Tracing groundwater dynamics in the Chakari Basin, Afghanistan: A multi-tracer study with socio-environmental implications

Abstract

Study regionThe Chakari Basin in southeastern Kabul, Afghanistan, is an arid to semi-arid region where groundwater from springs, wells, and karezes serves as the primary water resource. Despite its importance, the hydrogeological characteristics of the basin, including groundwater origin, flow pathways, and age, remain poorly constrained due to long-standing infrastructural, technical, and socio-political limitations.Study focusThis study applies a comprehensive multi-tracer approach to overcome these data gaps and evaluate groundwater dynamics in the Chakari Basin. We analyzed stable isotopes (δ²H, δ¹⁸O), radioactive tracers (³H, ¹⁴C), anthropogenic atmospheric trace gases (CFC-11, CFC-12, CFC-113, SF₆), and noble gases (⁴He, ²²Ne) to identify recharge sources, quantify groundwater residence times, and assess mixing processes and anthropogenic influences. The integrated dataset provides the first systematic assessment of groundwater age and recharge conditions for the basin.New hydrological insightStable isotope compositions indicate meteoric recharge originating from relatively high elevations. CFC-based groundwater ages of approximately 10–40 years reveal that a substantial fraction of the basin’s groundwater reflects multi-decadal recharge. Several tracers showed region-specific limitations, including anomalously high SF₆ likely linked to recent atmospheric contamination, dilution of ¹ ⁴C activity by carbonate dissolution, and mostly non-detectable ³H consistent with older or deeper flow components. Noble gas excesses, particularly ²²Ne, corroborate the multi-decadal residence times and indicate partial mixing along flow paths. These findings provide the first integrated groundwater age framework for the Chakari Basin and highlight the value of tracer cross-validation for robust hydrogeological interpretation in regions facing climatic stress, rising water demand, and vulnerability to contamination.