MSc Thesis ideas’ catalogue 2023

Water Resources Research Group

With contributions from GEUS, Geo, IGN – Skov Natur og Biomasse, and Luxembourg Institute of Science and Technology (LIST), and links to many more national and international partners.

Overview of MSc Thesis ideas contained in this catalogue

1. Hydrogeologisk model for Storkøbenhavn
2. Power to X and water balance in shallow aquifer
3. Hydrological modelling of future groundwater resources in Ghana
4. Hydrology, greenhouse gases and biodiversity in an untouched forest (urørt naturskov)
5. Does global warming give us an opportunity of using water isotopes to derive the infiltration year of groundwater?
6. The future Copenhagen: Saltwater intrusion or flooding?
7. Spatial and seasonal patterns of vadose zone hydrology in a forest landscape
8. Hydrology and geochemistry of a drained and rewetted forest peatlands in Gribskov
9. Hydrological modeling for sustainable groundwater management in South Africa
10. Hydrological and hydrogeological investigations of Ayad catchment in India
11. Hydrological modelling in realtime and forecast mode for hydrological planning and warning systems
12. Power-to-X: win-win solution to groundwater flooding?
13. Collaboration with international research institute in Jülich
14. Application of satellite remote sensing data in hydrological models
15. Climate change effects, mitigation and adaptation
16. Simulation of tracer transport at the scale of a groundwater protection zone using a numerical flow model
17. Effects of re-wetting lowlands on catchment hydrology
18. Detailed modeling of wetland hydrology to reduce greenhouse gas emissions
19. Tracing intrusion and freshening from groundwater chemistry patterns in coastal aquifers
20. The oxidation of Fe 2+ by oxygen in the presence of different iron oxides
21. Hydrological modelling of nutrient-poor peatlands: Bøllemosen case study
22. Developing Enhanced Weathering for Carbon Capture and Storage
23. Protecting the groundwater resource - assessment of pesticide leaching at the field scale
24. Machine learning to predict pesticide leaching
25. Estimating groundwater-surface water exchange with two different modeling approaches
26. Using nitrate as a tracer to infer transport times – to assess the vulnerability of the groundwater
27. Using tracers to quantify the degree of preferential leaching in connection with rainfall events
28. Maintaining sustainable groundwater use under changing climate (1)
29. Maintaining sustainable groundwater use under changing climate (2)
30. Effect of subsurface heterogeneity on reactive transport
31. Your project?

1. Hydrogeologisk model for Storkøbenhavn

Geo har en meget detaljeret geologisk model (hydrostratigrafiske model) for Storkøbenhavn i 25×25 meter grid, som løbende bliver opdateret efterhånden, som ny viden kommer til fra f.eks. anlægsprojekter og vandressourceopgaver. Modellen kan ses in GeoAtlasLive og den geologiske modellering foregår løbende i GeoScene3D.

Hovedformålet er at udbygge den hydrostratigrafiske model til en hydrogeologisk model via en række delopgaver og derefter anvende modellen til en konkret opgave.

Delopgaverne er:

• at forbedre den hydrostratigrafiske model for de prækvartære lag ved hjælp af logstratigrafiske inddeling af kalken. Datagrundlaget skal baseres på geofysiske logs fra Gerda Databasen, samt indsamling af Geo’s mange geofysiske logs og flowlogs (Findes i Geo’s databaser, samt en del på vores projekt drev). Datagrundet øges herved betydeligt.
• at udarbejde transmissivitetskort for kalken og evt. for sandmagasiner i Storkøbenhavn baseret på data og tolkninger af data fra Jupiter Databasen (autotolkning af Q/s data, ntilbagepejlingsdata og udtræk af de ”få” transmissiviteter, som ligger direkte i Jupiter) samt samle data fra Geo’s mange pumpforsøg. Efter dataindsamling udføres geostatistik analyse af data og der optegnes et eller flere bud på transmissivitetskort, som senere kan indgår i den hydrologiske model.
• at lave kort med fordeling af hydraulisk ledningsevner for de forskellige hydrostratigrafiske delinger i kalken baseret på borehulslogs, flowlogs og under hensyntagen til andre processer såsom glaciale påvirkninger og strukturelle forhold (forkastninger, foldninger etc.)
• at opstille, kalibrere og anvende den eksisterende hydrologisk model (MIKE SHE) ved at inddrage resultaterne fra de forrige delopgaver. Modellen kan enten opstilles i MIKE SHE eller (GMS) MODFLOW og der skal være særlig fokus på grundvandsforholdene i kalken.

