Hydrogeology (Schilling)

Im Sommer trocknen verschiedene kleine und mittlere Fliessgewässer im Kanton Basel-Landschaft aus. Als Folge des Klimawandels ist zu erwarten, dass Trockenperioden länger und häufiger auftreten und sich die Auswirkungen von Wasserentnahmen noch verschärfen. So konnten entlang der Ergolz bereits beobachtet werden, dass auch die Grundwasserentnahme für die Wasserversorgung den Abfluss von Oberflächenwasser beeinflussen können.

Fliessgewässer stehen in Wechselwirkung mit dem Grundwasser, so existieren entlang von Wasserläufen Bereiche, in denen Flusswasser in den Grundwasserleiter infiltriert, und solche, in denen Grundwasser in das Oberflächengewässer exfiltriert. Vor allem wenn im Sommer mehr Grundwasser entnommen wird, und der Grundwasserspiegel sinkt, kann sich dies auf den Abfluss in den Wasserläufen auswirken. So schreibt das Wasserschutzrecht vor, dass dem Grundwasser nicht mehr Wasser entnommen werden darf, als ihm natürlicherweise zufliesst. Es darf auch nicht so viel Wasser aus einem Grundwasserleiter entnommen werden, dass der Wasserlauf beeinträchtigt wird.

Um diese Auswirkungen abzumildern, sind geeignete betriebliche Massnahmen oder auch Massnahmen zur Wasserrückhaltung erforderlich. So könnten z.B. ein ausgeglichenes Pumpenregime im Laufe des Tages in geringeren Absenkungen des Grundwassers resultieren. Möglich ist auch das Festlegen von Grundwasserständen unterhalb derer im Falle einer Trockenperiode kein Wasser mehr entnommen werden darf. Ein solcher Schwellenwert kann z.B. dem Grundwasserstand entsprechen, der erforderlich ist, um eine gewünschte Wassermenge im Fluss zu erhalten. Eine Möglichkeit, um einerseits das Grundwasserdargebot in Trockenperioden zu erhöhen und dem Trockenfallen der betroffenen Fliessgewässer entgegenzuwirken, ist die künstliche Grundwasseranreicherung der betroffenen Talgrundwasserleiter (Managed Aquifer Recharge MAR). Dabei könnte der Grundwasserspiegel durch die künstliche Infiltration von Oberflächenwasser so angehoben werden, dass dieser hydraulisch höher liegt als das Fliessgewässer, und damit Grundwasser in das Oberflächengewässer exfiltrieren kann (Managed Surface Water Recharge MSWR). Die künstliche Grundwasseranreicherung soll dabei bei Mittel- und Hochwasserabfluss (im Winter und den Übergangsjahreszeiten) stattfinden, während sommerlicher Niedrigwasserperioden könnte dann vergleichsweise «kühles» Grundwasser in die Fliessgewässer exfiltrieren. Neben einer quantitativen Optimierung, einschliesslich einer Erhöhung des Grundwasserdargebots und der Grundwasserexfiltration während Niedrigwasserperioden, würde auch eine ökologische Aufwertung von Flussabschnitten (Massnahme bzgl. Hitzestress) erzielt.

Für den Pilotstandort im Bereich der Wüeri östlich von Sissach wurde ein Oberflächen- und Grundwasserbeobachtungssysteme aufgebaut (insgesamt 9 Grundwassermessstellen und 3 Pegelmessungen in den Oberflächengewässern Ergolz und Homburgerbach). Gegenwärtig wird ein Grundwasser- und Wärmetransportmodell aufgebaut und parametrisiert. Anschliessend werden nach einer Kalibrierung sowie Validierung des Modells für den Pilotstandort Modellszenarien und Feldversuche formuliert. Mittels Modellszenarien sollen die oben aufgeführten hydraulischen Bedingungen (kontinuierlicher Betrieb und hydraulische Schwellenwerte) als auch MAR-MSWR-Konzepte untersucht werden. Gegenwärtig werden auch in Zusammenarbeit mit der Scherrer AG Abflussmessungen in der Ergolz bei Niedrigwasser vorgenommen, welche eine weitere Validierung der Modelle erlauben.

