In this project we develop new and efficient tracer methods for managed aquifer recharge systems. Tracer methods that we develop encompass natural tracer signals such as tritium, stable water isotopes, dissolved (noble) gases and microbes measured at high temporal resolution and at a precision that allows tracking even small tracer signals. The new tools are suitable for MAR systems based on infiltration basins/channels as well as for induced riverbank filtration.
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authors => protected'van Rooyen, J.; Vennemann, T.; Purtschert, R.; Affolter Kast, A.; Brennwald, M. S.; Kipfer, R.; Schilling, O.&nb sp;S.' (157 chars)
title => protected'Anthropogenic tritium as a continental-scale tracer in river-derived recharg e' (77 chars)
journal => protected'Nature Water' (12 chars)
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description => protected'Groundwater, enhanced through managed aquifer recharge (MAR), plays a centra l role in mitigating current and future water stress. Here we evaluate anthr opogenic and natural water isotopes as tracers of groundwater flow dynamics within alluvial MAR systems. High-resolution sampling (daily/weekly) of stab le isotopes (δ<sup>18</sup>O and δ<sup>2</sup>H) and tritium (<sup>3</sup> H), influenced by nuclear power plant effluents, is used to trace and quanti fy the movement of infiltrated river water through an alluvial aquifer along the Rhine River in Switzerland. Time-series deconvolution is applied to qua ntify the tracer-based travel time distribution and to predict travel times throughout the entire MAR scheme. The results demonstrate the suitability of <sup>3</sup>H as a quasi-conservative travel time tracer in systems where t he infiltrating river water is marked by nuclear power plant discharges—a situation prevalent along the banks of many large river basins globally. Deu terium excess proved equally effective as a bulk travel time tracer, reflect ing distinct seasonal meltwater signals expected in major European rivers. T hese findings quantify MAR recovery rates and wellhead protection zones, sup porting sustainable groundwater management under natural and anthropogenic p ressures.' (1301 chars)
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authors => protected'Peel, M.; Solanki, K.; Brunner, P.; Hunkeler, D.; Schill ing, O. S.; Kipfer, R.' (113 chars)
title => protected'A controlled and scalable noble gas injection method for quantitative tracer tests in hydrogeological studies' (109 chars)
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categories => protected'noble gases; artificial tracers; drinking water; quantitative tracer tests' (74 chars)
description => protected'Dissolved noble gases have been recognized for decades as ideal artificial h ydro(geo)logical tracers, as they are chemically inert, invisible, and non-t oxic. However, their widespread adoption has historically been limited by th e difficulty of tracer injection, sampling, and analysis procedures. Develop ments in portable, high-resolution dissolved gas measurement technology over the last two decades have rekindled interest in the use of gas tracer metho ds for routine hydrogeological investigations, such as well-to-well tracer t ests, intra-well tests, or studies of river infiltration towards alluvial aq uifers. The application of gases in aqueous environments still poses unique challenges compared to other tracer methods, as potential exsolution and deg assing need to be accounted for, and, if possible, avoided during tracer inj ection. Here, we present a simple and efficient methodology that addresses t hese challenges and allows the efficient, on-site preparation and injection of highly concentrated tracer solutions with controlled dissolved gas concen trations. We applied the method in a large drinking water wellfield and perf ormed well-to-well tracer tests in an unconfined aquifer using helium-4 (<su p>4</sup>He), neon-20 (<sup>20</sup>Ne) and krypton-84 (<sup>84</sup>Kr). Kn own tracer quantities were injected together with fluorescent dyes into an o bservation well upgradient of a pumping well. Gas tracer breakthrough was mo nitored in the pumping well with a portable mass spectrometer. Breakthrough curves of <sup>4</sup>He and <sup>84</sup>Kr compared favorably with fluores cent dye tracers, and enabled reliable estimates of groundwater flow velocit ies, travel times, and tracer recovery. These findings illustrate how noble gases can substitute or complement other artificial tracer methods, even in large-scale settings. The methodology can be extended to other gases (e.g., neon-22, xenon isotopes, light hydrocarbons), significantly expanding the ra nge of artificial tracer...' (2055 chars)