Det aftales nærmere hvilke(n) delopgave(r), som der skal lægges mest vægt på baseret på den studerendes ønsker. Der er også muligt at selv være med til at samle data ind i felten.

Formål

• Dataindsamling fra forskellig kilder og kvaliteter
• Logstratigrafiske analyse
• Geostatistik analyse
• Geologisk modellering GeoScene3D
• Numerisk modellering i MIKE SHE eller MODFLOW

Contact persons:

Flemming D. Christensen (Geo, fdc@geo.dk), Mia Haahr Saxtoft (Geo, mhs@geo.dk)
og Jesper Lind (Geo, jel@geo.dk), og Søren Jessen (sj@ign.ku.dk)

2. Power to X and water balance in shallow aquifer

In an area close to the town of Lemvig a Power to X plant (PtX) has been planned. For the planned PtX process there is a significant need for clean, sufficient and stable water supply. At the same time Lemvig is facing climate challenges due to raising groundwater levels combined with critical low topographical level placement and close to Limfjord.

If active drainage/abstraction from the upper aquifer in order to lower the groundwater level to no risk level can be combined with the PtX as main consumer, the project will not only have a useful (financial) outcome for the PtX company, but also for the entire area.

Objectives:

• The objective of the project is to update the hydrogeological understanding in the upper aquifer in the area and setup a water balance model in the model code MIKE SHE.
• The most challenges areas with high groundwater levels closed to the PtX plant must be identified with the local partner – The local Utility Lemvig Vand. The required volume for the PtX Company is already identified by Lemvig Vand and must be included in to the water balance model.
• The groundwater model has to be used to present possible consequences on water levels with or without abstraction from the upper aquifer by some model scenarios including sensitive analyses on the most relevant parameters.
• The objective can be extended to include water quality by identify the PtX requirement with relevant water analysis of the upper groundwater aquifer.
• The learnings from this project can be transformed to other PtX projects and Denmark and abroad.
• The study will be carried out in collaboration with Lemvig Water Company and Klimatorium. Geo will be supervisor for Lemvig Water and will ensure the work can be directly implemented and used by Lemvig Water.

Contact persons:

Jesper Lind (Geo, jel@geo.dk), Pernille Weiland Pedersen (Klimatorium Lemvig, pewe@klimatorium.dk), or Søren Jessen (sj@ign.ku.dk).

3. Hydrological modelling of future groundwater resources in Ghana

The stress on water resources in Ghana is increasing. Due to increasing demand, population growth, pollution and the need for supply security, more attention is focusing on the groundwater reservoir as a stable and viable resource to secure a safe water supply. The project CREAM (Building Climate Resilience in Water Resources Management) is a joint project between researchers from Ghana and GEUS. The project works on setting up reliable hydrological datasets, through fieldwork and remote sensing, and setting up hydrological and groundwater models, to evaluate the surface water and groundwater resource around the capital of Ghana. The project uses projections of climate model data and future estimation of land use change to evaluate future scenarios and water resources. Depending on the timing the project could contain a trip to Ghana (nothing promised). A MSc project connected to the CREAM project could e.g., contain some of the elements below or combinations of these:

Ideas/content:

• Using different remote sensing products in hydrological modelling
• Setting up and calibrating multiple hydrological models of Densu and/or Pra and investigating performance/projections
• Setting up and calibrating a groundwater model of Densu and/or Pra
• Investigating future scenarios, e.g., future climate, abstraction and/or land use change
• Machine learning and satellite products for land use change predictions

Contact persons:

Ida Seidenfaden (GEUS, ika@geus.dk), Simon Stisen (GEUS, sst@geus.dk), and Søren Jessen (sj@ign.ku.dk)

4. Hydrology, greenhouse gases and biodiversity in an untouched forest (urørt naturskov)

Only few sites in Denmark exist where nature has been/are left untouched by human disturbance and natural biodiversity is intact. However, large areas of farmed and industrial land are now being transformed to open fields and unmanaged forest to return to natural conditions. The effects on hydrology and reversely the hydrology’s impact on this change is unknown. In the project Water4Nature we investigate the linkages between biodiversity, greenhouse gas emissions and hydrology for one of the few unmanaged, natural forest in Denmark, Draved, through a combination of field work and modelling. A MSc project can contain some of the elements below or combinations of these:

