drainage of perivesical space

例句：

1. 1. The city's sewer system is responsible for the drainage of wastewater from residential areas.
   城市的下水道系统负责处理住宅区的废水。
2. 2. The construction of a new drainage system will greatly improve the water quality in the area.
   建设一个新的排水系统将大大改善该地区的水质。
3. 3. The draining of rainwater into the river is essential for maintaining the ecological balance of the river ecosystem.
   雨水流入河流是维护河流生态系统生态平衡的关键。