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authors => protected'Currle, F.; Therrien, R.; Schilling, O. S.' (62 chars)
title => protected'Explicit simulation of microbial transport with a dual-permeability, two-sit e kinetic deposition formulation using the integrated surface–subsurface h ydrological model HydroGeoSphere' (184 chars)
journal => protected'Hydrology and Earth System Sciences' (35 chars)
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description => protected'Assessing the transport behaviour of microbes in surface water–groundwater systems is important to prevent contamination of drinking-water resources b y pathogens. While wellhead protection area (WHPA) delineation is predominan tly based on dye injection tests and advective transport modelling, size exc lusion of colloid-sized microbes from the smaller and usually less conductiv e pore spaces causes a faster breakthrough and thus faster apparent transpor t of microbes compared to that of solutes. To provide a tool for better asse ssment of the differences between solute and microbial transport in surface water–groundwater systems, here, we present the implementation of a dual-p ermeability, two-site kinetic deposition formulation for microbial transport in the integrated surface–subsurface hydrological model HydroGeoSphere (H GS). The implementation considers attachment, detachment, and inactivation o f microbes in both permeability regions and allows for multispecies transpor t. The dual-permeability, two-site kinetic deposition implementation in HGS was verified against an analytical solution for dual-permeability colloid tr ansport. The suitability of the model for microbial transport in integrated surface–subsurface hydrological settings at the wellfield or small headwat er catchment scale is demonstrated by two illustrative examples. The first e xample is a benchmark for integrated rainfall–runoff and streamflow genera tion modelling to which we added microbial transport from a conceptual manur e application, demonstrating the novelty of explicit and coupled microbial a nd solute transport simulations in an integrated surface–subsurface hydrol ogical scenario. The second example is a multi-tracer flow and transport stu dy of an idealized alluvial riverbank filtration site, in which we simulate in parallel the transport of reactive microbes, conservative <sup>4</sup>He, and reactive <sup>222</sup>Rn, demonstrating the assessment of mixing ratio s, tracer breakthrough c...' (2589 chars)
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authors => protected'Jannis, E.; Love, R. V.; Annette, A.; Stefan, S.; S chilling, O. S.' (101 chars)
title => protected'Climate change adaptation and mitigation measures for alluvial aquifers - so lution approaches based on the thermal exploitation of managed aquifer (MAR) and surface water recharge (MSWR)' (186 chars)
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categories => protected'managed aquifer recharge MAR; managed surface water recharge MSWR; thermal g roundwater exploitation; renewable energy; climate change adaptation' (144 chars)
description => protected'As climate change adaptation strategies, both Managed Aquifer (MAR) and Surf ace Water Recharge (MSWR) are not only highly suitable tools to mitigate neg ative effects on water resources but also bear large potential for concomita nt exploitation of thermal energy. They should thus form an integral part of any sustainable water resources management strategy. However, while at glob al scale general water resource adaptation and mitigation measures are discu ssed widely, measures that build on thermal exploitation of MAR and MSWR, an d which are readily adaptable to various different local and regional scale conditions, have yet to be developed.<br />Here, based on systematic numeric al analyses of the sensitivity of groundwater and surface water recharge as well as water temperatures to climate change, we present adaptable implement ation strategies of MAR and MSWR with concomitant exploitation of their ther mal energy potential. Strategies and feasibility benchmarks for the exploita tion of hydrologic and energetic potentials of MAR and MSWR were developed b ased on three hydrologically and hydrogeologically contrasting urban study s ites near the city of Basel, Switzerland. Our studies show projected trends in the number of days when surface water temperatures exceed 25 °C examined for various streamflow and climate scenarios.