Stable isotopes reveal groundwater to river connectivity in a mesoscale subtropical watershed

ABSTRACT

The Corumbataí River basin (São Paulo, Brazil) has a critical situation regarding water availability due to the intensive use to support agriculture and urbanization, requiring scientific information to face water demand. The aim of this study is to present a hydrological characterization based on the analysis of seasonal isotope variations (rainfall, groundwater, and surface water) and hydrometric data. Results indicate that baseflow contribution varies from 50 % to 70 % of the total flow, and water isotopic composition denotes a seasonal regime marked by the mixing of surface and groundwater in the wet period and groundwater discharge during the dry season. The results presented indicated the strong seasonal connection between atmospheric inputs and water movement across the basin, which poses an urgent need to diversify monitoring methods and create feasible regional and political regulations to control the effects on basin water resilience in the face of climate change and growing demand.

KEYWORDS:

• Aquifer–river connectivity
• Corumbataí River basin
• deuterium excess
• groundwater recharge
• hydrogen-2
• isotope hydrology
• oxygen-18
• regional water management

Acknowledgements

We would like to thank Dr Gerhard Strauch, Editor in Chief of Isotopes in Environmental & Health Studies, and two anonymous reviewers for their valuable contribution to improve this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by a grant from the São Paulo Research Foundation (FAPESP) (Fundação de Amparo à Pesquisa do Estado de São Paulo) under Process 2018/06666-4, and funded by International Atomic Energy Agency [Grant CRP-19747], titled ‘Stable isotopes in precipitation and paleoclimatic archives in tropical areas to improve regional hydrological and climatic impact models’. First author (L.V.S.) and third author (V.S.) thanks FAPESP for the scholarship provided under the processes n° 2017/13576-9 and 2016/18735-5, respectively.