Groundwater evolution and mean water age inferred from hydrochemical and isotopic tracers in a tropical confined aquifer

The coastal confined aquifer in the Gulf of Urabá (Colombia) is an important water source for the banana agro‐industry as well as for urban and rural communities. However, the main processes controlling recharge and mixing in the aquifer are still poorly understood. Hydrochemical analyses and stable...

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Bibliographic Details
Published in:Hydrological processes 2018-07, Vol.32 (14), p.2158-2175
Main Authors: Villegas, Pedro, Paredes, Vanesa, Betancur, Teresita, Taupin, Jean D., Toro, Luis E.
Format: Article
Language:English
Subjects:
Aquifers
Carbon 14
Carbon dioxide
Carbonation
Cation exchange
Cation exchanging
Cations
Chemical composition
Climate
Climate change
Climatic conditions
Coastal aquifers
Colombia
Confined aquifers
confined coastal aquifer
Data
Depletion
Dissolved chemicals
Dissolved inorganic carbon
Earth Sciences
Environmental monitoring
Evolution
Geochemistry
Glacial periods
Groundwater
Groundwater age
Groundwater chemistry
Groundwater recharge
Hydrochemicals
Hydrology
isotope and geochemical hydrology
Isotopic tracers
mean groundwater ages
Modelling
Monitoring
Organic chemistry
Oxidation
Pleistocene
recharge areas and groundwater flow
Rural areas
Rural communities
Sciences of the Universe
Silicates
Stable isotopes
Tracers
Tropical climate
Water resources
Weathering
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Summary:The coastal confined aquifer in the Gulf of Urabá (Colombia) is an important water source for the banana agro‐industry as well as for urban and rural communities. However, the main processes controlling recharge and mixing in the aquifer are still poorly understood. Hydrochemical analyses and stable isotope monitoring were conducted to (a) determine groundwater recharge origin, mean groundwater age, and the main processes governing groundwater chemistry and the potential mixing of marine water and the influence of diffusive processes from the two surrounding aquitard layers. Hydrochemical data indicate that the main processes affecting the dissolved chemical composition include cation exchange, dissolution of carbonated and CO2, and silicate weathering. δ18O and δ2H compositions combined with 14C data highlight the differences in climatic conditions between the recharge zone and the confined section of the aquifer, which is close to the Atlantic Ocean. Groundwater samples with 14C ages from recent to 28,300 years BP show a depleted isotopic trend ranging from −6.43‰ to −9.14‰ in δ18O and from −43.2‰ to −65.7‰ in δ2H. The most depleted δ18O and δ2H compositions suggest a cooler recharge climate than the current conditions (corresponding to the last glacial period of the late Pleistocene). Depleted δ13C values in the total dissolved inorganic carbon indicate the existence of organic material oxidation processes within the geologic formation. These results can be used or transferred to enhance groundwater modelling efforts in other confined coastal aquifers of South America where scarcity of long‐term monitoring data limits water resources planification under a changing climate.
ISSN:0885-6087
1099-1085
DOI:10.1002/hyp.13160