Groundwater and surface water connectivity within the recharge area of Guarani aquifer system during El Nino 2014-2016

Autor(es)

Batista, Ludmila Vianna ^[1] ; Gastmans, Didier ^[1] ; Sanchez-Murillo, Ricardo ^[2] ; Farinha, Barbara Saeta ^[1] ; Rodrigues dos Santos, Sarah Maria ^[1] ; Kiang, Chang Hung ^{[1, 3]}

Afiliação do(s) autor(es)

^[1] Sao Paulo State Univ UNESP, Environm Studies Ctr, Av 24A, 1515 Bela Vista 13, BR-506900 Sao Paulo - Brazil

^[2] Natl Univ Costa Rica, Stable Isotope Res Grp, Heredia - Costa Rica

^[3] Sao Paulo State Univ UNESP, Dept Appl Geol, Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Hydrological Processes; v. 32, n. 16, p. 2483-2495, JUL 30 2018.
• Citações Web of Science: 3

Resumo

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 Jacare-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 Nino Southern Oscillation event. The large variation in the isotopic composition of precipitation (from -9.26 parts per thousand to +0.02 parts per thousand for O-18 and from -63.3 parts per thousand to +17.6 parts per thousand for H-2), mainly associated with regional climatic features, was not reflected in the isotopic composition of surface water (from -7.84 parts per thousand to -5.83 parts per thousand for O-18 and from -49.7 parts per thousand to +33.6 parts per thousand for H-2), mainly due to the monthly sampling frequency, and groundwater (from -7.04 parts per thousand to -7.76 parts per thousand for O-18 and from -49.5 parts per thousand to -44.7 parts per thousand for H-2), 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. (AU)

• Processo FAPESP: 15/15749-2 - Aplicação de isótopos estáveis na compreensão de processos no ciclo hidrológico: precipitação e pequenas bacias hidrográficas no estado de São Paulo, BR
• Beneficiário: Didier Gastmans
• Modalidade de apoio: Auxílio à Pesquisa - Regular