The ICDP-funded Bushveld Drilling Project (BVDP) aims to generate a continuous vertical stratigraphic sequence of the mineral and resources-rich Bushveld Igneous Complex (BIC) in South Africa. Within this framework, a specific focus is directed towards gathering water-related data, aimed at enhancing the understanding of deep groundwater systems in relation to water and energy security. The present project complements the already ongoing and funded collaborative activities between the Hydrogeology group of UniBas, the main partner's group at University of the Free State, and the BVDP, via the addition of state-of-the-art measurements of radio-noble gases dissolved in water. The determination of the radio-noble gas isotope concentrations of ³⁹Ar, ³⁷Ar, ⁸⁵Kr, and ⁸¹Kr, alongside the already planned analyses of classic environmental tracers [i.e., stable water isotopes (∂¹⁸O, ∂²H), atmospheric noble gas concentrations (He, Ar, Kr, Xe), and other ratio isotopes (³H,³He, and ⁴He)] will allow the characterization (i) of the residence times and flow dynamics of the suspected hundreds-of-thousands- to millions-of-years old deep groundwater, which in turn enables the assessment of the spatial extents and hydraulic properties of the different lithological units in the BIC, (ii) of the origins of suspected large amounts of dissolved CH₄, which in turn enables assessment of the potential for using CH₄ from the BIC for sustainable energy production, and (iii) enable estimating the quantity, quality, and vulnerability of groundwater and therefore the suitability for using it as a drinking water source.

Im Auftrag der Flughafen Zürich AG und in Zusammenarbeit mit der Geo Explorers AG führt die AUG durchflusszytometrische Messungen für einen Testbrunnen am Flughafen Zürich durch. Im Rahmen des Projekts «Geothermische Energie für den Flughafen Zürich» und der Untersuchung des Untergrunds für geothermische Speicheranwendungen wird kontinuierlich mit unserem Online-Durchflusszytometer BactoSense gemessen. Ziel ist es, die Mikrobiologie des Tiefengrundwassers und ihren Zusammenhang mit der Grundwassernutzung zu erforschen.

80% of Switzerland's drinking water is originating from groundwater. Climate change-induced droughts and increased demand for irrigation put groundwater under considerable pressure and cause widespread concern. In 2021, two popular initiatives were launched to protect groundwater and 2 parliamentary motions concerning groundwater were accepted in 2022/23. Now, for more than 3000 wells capture zones have to be delineated until 2035, and 4000km of rivers have to be restored within the next 70 years. Groundwater modelling plays an important role in tackling these challenges. However, the robustness of the current modelling practice is undermined by the poor characterisation of the subsurface, the computational challenges to jointly simulate surface- and groundwater and by the large resulting uncertainties. Consequently, stakeholders have to deal with complex issues but cannot fully exploit the potential of modelling to help them make relevant decisions.

In this project, we are addressing these shortcomings by (1) Employing cutting-edge mass-spectrometry technology to expand the available tracer methods with non-toxic gas tracers injected into the subsurface. This will greatly expand the spatial and temporal scales of available tracer methods and open new pathways to subsurface characterisation. (2) Building on the latest generation of integrated surface-subsurface hydrological models (ISSHM). This will allow joint consideration of the surface, the subsurface, and the operational infrastructure. Through the direct simulation of tracers, the model calibration is also far more robust and unique. (3) Providing the technological and computational means for real-time data assimilation in ISSHMs. This will guarantee that the model is always close to the real system state and thus can be continuously used to support operational decision-making. We have demonstrated the technical feasibility of all of these developments in our previous work.

This BRIDGE Discover project allows us to move this fundamental research to an operational level by collaborating among the three institutions through 12 coordinated work packages. In close collaboration with the relevant stakeholders, we develop and assess the efficiency of our hydrogeological service for two pilot studies: one to increase the efficiency of irrigation for agriculture, and the second one to predict the influence of a renaturation on well capture zones.