Ideas/content:

• Setup and maintenance of a hydrological monitoring network of sites in the unmanaged forest (Field work)
• Investigating of tree crown structure and density for coupling with biodiversity data, and greenhouse gas measurement field campaigns (Field work)
• Detailed hydrological modelling of the unmanaged forest including setup and calibration (Modelling)
• Detailed carbon/nitrogen modelling of the unmanaged forest (Modelling)
• Analyzing future hydrology under climate change (Modelling)

Contact persons:

Ida Seidenfaden (ika@geus.dk), Torben Sonnenborg (tso@geus.dk) and Majken Caroline Looms Zibar (mcl@ign.ku.dk).

5. Does global warming give us an opportunity of using water isotopes to derive the infiltration year of groundwater?

Groundwater is derived from rainwater. The isotope signal (the ratio between heavy and light water molecules) of rainwater is a function of the temperature in the cloud where the rain is formed. Global warming leads to an increase in the temperature, also in the clouds, implying that the increasing temperature will lead to a change in isotope signal in the groundwater.

This means that we may be able to use the water isotope signal of the groundwater to estimate when the infiltration of the water now pumped from a well took place. The isotope signal was measured for all of the GRUMO wells during 2022 (GRUMO is the national groundwater monitoring program). For some of these wells the year of infiltration has been determined using 3H/ 3 He, giving a possibility of making a direct comparison. In other places a more qualitative comparison can be made based on the depth of the groundwater, possibly supported by data from the “DK-model” of the Danish hydrological system or perhaps other models made in relation to the groundwater resource management of the water works.

A nationwide monitoring of the precipitation has slowly started, this should give us an idea of the national variation. At the moment the GRUMO samples from 2022 have been measured – but the results still need to be associated with the wells they come from (something GEUS can hopefully find resources for soon) and then of course the more interesting part is associating the isotope data with existing data from those wells of especially the groundwater age. In addition there is a partial dataset of GRUMO wells from some years ago (Sascha Müller).

Objectives:

• Objective 1.1: Analyse the literature for similar studies.
• Objective 1.2: Assist in the establishing of the national precipitation network to obtain the first impression of the national variation in the isotope composition of the precipitation.
• Objective 1.3: Make the coupling between isotope data and data from the GRUMO wells.
• Objective 1.4: Extract probable groundwater ages from the DK-model.
• Objective 1.5: Evaluate the potential of using water isotopes for age estimates of groundwater in a warming (or cooling) world.

Contact persons:

Søren Jessen (IGN) sj@ign.ku.dk, Rasmus Jakobsen (GEUS) raj@geus.dk

6. The future Copenhagen: Saltwater intrusion or flooding?

Rising global temperatures and melting of ice sheets and glaciers cause the world’s oceans to rise leading to flooding risks, saltwater intrusion, and high groundwater levels along the coastlines. In greater Copenhagen, the Frederiksberg Waterworks have been pumping drinking water for the past many decades, but they now observe increasing chloride concentrations in the drinking water, likely due to saltwater intrusion from the coast, as the drawdown cone extends close to or into the harbor. Likely this issue will be even more pressing as sea level rises in the future, potentially posing the risk of closing or reducing the drinking water abstraction from Frederiksberg.

Increasing groundwater levels are also observed in the city although groundwater abstraction keeps groundwater levels at a manageable stage, with closing or downscaling of the waterworks pumping activities, the basements in houses in the central part of the city is at risk of being flooded due to elevated groundwater levels.

These issues can be investigated with detailed hydrological modeling of the water flow and transport. The Frederiksberg Waterworks draws water from an aquifer connected to the great fault system (Carlsberg forkastningen) underneath Copenhagen. This is a complex but important flow system that is challenging to model.

As a master student, you will be connected the GeoCenter project SeaLevelRise, working on these issues. The project is a close collaboration between the GEUS department of hydrology, GEUS department of Climate and Glaciology, and Geography at IGN, KU.

Possible objectives to work with could be:

• Investigation of saltwater intrusion as a result of groundwater abstraction.
• Possible risks of groundwater flooding if abstractions are decreased or stopped.
• Simulation of the Carlsberg fault system.
• Analyzing future risk/mitigation measures for future climate change and sea level rise projections.

