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Prof. Dr. Oliver Schilling

Department of Environmental Sciences
Profiles & Affiliations

My research aims at improving our understanding of surface water-groundwater interactions in diverse environments. I'm particularly interested in the development and application of novel tracer methods for this purpose and integration of these data into fully coupled surface water-groundwater model calibration. We're currently working on the implementation of multiple in situ online tracer monitoring techniques (e.g., for noble gases and microbes) and data assimilation procedures.

Selected Publications

Musy, Stephanie L., Dresmann, Horst, Tomonaga, Yama, Sano, Yuji, & Schilling, Oliver S. (2025). Modeling a geologically complex volcanic watershed for integrated water resources management in Mt. Fuji, Japan [Journal-article]. Scientific Data. https://doi.org/10.1038/s41597-025-06380-z

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Currle, Friederike, Therrien, René, & Schilling, Oliver S. (2025). Explicit simulation of microbial transport with a dual-permeability, two-site kinetic deposition formulation using the integrated surface–subsurface hydrological model HydroGeoSphere. Hydrology and Earth System Sciences, 29(20), 5383–5403. https://doi.org/10.5194/hess-29-5383-2025

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van Tiel, Marit, Aubry-Wake, Caroline, Somers, Lauren, Andermann, Christoff, Avanzi, Francesco, Baraer, Michel, Chiogna, Gabriele, Daigre, Clémence, Das, Soumik, Drenkhan, Fabian, Farinotti, Daniel, Fyffe, Catriona L., de Graaf, Inge, Hanus, Sarah, Immerzeel, Walter, Koch, Franziska, McKenzie, Jeffrey M., Müller, Tom, Popp, Andrea L., et al. (2024). Cryosphere–groundwater connectivity is a missing link in the mountain water cycle [Journal-article]. Nature Water, 2, 624–637. https://doi.org/10.1038/s44221-024-00277-8

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Epting, Jannis, Raman Vinna, Carl Love, Affolter, Annette, Scheidler, Stefan, & Schilling, Oliver S. (2023). Climate change adaptation and mitigation measures for alluvial aquifers - Solution approaches based on the thermal exploitation of managed aquifer (MAR) and surface water recharge (MSWR). Water Research, 238, 119988. https://doi.org/10.1016/j.watres.2023.119988

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Schilling, O. S., Nagaosa, K., Schilling, T. U., Brennwald, M. S., Sohrin, R., Tomonaga, Y., Kipfer, R., Brunner, P., & Kato, K. (2023). Revisiting Mt. Fuji’s groundwater origins with helium, vanadium and eDNA tracers. Nature Water, 1, 60–73. https://doi.org/10.1038/s44221-022-00001-4

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Selected Projects & Collaborations

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Slow Water

Research Project  | 11 Project Members

English:

Mountainous countries like Switzerland are overproportionally affected by climate change, with temperature rise and increasing weather extremes such as heat waves, droughts, and torrential rainfalls already being more pronounced than elsewhere. Under these circumstances, water supply is becoming a major challenge for agriculture, be it for crop production or animal husbandry. In addition, water in mountain communities becomes increasingly scarce during summer months. This is where the Swiss Federal Office of Agriculture FOAG-funded "Slow Water" project comes in: In 3 hydrologically and geographically distinct pilot regions of Switzerland, farm-specific, catchment-related water retention strategies are developed and implemented based on a catalogue of 15+ different nature-based water retention measures, through a co-creation process involving municipalities, farmers, authorities and scientists. The integral impacts of the nature-based water retention measures on increasing water availability and decreasing streamflow extremes are assessed through a combination of hydrological monitoring, drone-based assessments and numerical modelling. The Slow Water project consortium consists of the Hydrogeology research group of University of Basel and Eawag, the Global Land Use and Change group of University of Basel, the agricultural offices of the Cantons of Basel-Landschaft (Ebenrein) and Luzern (LAWA), Seecon GmbH, Agridea, municipalities and farming associations.


