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Deciphering complex groundwater age distributions and recharge processes in a tropical and fractured volcanic aquifer system
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  • Ricardo Sanchez-Murillo,
  • Irene Montero-Rodríguez,
  • José Corrales-Salazar,
  • Germain Esquivel-Hernández,
  • Laura Castro-Chacón,
  • Luis Rojas-Jiménez,
  • José Vargas-Víquez,
  • Juan Perez Quezadas,
  • Esteban Gazel,
  • Jan Boll
Ricardo Sanchez-Murillo
Universidad Nacional de Costa Rica

Corresponding Author:[email protected]

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Irene Montero-Rodríguez
Universidad Nacional de Costa Rica
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José Corrales-Salazar
Universidad Nacional de Costa Rica
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Germain Esquivel-Hernández
Universidad Nacional de Costa Rica
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Laura Castro-Chacón
Empresa de Servicios Públicos de Heredia
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Luis Rojas-Jiménez
Empresa de Servicios Públicos de Heredia
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José Vargas-Víquez
Empresa de Servicios Públicos de Heredia
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Juan Perez Quezadas
Universidad Nacional Autonoma de Mexico Instituto de Geologia
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Esteban Gazel
Cornell University
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Jan Boll
Washington State University
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Abstract

Groundwater recharge in highly-fractured volcanic aquifers remains poorly understood in the humid tropics, whereby rapid demographic growth and unregulated land use change are resulting in extensive surface water pollution and a large dependency on groundwater extraction. Here we present a multi-tracer approach including δ18O-δ2H, 3H/3He, and noble gases within the most prominent multi-aquifer system of central Costa Rica, with the objective to assess dominant groundwater recharge characteristics and age distributions. We sampled wells and large springs across an elevation gradient from 868 to 2,421 m asl. Our results suggest relatively young apparent ages ranging from 0.0±3.2 up to 76.6±9.9 years. Helium isotopes R/RA (0.99 to 5.4) indicate a dominant signal from the upper mantle across the aquifer. Potential recharge elevations ranged from ~1,400 to 2,650 m asl, with recharge temperatures varying from ~11°C to 19°C with a mean value of 14.5±1.9°C. Recharge estimates ranged from 129±78 to 1,605±196 mm/yr with a mean value of 642±117 mm/yr, representing 20.1±4.0% of the total mean annual rainfall as effective recharge. The shallow unconfined aquifer is characterised by young and rapidly infiltrating waters, whereas the deeper aquifer units have relatively older waters. These results are intended to guide the delineation and mapping of critical recharge areas in mountain headwaters to enhance water security and sustainability in the most important headwater dependent systems of Costa Rica.
20 Aug 2021Submitted to Hydrological Processes
25 Aug 2021Submission Checks Completed
25 Aug 2021Assigned to Editor
25 Aug 2021Reviewer(s) Assigned
26 Sep 2021Review(s) Completed, Editorial Evaluation Pending
20 Oct 2021Editorial Decision: Revise Major
21 Dec 20211st Revision Received
22 Dec 2021Submission Checks Completed
22 Dec 2021Assigned to Editor
22 Dec 2021Reviewer(s) Assigned
02 Feb 2022Review(s) Completed, Editorial Evaluation Pending
04 Feb 2022Editorial Decision: Revise Minor
05 Feb 20222nd Revision Received
08 Feb 2022Submission Checks Completed
08 Feb 2022Assigned to Editor
08 Feb 2022Reviewer(s) Assigned
08 Feb 2022Review(s) Completed, Editorial Evaluation Pending
10 Feb 2022Editorial Decision: Accept