Groundwater age, mixing and flow rates in the vicinity of large open pit mines, Pilbara region, northwestern Australia

摘要: Determining groundwater ages from environmental tracer concentrations measured on samples obtained open bores or long-screened intervals is fraught with difficulty because the sampled water represents a variety of ages. A multi-tracer technique (Cl, 14C, 3H, CFC-11, CFC-12, CFC-113 and SF6) was used to decipher production in regional aquifer around an pit mine Pilbara region northwest Australia. The changes due continuous dewatering over 7 years (2008–2014) were examined, methods compared. Tracer suggest that are mixture young old water; former inferred represent localised recharge adjacent creek, latter be diffuse recharge. An increase 14C activity time wells closest creek suggests achieve dry mining conditions has resulted change flow direction, so now forms larger proportion pumped groundwater. rate prior development, calculated steady-state Cl mass balance, 6 mm/y, consistent calculations based activity. Changes CFC-12 may related water-table position relative depth well screen.