Deutsch:

Alpenländer wie die Schweiz sind überproportional vom Klimawandel betroffen, und der Temperaturanstieg und zunehmende Wetterextreme wie Hitzewellen, Dürren und Starkregenereignisse sind hier bereits jetzt ausgeprägter als anderswo. Unter diesen Umständen wird die Wasserversorgung zu einer grossen Herausforderung, insbesondere auch für die Landwirtschaft, sei es für den Pflanzenbau oder die Tierhaltung. Darüber hinaus wird Wasser in Gemeinden ohne Anschluss an grössere Grundwasservorkommen, Flüsse oder Seen, was typisch ist für Berggemeinden, während der Sommermonate zunehmend knapp. Hier setzt das vom Bundesamt für Landwirtschaft BLW finanzierte Ressourcenprojekt «Slow Water» an: In drei hydrologisch und geografisch unterschiedlichen Pilotregionen der Schweiz werden auf der Grundlage eines Katalogs von mehr als 15 verschiedenen kleinskaligen, naturbasierten Wasserrückhaltemassnahmen in einem ko-kreativen Prozess unter Einbezug von Gemeinden, LandwirtInnen, Behörden und WissenschaftlerInnen betriebs- und einzugsgebietsspezifische Wasserrückhaltestrategien entwickelt und Massnahmen umgesetzt. Die integralen Auswirkungen der naturbasierten Wasserrückhaltemassnahmen auf die Erhöhung der Wasserverfügbarkeit und die Verringerung von Extremabflüssen werden durch eine Kombination aus hydrologischer Überwachung, drohnenbasierten Analysen und numerischer Modellierung bewertet. Das Konsortium des «Slow Water»-Projekts besteht aus der Forschungsgruppe Hydrogeologie der Universität Basel und der Eawag, der Forschungsgruppe Globale und regionale Landnutzungsänderungen der Universität Basel, den landiwrtschaftsämtern der Kantone Basel-Landschaft (Ebenrein) und Luzern (LAWA), Seecon GmbH, Agridea, Gemeinden, und Landwirtschaftsverbänden.

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Sustainable nitrogen fertilization for agricultural crops developed based on open lab and field experiments with integrated hydrological modelling in near-real-time

Research Project  | 5 Project Members

Humanity has reached a point where the capacity to live without irreversibly compromising Earth’s resources is questioned. Since the 1980s, both Earth’s population and global food production have been constantly increasing. To face the challenges of increasing food and water demand, agricultural production efficiency must be improved. Initiatives like the UN Sustainable Development Goals (SDGs) describe major challenges for clean water and food production. Accordingly, food production and access to clean water must be a priority in the context of sustainable development. To tackle these important challenges to sustainable development, the present project will build on a combination of agricultural field and integrated hydrological modelling experiments. The knowledge obtained in the field and modelling experiments will be ultimately combined to enable the creation of a prototype near-real time decision support tool for sustainable and resilient management of nitrogen fertilization.


In Poland, cereal production is a major component of the national economy. Even though fertilizer use has been restricted since 2017, in 2020 the Polish government still reported a significant trend of increasing nitrogen concentrations in water bodies. Climate change makes agricultural production even more vulnerable and challenging, pushing farmers to overfertilization. Given the fact that 30% of Polish agricultural soils consist of soils highly prone to fertilizer leaching, it comes as no surprise that excessive nutrient loadings are still widely observed. Due to its high mobility, the most applied agricultural fertilizer Nitrogen (N) is the most prone to leaching, and as a result, N (primarily in the form of nitrate) is by far the most widely observed agricultural contaminant in water bodies worldwide, including in Poland and Switzerland.


To tackle these important challenges to sustainable development, the project will build on a combination of field and modelling experiments. The Swiss project partner will focus on the integrated simulation of hydrological fluxes, crop dynamics and nitrogen-cycling. The Polish project partner will focus its research on field experiments in agricultural fields and in the university's outdoor agricultural laboratory. The knowledge obtained in the field and modelling experiments will be ultimately combined to enable the creation of a prototype near-real time decision support tool for sustainable and resilient management of nitrogen fertilization.

