Fig. 3
Comparison of the (a) infiltration volume, (b) exfiltration volume and (c) scatter plot of exfiltration versus infiltration water volumes in various cities under different precipitation levels: LOW, MIDDLE and HIGH. *p < 0.05, ** p < 0.01, ***p < 0.001. Due to challenges in distinguishing exfiltrated from overflowed sewage, “exfiltration water volume per capita” (Vexf) here encompasses both exfiltrated sewage in dry periods and overflowed sewage during high flow events—total water per capita discharged externally from sewage network before reaching treatment plants. Square markings with an internal “X” denote cities with uncollected wastewater loads requiring attention.
