui River, named after the Yuan Dynasty, named because it entered from the west gate" in the Annals of the Unification of the Qing Dynasty. The Yuan Dynasty called Jinshui River, which was named after the inflow from the west gate. According to the ancient five elements, the west belongs to gold, and the Yuan Dynasty called Jinshui River because the source of Jinshui came from the west. Compared with the Jinshui River in front of Tiananmen Square, it is called Neijinshui River.
So it can be seen that the inner gold water flows in from the west of the Forbidden City.
Extended data:
Neijinshui River not only beautifies the palace, but also provides water for fire prevention facilities of ancient buildings, and is also a sewer for palace drainage and rain. The palace covers an area of 720,000 square meters and has more than 90 courtyards, each with its own drainage channel. It uses the topography of high in the north and low in the south, discharges into the trench, flows into the Neijinshui River, and then leaves the palace along the river.
Baidu Encyclopedia-Neijinshui River