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Development of a membrane inlet system for in-situ and continuous monitoring of noble and greenhouse gas fluxes in snowpacks & soils with a portable mass spectrometer system

Research Project  | 2 Project Members

A crucial element in better understanding climate change and its impact on hydrological, biogeochemical and ecosystem dynamics lies in the accurate monitoring of hydrological and biogeochemical processes. Most available analytical techniques for the measurement of (greenhouse) gases in the environment, however, are either laboratory based or based on instrumentation that is built for in-field applications in warm and temperate climates. In (sub)polar and high-altitude regions, existing analytical techniques face significant challenges related to the very cold and typically harsh weather. Currently, there is no existing system to measure the (greenhouse) gas concentrations and fluxes all the way from the subsurface, through soils, water bodies and snowpacks, to the atmosphere in very cold environments. With this SPI Technogrant, we will develop a new membrane system for continuous and automated measurements of the gas composition of interstitial air in snowpacks and soils as well as in surface waters and groundwaters in sub-arctic to arctic environments. The new system will extend a recently developed portable gas equilibrium-membrane inlet mass spectrometer (GE-MIMS), a breakthrough technology for the on-site and near real-time, continuous measurement of 4 He, 40 Ar, 84 Kr, N 2 , O 2 , CO 2 , CH 4 and H 2 in air and dissolved in water [1]. Our new extended gas monitoring system will, for the first time, enable continuous and autonomous on-site monitoring of greenhouse gas fluxes, sources and sinks in and through soils, snowpacks, surface water and groundwater in subarctic to arctic regions, thus providing a critical missing piece in the global greenhouse gas puzzle. The new system will be assembled and systematically tested at the University of Basel, and subsequently implemented in collaboration with Oulu University and the Finnish Meteorological Institute for continuous and automated in-situ monitoring of noble and greenhouse gases in snowpack, soils, groundwater, and surface water at the largest atmosphere watch site of the circumpolar region, the Pallas atmosphere-ecosystem super site [2]. References [1] Brennwald et al. (2016). A portable and autonomous mass spectrometric system for on-site environmental gas analysis. Environ. Sci. Technol., 50, 13455-12463. https://doi.org/10.1021/acs.est.6b03669 [2] Marttila et al. (2021). Subarctic catchment water storage and carbon cycling - Leading the way for future studies using integrated datasets at Pallas, Finland. Hydrol. Process., 35, e14350. https://doi.org/10.1002/hyp.14350 Coordinates of the implementation location: Pallas atmosphere-ecosystem super site, 67°59'50.2"N 24°12'33.8"E

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Characterizing managed aquifer recharge systems with state-of-the-art tritium and noble gas measurement techniques and integrated surface-subsurface hydrological modelling

Research Project  | 3 Project Members

The broad focus of this research project is the improvement of the conceptual and quantitative understanding of surface water-groundwater interactions via state-of-the-art tritium measurement techniques and integrated surface-subsurface hydrological modelling. The specific goal is the development of a dissolved gases and water stable and tritium isotopes based method for the continuous monitoring of managed aquifer recharge (MAR) systems, which are considered the most important mitigation measures against the negative impacts of climate change on water availability. The field site is Switzerland's largest managed aquifer recharge (MAR) site Hardwald in Muttenz, Basel. Continuous analysis of the spatial and temporal distribution of tritium in the river Rhine and in the groundwater wellfield is achieved with the deployment of portable mass spectrometers for dissolved gas analyses and automated sampling devices for the sampling for water for isotopic analyses. In addition, within the framework of the project a new state-of-the-art tritium enrichment line is being built within Eawag's environmental tracer laboratory. The new enrichment line is combining recent methodological developments of IAEA's isotope hydrology laboratory and of Eawag's environmental isotope tracer group. The measurement of low-level tritium concentrations will thus be made possible via an improved electrolytic enrichment method for tritium in small volume water samples, followed by low level liquid scintillation counting. The efficient measurement system for natural to ultra low level tritium concentrations, the online monitoring of dissolved gases and the integrated modelling method will provide a new toolbox for the near real-time quantification of the flow and mixing of different groundwater sources in MAR systems. The numerical modelling is based on a high resolution 3-D geological model incorporated into an integrated surface-subsurface hydrological model (ISSHM). The modelling software HydroGeoSphere, the inverse modelling software PEST++ and the data assimilation software PDAF will be used for model construction, model calibration and real time modelling.

