Multi-Evidence Identification of Distinct Recharge–Discharge Systems Across the F2 Fault: A Case Study of the Chunjingwa Closed Coal Mine, China

Determining the recharge sources of adjacent old-working water outlets and their hydraulic connections is essential for zoned pollution control in closed coal mines. This study examined two outlets, S1 and S2, 174 m apart in the Chunjingwa closed coal mine area, Shanxi Province, China. Discharge dynamics, hydrochemistry, hydrogen–oxygen stable isotopes, and a goaf pumping test were combined. During natural monitoring, discharges at S1 and S2 ranged from 1.172–1.958 and 1.012–8.630 m3/h, respectively, with the variation at S2 (7.618 m3/h) being 9.7 times that at S1 (0.786 m3/h). Most contamination indicators had higher median exceedance levels at S2; for SO42−, the median was 14.6 at S2 versus 8.4 at S1. Isotopically, S1 overlapped with ZK2 and ZK3, whereas S2 was distinct. During the 27-day pumping test, S1 discharge fell by about 91%, whereas S2 showed no clear response. The evidence identifies two distinct recharge–discharge systems on opposite sides of F2 at the tested scale. F2 is interpreted as a structural divide, not a uniformly impermeable fault. S1 is regulated mainly by goaf-water storage to the south, whereas S2 is dominated by shallow-catchment, rapid-infiltration recharge to the north. The framework provides a practical alternative to artificial tracer tests for outlet-scale source identification and zoned remediation.