<br />We illustrate that local hydrogeologic settings and hydrological boundary conditions as well as lega l aspects affect to which degree MAR and MSWR are suitable solutions as clim ate change adaptation measures. Optimal situations for exploiting the potent ial of seasonal heat storage in MAR and MSWR exist where subsurface travel t imes between the injection and the withdrawal or exfiltration point are betw een 4 and 8 months and legal limits allow a sufficiently large temperature s pread. In such settings, the exploitable water flux and temperature spread o f MAR and MSWR reaches a heat potential of 14 to 20 MW (i.e., corresponding to 3 to 7 wind power pla...' (2394 chars)
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Anthropogenic tritium as a continental-scale tracer in river-derived recharge
Groundwater, enhanced through managed aquifer recharge (MAR), plays a central role in mitigating current and future water stress. Here we evaluate anthropogenic and natural water isotopes as tracers of groundwater flow dynamics within alluvial MAR systems. High-resolution sampling (daily/weekly) of stable isotopes (δ18O and δ2H) and tritium (3H), influenced by nuclear power plant effluents, is used to trace and quantify the movement of infiltrated river water through an alluvial aquifer along the Rhine River in Switzerland. Time-series deconvolution is applied to quantify the tracer-based travel time distribution and to predict travel times throughout the entire MAR scheme. The results demonstrate the suitability of 3H as a quasi-conservative travel time tracer in systems where the infiltrating river water is marked by nuclear power plant discharges—a situation prevalent along the banks of many large river basins globally. Deuterium excess proved equally effective as a bulk travel time tracer, reflecting distinct seasonal meltwater signals expected in major European rivers. These findings quantify MAR recovery rates and wellhead protection zones, supporting sustainable groundwater management under natural and anthropogenic pressures.
van Rooyen, J.; Vennemann, T.; Purtschert, R.; Affolter Kast, A.; Brennwald, M. S.; Kipfer, R.; Schilling, O. S. (2026) Anthropogenic tritium as a continental-scale tracer in river-derived recharge, Nature Water, 4, 444-454, doi:10.1038/s44221-026-00616-x, Institutional Repository
A controlled and scalable noble gas injection method for quantitative tracer tests in hydrogeological studies
Dissolved noble gases have been recognized for decades as ideal artificial hydro(geo)logical tracers, as they are chemically inert, invisible, and non-toxic. However, their widespread adoption has historically been limited by the difficulty of tracer injection, sampling, and analysis procedures. Developments in portable, high-resolution dissolved gas measurement technology over the last two decades have rekindled interest in the use of gas tracer methods for routine hydrogeological investigations, such as well-to-well tracer tests, intra-well tests, or studies of river infiltration towards alluvial aquifers. The application of gases in aqueous environments still poses unique challenges compared to other tracer methods, as potential exsolution and degassing need to be accounted for, and, if possible, avoided during tracer injection. Here, we present a simple and efficient methodology that addresses these challenges and allows the efficient, on-site preparation and injection of highly concentrated tracer solutions with controlled dissolved gas concentrations. We applied the method in a large drinking water wellfield and performed well-to-well tracer tests in an unconfined aquifer using helium-4 (4He), neon-20 (20Ne) and krypton-84 (84Kr). Known tracer quantities were injected together with fluorescent dyes into an observation well upgradient of a pumping well. Gas tracer breakthrough was monitored in the pumping well with a portable mass spectrometer. Breakthrough curves of 4He and 84Kr compared favorably with fluorescent dye tracers, and enabled reliable estimates of groundwater flow velocities, travel times, and tracer recovery. These findings illustrate how noble gases can substitute or complement other artificial tracer methods, even in large-scale settings. The methodology can be extended to other gases (e.g., neon-22, xenon isotopes, light hydrocarbons), significantly expanding the range of artificial tracers available for routine hydrogeological investigations.
