@article{fdi:010072812,
  title = {{G}roundwater flowpaths and residence times inferred by {C}-14, {C}l-36 and {H}e-4 isotopes in the {C}ontinental {I}ntercalaire aquifer ({N}orth-{W}estern {A}frica)},
  author = {{P}etersen, {J}. {O}. and {D}eschamps, {P}ierre and {H}amelin, {B}. and {F}ourre, {E}. and {G}oncalves, {J}. and {Z}ouari, {K}. and {G}uendouz, {A}. and {M}ichelot, {J}. {L}. and {M}assault, {M}. and {D}apoigny, {A}. and {A}ster, {T}eam},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n a semi-arid to arid climate context, dependency on groundwater resources may lead to overexploitation and deterioration of water quality. {T}he {C}ontinental {I}ntercalaire ({CI}) aquifer is one such continentalscale aquifer (more than a million of km(2)), which is mainly confined, poorly recharged but intensely abstracted. {T}o date, the management of this resource relies on hydrogeological modelling and key parameters such as recharge/discharge rate and groundwater dynamics. {W}e use a combination of residence time indicators ({C}-14, {C}l-36, {H}e-4) and stable isotopes of water ({H}-2 and {O}-18) to give greater constraint on the groundwater residence time in the {CI}. {I}n previous studies, {C}-14 measurements and steady state modelling indicate a residence time of less than 100 ka whereas in others, {C}l-36 measurements and transient scenarios modelling suggest a longer residence time (>500 ka). {I}n this study, most of the {C}-14 measurements are below the limit of detection, establishing residence times greater than 40 ka and confirming the necessity of strict sampling protocols to exclude all air and {AMS} measurements when low {C}-14 concentrations are expected. {I}n the {T}unisian recharge area, detectable {C}-14 indicate sporadic recharge episodes (3-7 ka and 29-43 ka), whereas {H}e-4 and {C}l-36 concentrations in central areas suggest very old (<2 {M}a) groundwaters. {I}n these central areas, chlorine concentration can reach more than 2 g/l. {S}ince {C}l-36 concentrations are up to 4 time less than the initial input, we are confident there is no excessive deep {C}l-36 production. {W}e characterise five distinct flowpaths reaching the {T}unisian discharge area using their isotopic signatures. {A}ccording to our mixing model, the average contribution from the main recharge area, the {A}lgerian {A}tlas {M}ountains, is around 88%. {T}his value is close to hydrogeological models. {C}onversely, the contribution from the {D}ahar {M}ountains is lower than in the hydrogeological modelling (2% against 10%) whereas the {T}inhert shows a greater contribution (10% against 1%). {I}ncrease of abstraction from the {CI} can potentially activate the circulation of old brackish groundwaters and dramatically decrease the water quality in the whole system.},
  keywords = {{R}echarge ; {G}roundwater budget ; {R}adioactive isotopes ; {S}tables isotopes ; {C}ontinental-scale aquifer ; {T}unisia and {A}lgeria ; {TUNISIE} ; {ALGERIE}},
  booktitle = {},
  journal = {{J}ournal of {H}ydrology},
  volume = {560},
  numero = {},
  pages = {11--23},
  ISSN = {0022-1694},
  year = {2018},
  DOI = {10.1016/j.jhydrol.2018.03.003},
  URL = {https://www.documentation.ird.fr/hor/fdi:010072812},
}