Partitioning sources of recharge in environments with groundwater recirculation using carbon-14 and CFC-12

Sarah Bourke, Peter Cook, Shawan Dogramaci, Rolf Kipfer

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    Groundwater recirculation occurs when groundwater is pumped from an aquifer onto the land surface, and a portion of that water subsequently infiltrates back to the aquifer. In environments where groundwater is recirculated, differentiation between various sources of recharge (e.g. natural rainfall recharge vs. recirculated water) can be difficult. Groundwater age indicators, in particular transient trace gases, are likely to be more sensitive tracers of recharge than stable isotopes or chloride in this setting. This is because, unlike stable isotopes or chloride, they undergo a process of equilibration with the atmosphere, and historical atmospheric concentrations are known. In this paper, groundwater age indicators (14C and CFC-12) were used as tracers of recharge by surplus mine water that is discharged to streams. Ternary mixing ratios were calculated based on 14C and CFC-12 concentrations measured along three transects of piezometers and monitoring wells perpendicular to the creeks, and from dewatering wells. Uncertainty in calculated mixing ratios was estimated using a Monte Carlo approach. Ternary mixing ratios in dewatering wells suggest that recharge by mine water accounted for between 10% and 87% of water currently abstracted by dewatering wells. The calculated mixing ratios suggest that recharge by mine water extends to a distance of more than 550m from the creeks. These results are supported by seepage flux estimates based on the water and chloride balance along the creeks, which suggest that 85-90% of mine water discharged to the creeks recharges the aquifer and recharge by mine water extends between 110 and 730m from the creeks. Mixing calculations based on gaseous groundwater age indicators could also be used to partition recharge associated with agricultural irrigation or artificial wetland supplementation.

    Original languageEnglish
    Pages (from-to)418-428
    Number of pages11
    JournalJournal of Hydrology
    Volume525
    DOIs
    Publication statusPublished - 1 Jun 2015

    Keywords

    • Environmental tracers
    • Groundwater recharge
    • Hamersley Basin
    • Losing streams
    • Surface water-groundwater

    Fingerprint Dive into the research topics of 'Partitioning sources of recharge in environments with groundwater recirculation using carbon-14 and CFC-12'. Together they form a unique fingerprint.

  • Cite this