Tracing Groundwater Recharge Sources Using Stable Isotopes

Dear Colleagues,

Identifying and quantifying groundwater recharge sources is one of the central challenges in hydrogeology. Historically, recharge assessments were based primarily on hydrological measurements, water balance calculations, and groundwater level fluctuations. However, these approaches often lack the resolution needed to resolve the origin, timing, and dynamics of recharge, especially in complex or data-scarce environments. Stable isotopes of oxygen (δ¹⁸O) and hydrogen (δ²H) have become standard tools for tracing the movement and source of water through the hydrological cycle. More recently, the application of additional isotopic systems—such as strontium (⁸⁷Sr/⁸⁶Sr), carbon (δ¹³C), and noble gases—has broadened the ability to characterize recharge processes, rock–water interactions, and aquifer connectivity. These advances have allowed researchers to assess recharge under changing climatic and land-use conditions, supporting more resilient water management strategies. Today, isotope hydrology is rapidly evolving. Researchers are integrating multiple tracers with geochemical modeling and remote sensing, improving temporal and spatial resolution. There is a growing demand to apply these tools to address pressing issues such as climate-driven recharge variability, groundwater depletion, and contamination risks.

Through this Special Issue, we aim to stimulate further innovation in the use of isotope tracers for groundwater recharge studies.

We expect the accepted articles to contribute to the following:

- refining conceptual models of recharge processes in diverse settings;

- quantifying recharge under non-stationary climate and land use;

- enhancing the resolution of recharge source discrimination using multi-isotope approaches;

- advancing the integration of isotopic, geochemical, and modeling tools.

The goal of this Special Issue is to gather original research articles and review papers that investigate isotope-based insights into aquifer recharge in both natural and anthropogenically influenced systems. Particular emphasis will be given to innovative applications and emerging methodologies that enhance our understanding of recharge dynamics across various climatic, geological, and land-use contexts. This topic lies at the intersection of isotope hydrology, hydrogeochemistry, and environmental modeling, and aligns closely with the interdisciplinary scope of Hydrology. Contributions that integrate isotopic tracers with numerical models, geochemical tools, or long-term monitoring strategies are especially encouraged.

This Special Issue will welcome manuscripts that explore the following themes:

- Applications of δ¹⁸O, δ²H, ⁸⁷Sr/⁸⁶Sr, and other tracers to identify recharge sources.

- Groundwater age-dating using noble gases and radioactive isotopes (³H, ¹⁴C, etc.).

- Rock–water interactions and their isotopic signatures.

- Isotopic tools in modeling recharge under different climatic and geologic settings.

- Assessing recharge in arid, semi-arid, coastal, and mountainous environments.

- Effects of land use, pollution, and climate change on recharge pathways.

- Novel tracer combinations and advances in sampling/analytical techniques.

We look forward to receiving your original research articles and reviews.

Dr. Stefania Da Pelo
Dr. Maria Chiara Porru
Dr. Wanjun Jiang
Guest Editors

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• groundwater recharge
• stable isotopes
• δ¹⁸O, δ²H, ⁸⁷Sr/⁸⁶Sr
• noble gases
• hydrogeochemistry
• isotope hydrology
• groundwater age dating
• rock–water interaction
• climate change impacts
• water resource sustainability