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Resilient water management in tectonically active, intensely used watersheds - Combining online tracer & seismic monitoring with integrated hydrological modelling of climate change & water use

Research Project  | 8 Project Members

Out of all our natural resources, water underpins sustainable development by far the most, and is thus critical in achieving the Sustainable Development Goals (SDG) defined by the United Nations in 2015. While water is the focus of only 1 of the 17 SDG, guaranteeing safe and sustainable drinking water resources to future societies is elementary for achieving every single SDG. Groundwater (GW) - the most elusive component of the water cycle - comprises more than 30% of the word's freshwater resources. While often overlooked or dramatically over-simplified in hydrological analyses, a robust assessment of the temporal and spatial distribution of GW quantity, quality and renewal rates was identified as a key factor in designing resilient and sustainable water resources management plans for future societies. One of the hydrologic systems most in need of improved methods for the development of integrated water management plans are tectonically active, volcanic watersheds, particularly volcanic island states, as volcanic systems represent an important and highly valuable source of clean water, owing to their typically large subsurface permeability & porosity (i.e., outstanding filtering capacity) and good water quality. The water cycle of the volcanic island nation Japan (JP) with its over 100 active volcanos, for example, is deeply linked to the volcanic activity of the Pacific Ring of Fire. The tendency of volcanic systems to form complex networks of faults, fissures, and clinkers makes Japan's watersheds some of the most complex on Earth, with groundwater-surface water (GW-SW) interactions being even more dynamic than elsewhere and GW flow paths extremely difficult to identify and characterize. To design resilient and sustainable water resources management plans of volcanic watersheds for future societies, a robust conceptual understanding and accurate quantification of GW recharge rates, flow paths, and SW-GW interactions are indispensable. However, most of the widely employed hydrological tracer and modelling methods are unsuitable for a robust assessment of GW circulation, renewal rates, and GW-SW interactions in volcanic systems, and conceptual gaps in understanding volcanic GW circulation exist. Considering the accelerated anthropogenic and climate-induced changes to our environment, international crises and increasing water use conflicts, an interdisciplinary understanding of volcanic GW systems is more important than ever before. To overcome these impediments and provide guidance for the design of resilient sustainable integrated water resources management plans for future societies, new hydrological tracer and modelling methods that can be used to detect and quantify deep GW circulation in tectonically active, volcanic watersheds must be developed. In this research project, we thus develop a framework for the integrated assessment of water resources in volcanic regions, building on technologies that only recently became accessible for watershed-scale hydrological studies: Integrated surface-subsurface hydrological modelling, high-resolution 3-D models of complex geological systems, continuous on-site monitoring of dissolved gases and microbes in water, and high resolution local/regional projections of climate change until the end of the 21 st century. The watershed of Mt. Fuji, JP, where deep GW was found to flow up along the tectonically most active fault system of JP and enrich shallow GW and springs based on the aforementioned tracers, will serve as experimental site. Continuous monitoring stations of deep and shallow GW and spring sites will be setup, combining novel gas-equilibrium membrane-inlet portable mass spectrometry and online flow cytometry technologies. The continuous tracer analyses will be complemented with a large body of additional tracer analyses and hydraulic observations, serve to detect the influence of seismicity on deep GW circulation, and be used for calibration of an integrated SW-GW flow model of Fuji watershed. Climate change and water use projections will then be used for predictive modelling with the calibrated model, and based thereon, resilient and sustainable water resources management strategies designed.