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Groundwater and surface water connectivity within the recharge area of Guarani aquifer system during El Niño 2014–2016
Author(s) -
Batista Ludmila Vianna,
Gastmans Didier,
SánchezMurillo Ricardo,
Farinha Bárbara Saeta,
Santos Sarah Maria Rodrigues,
Kiang Chang Hung
Publication year - 2018
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.13211
Subject(s) - groundwater recharge , groundwater , aquifer , baseflow , hydrology (agriculture) , surface water , infiltration (hvac) , environmental science , precipitation , geology , water balance , drainage basin , streamflow , geography , geotechnical engineering , cartography , environmental engineering , meteorology
Recharge areas of the Guarani Aquifer System (GAS) are particularly sensitive and vulnerable to climate variability; therefore, the understanding of infiltration mechanisms for aquifer recharge and surface run‐off generation represent a relevant issue for water resources management in the southeastern portion of the Brazilian territory, particularly in the Jacaré‐Pepira River watershed. The main purpose of this study is to understand the interactions between precipitation, surface water, and groundwater using stable isotopes during the strong 2014–2016 El Niño Southern Oscillation event. The large variation in the isotopic composition of precipitation (from −9.26‰ to +0.02‰ for δ 18 O and from −63.3‰ to +17.6‰ for δ 2 H), mainly associated with regional climatic features, was not reflected in the isotopic composition of surface water (from −7.84‰ to −5.83‰ for δ 18 O and from −49.7‰ to +33.6‰ for δ 2 H), mainly due to the monthly sampling frequency, and groundwater (from −7.04‰ to −7.76‰ for δ 18 O and from −49.5‰ to −44.7‰ for δ 2 H), which exhibited less variation throughout the year. However, variations in deuterium excess ( d ‐excess) in groundwater and surface water suggest the occurrence of strong secondary evaporation during the infiltration process, corresponding with groundwater level recovery. Similar isotopic composition in groundwater and surface water, as well as the same temporal variations in d ‐excess and line‐conditioned excess denote the strong connectivity between these two reservoirs during baseflow recession periods. Isotopic mass balance modelling and hydrograph separation estimate that the groundwater contribution varied between 70% and 80%, however, during peak flows, the isotopic mass balance tends to overestimate the groundwater contribution when compared with the other hydrograph separation methods. Our findings indicate that the application of isotopic mass balance methods for ungauged rivers draining large groundwater reservoirs, such as the GAS outcrop, could provide a powerful tool for hydrological studies in the future, helping in the identification of flow contributions to river discharge draining these areas.