Peel, M.; Solanki, K.; Brunner, P.; Hunkeler, D.; Schilling, O. S.; Kipfer, R. (2026) A controlled and scalable noble gas injection method for quantitative tracer tests in hydrogeological studies, Water Research, 294, 125505 (10 pp.), doi:10.1016/j.watres.2026.125505, Institutional Repository
Explicit simulation of microbial transport with a dual-permeability, two-site kinetic deposition formulation using the integrated surface–subsurface hydrological model HydroGeoSphere
Assessing the transport behaviour of microbes in surface water–groundwater systems is important to prevent contamination of drinking-water resources by pathogens. While wellhead protection area (WHPA) delineation is predominantly based on dye injection tests and advective transport modelling, size exclusion of colloid-sized microbes from the smaller and usually less conductive pore spaces causes a faster breakthrough and thus faster apparent transport of microbes compared to that of solutes. To provide a tool for better assessment of the differences between solute and microbial transport in surface water–groundwater systems, here, we present the implementation of a dual-permeability, two-site kinetic deposition formulation for microbial transport in the integrated surface–subsurface hydrological model HydroGeoSphere (HGS). The implementation considers attachment, detachment, and inactivation of microbes in both permeability regions and allows for multispecies transport. The dual-permeability, two-site kinetic deposition implementation in HGS was verified against an analytical solution for dual-permeability colloid transport. The suitability of the model for microbial transport in integrated surface–subsurface hydrological settings at the wellfield or small headwater catchment scale is demonstrated by two illustrative examples. The first example is a benchmark for integrated rainfall–runoff and streamflow generation modelling to which we added microbial transport from a conceptual manure application, demonstrating the novelty of explicit and coupled microbial and solute transport simulations in an integrated surface–subsurface hydrological scenario. The second example is a multi-tracer flow and transport study of an idealized alluvial riverbank filtration site, in which we simulate in parallel the transport of reactive microbes, conservative 4He, and reactive 222Rn, demonstrating the assessment of mixing ratios, tracer breakthrough curves, and travel times in an integrated manner via multiple approaches. The developed simulation tool represents the first integrated surface–subsurface hydrological simulator for reactive solute and microbial transport and marks an important advancement to unlock and quantify governing microbial transport processes in coupled surface water–groundwater settings. It enables meaningful WHPA delineation and risk assessments of riverbank filtration sites with respect to microbial contamination even under situations of extreme hydrological and microbial stress, such as flood events.
Currle, F.; Therrien, R.; Schilling, O. 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, doi:10.5194/hess-29-5383-2025, Institutional Repository
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)
As climate change adaptation strategies, both Managed Aquifer (MAR) and Surface Water Recharge (MSWR) are not only highly suitable tools to mitigate negative effects on water resources but also bear large potential for concomitant exploitation of thermal energy. They should thus form an integral part of any sustainable water resources management strategy. However, while at global scale general water resource adaptation and mitigation measures are discussed widely, measures that build on thermal exploitation of MAR and MSWR, and which are readily adaptable to various different local and regional scale conditions, have yet to be developed. Here, based on systematic numerical analyses of the sensitivity of groundwater and surface water recharge as well as water temperatures to climate change, we present adaptable implementation strategies of MAR and MSWR with concomitant exploitation of their thermal energy potential. Strategies and feasibility benchmarks for the exploitation of hydrologic and energetic potentials of MAR and MSWR were developed based on three hydrologically and hydrogeologically contrasting urban study sites near the city of Basel, Switzerland. Our studies show projected trends in the number of days when surface water temperatures exceed 25 °C examined for various streamflow and climate scenarios. We illustrate that local hydrogeologic settings and hydrological boundary conditions as well as legal aspects affect to which degree MAR and MSWR are suitable solutions as climate change adaptation measures. Optimal situations for exploiting the potential of seasonal heat storage in MAR and MSWR exist where subsurface travel times between the injection and the withdrawal or exfiltration point are between 4 and 8 months and legal limits allow a sufficiently large temperature spread. In such settings, the exploitable water flux and temperature spread of MAR and MSWR reaches a heat potential of 14 to 20 MW (i.e., corresponding to 3 to 7 wind power plants), and energetic exploitation becomes a suitable tool either for local low-temperature heat applications such as heating and hot water or for ecological use as a heat and water buffer in rivers affected by seasonal droughts. As a positive side effect, climate-induced warming of groundwater resources and temperature increases in drinking water withdrawals would be mitigated simultaneously.
Jannis, E.; Love, R. V.; Annette, A.; Stefan, S.; Schilling, O. 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 (11 pp.), doi:10.1016/j.watres.2023.119988, Institutional Repository