InnoGeoPot - Innovative exploration methods for geothermal potential assessment and energy storage

With the steady increase in the number of installed geothermal energy systems (GES) in Europe, a more frequent use of thermal energy in geological layers of different depth has been recognized.

In particular, the use of shallow and medium-depth geothermal potential can be extended to the application of systems for borehole thermal energy storage (BTES), as well as the possibility of rehabilitating abandoned deep boreholes with closed-loop borehole heat exchangers (BHE).

The development of multi-scale geological-hydrogeological-thermal models in combination with decision support systems (DSS) provide a better understanding of geothermal potential through the application of different GES.

Content and aim of the research project

The research work will aim to develop geological-hydrogeological-thermal models at different scales using data collected from deep boreholes in selected areas and to monitor real operation data from geothermal wells to determine heat rejection/extraction rates.

The research area includes the wider area of the city of Zagreb in Croatia, the city of Ljubljana in Slovenia and the cross-border area between north-eastern Slovenia and south-eastern Croatia.

In the selected urban and rural pilot areas, the exploration of geothermal potential at shallow and medium-depth between 200 and 500 m is being explored through the application of BHE for BTES. The geothermal potential from the rehabilitation of abandoned boreholes is also being evaluated.

Scientific and social context of the research project

The trilateral research cooperation between Croatia, Switzerland and Slovenia will lead to the establishment of an international research group dealing with the characterization of the subsurface and technology development in the field of geothermal energy.

For the selected pilot areas, an up-to-date DSS for the use of shallow and medium-depth geothermal energy will provide a valuable tool to ensure a more efficient and sustainable use of geothermal energy.

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 together with municipalities and farmers in a co-creative process, and their impacts on increased water availability and decreased streamflow extremes assessed. The Slow Water project consortium consists of the Hydrogeology and the Global and Regional Land-Use Change groups of University of Basel, the regional authorities of the Cantons of Basel-Landschaft and Luzern, municipalities, farming associations and the private sector.

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.

The effects of climate change on Swiss water bodies, including the impact on river temperatures and discharge, can already be observed today. As part of the research project "Future river temperatures in Switzerland under climate change - SwissFuRiTe", nationwide projections of future river temperatures were simulated for all 82 river monitoring stations of the Federal Office for the Environment (FOEN).

For this purpose, we chose a novel modeling approach that combines air temperatures from 22 general circulation and regional climate models (GCM-RCM) and runoff projections from 4 hydrological models as input for 2 semi-empirical surface temperature models. With these models, future projections of river water temperatures could be simulated for the 3 climate emission scenarios (RCP2.6, RCP4.6 & RCP8.5).

The river monitoring stations were grouped and the results analyzed according to thermal regimes (lake, Central Plateau/Jura, Alpine, regulated and springs), which are influenced by different thermal processes upstream.

The surface temperature models air2stream (rivers) and air2water (lakes) were used to determine which of the two models is better suited to the settings of the respective river monitoring stations. While air2stream was used at all sites, the air2water model was used at sites where the influence of lake water upstream dominated the temperature signal in the rivers.

The study showed that the most important factor for the level of temperature increase by the end of the 21st century is the climate emission scenarios. For the RCP2.6 scenario, the mean change in river water temperature from the reference period (1990 to 2019) to the near (2030 to 2059) and distant future (2070 to 2099) is 0.8 and 0.9 °C respectively. The largest temperature increase can be observed for the RCP8.5 scenario, in which the mean river water temperature rises by 1.2 and 3.1 °C for all stations in the near and distant future. The rate of warming differs for each station depending on the upstream processes. In addition, the seasonal trends in air temperature and discharge amplify the warming of watercourses in summer as a result of higher air temperatures and lower discharge volumes. While the increase in runoff and the lower warming of the atmosphere in winter also lead to a lower warming of the watercourses.

An analysis of thermal threshold and extreme values shows that heatwaves in Switzerland are likely to increase in the future. On the basis of our study, we were able to identify particularly vulnerable river sections, both those that are already at risk today and those that will be at risk in the future.

Future studies should focus on counteracting the local negative effects of climate change. The results of our study can be used to identify river sections with increased vulnerability and to designate targeted refugia for aquatic organisms.