Which direction is the drainage flow of rural quadrangles?

Siheyuan is surrounded by houses with a yard in the middle. When it rains, due to the design of the courtyard roof, water will concentrate in the courtyard. There will be a water collecting basin or culvert in the central corridor, which will connect to the southeast corner and enter the urban culvert or open channel outside the quadrangle. Because the terrain of quadrangles is often high in the northwest and low in the southeast, water flows from the northwest to the southeast. In this way, the drainage function of the southeast corner is highlighted. Not only that, Beijing's drainage system also embodies this concept.

Because the whole water system in Beijing is closed from Jishuitan in the northwest and flows out from Tongjiang in the southeast, it just solves the drainage problem of urban construction.

Due to historical reasons, the quadrangles after New China have too many residents to form a complex, the infrastructure is scrapped, and the drainage system cannot be used normally, forming a dead corner, which restricts the living environment of quadrangles.

Modern new quadrangles and rebuilt quadrangles all focus on drainage and exhaust sanitation, and are connected with modern equipment, professional sewer system and water supply system, and connected with urban tap water pipelines. But the cost is still relatively high …