Contact persons:

Karsten Høgh Jensen (khi@ign.ku.dk), Ida Seidenfaden (ika@geus.dk), and Torben Sonnenborg (tso@geus.dk)

7. Spatial and seasonal patterns of vadose zone hydrology in a forest landscape

This project seeks to estimate the spatial and temporal distribution soil moisture and groundwater levels in a forested landscape in Denmark in relation to topography, forest type and climate.

The relevance of this is two-fold:

1) Groundwater formation below forests is important for our future drinking water reserve and understanding how forests interact with the soil hydrology at the ecosystem scale is important for future projections of potential groundwater formation.

2) Soil biogeochemical processes, such as greenhouse gas production and consumption, are highly dependent on soil hydrology (soil moisture content and groundwater level). Most often soil hydrology is estimated at points in the landscape and it is important to be able to interpolate the temporal variability of soil hydrology at these points to the ecosystem level.

The project will have access to a calibration and validation dataset from a mini-catchment with contrasting elevation, and concurrent measurements of soil moisture and groundwater level over two growing seasons.

Objectives:

• Investigate the links between topography, climate, forest type, groundwater and soil moisture
• Map the spatial pattern of soil moisture in a forested landscape
• Map the seasonal variation of soil moisture in a forested landscape

Contact persons:

Jesper Riis Christiansen (jrc@ign.ku.dk)

8. Hydrology and geochemistry of a drained and rewetted forest peatlands in Gribskov

Peatland hydrology is critical for the functioning of wetlands to act as atmospheric carbon sinks and flood mitigation measures. However, most peatlands in Denmark have been drained to accommodate crop or tree growth with hypothesized increased export of nutrients and faster response to precipitation events. Increasingly, the hydrology in these drained peatlands are being restored. However, it is unclear how the new hydrology relates to climatic drivers and if the export of nutrient is lowered as expected and how it develops with time after rewetting. Understanding the hydrological and geochemical response of rewetted peatlands is central for our future implementation of rewetting as a large scale tool for climate, water quality and flood mitigation in Denmark.

In this project we wish to investigate how the hydrology of drained and rewetted peatlands in Gribskov respond to climatic drivers and how the rewetting is changing the geochemistry of groundwater. The project is part of a larger Danish infrastructure project called ReWet Denmark.

Objectives

• To do field work in Gribskov by collecting water samples from piezometers and ditches in drained and rewetted peatlands.
• Analyze time series of automated groundwater level loggers in relation to climate drivers.
• Analyze water samples for geochemical composition of ditch- and groundwater.

Contact person:

Jesper Riis Christiansen (jrc@ign.ku.dk)

9. Hydrological modeling for sustainable groundwater management in South Africa

Semi-arid regions are dominated by highly irregular precipitation patterns, which strongly influence the hydrological cycle and water resources availability. Large temporal and spatial variations in precipitation causes large variability in runoff and groundwater recharge. Because of its climatic characteristics the Hout/Sand river catchment in the Limpopo province of South Africa is prone to droughts, and combined with irrigation for intensive agriculture, a growing population and climate change the region is facing severe water challenges. In order to identify sustainable groundwater management scenarios a better understanding of the hydrological processes is required, in particular the replenishment of groundwater.

Several projects can be developed in relation to an on-going Danida funded project in South Africa:

• Further development and calibration of the MIKE SHE model for the study area using both traditional data in the form of river discharge and groundwater levels and remote sensing data such as soil moisture, evapotranspiration and flooding extent. Since the rainfall-runoff relationships are complicated and partially unknown new conceptualizations need to be tested as well as alternative targets for calibration.
• Replenishment of groundwater can occur as diffuse or focused recharge. Diffuse recharge is recharge that is distributed over the catchment in response to precipitation and in semi-arid areas it often occurs as episodic events. Focused recharge occurs from rivers and managed recharge from e.g. farms and varies significantly in space and time. The two recharge components and their mutual significance at catchment scale should be analyzed using the MIKE SHE model in combination with historical data on groundwater levels as well as data currently collected from two field infrastructures established in the study area.
• Development of an alternative modelling framework for the study catchment based on MOFFLOW-6 incorporated in the GMS system.
• Analysis of impact of climate change on the hydrological components and on groundwater use and management.
• Downscaling of the hydrological model simulations to community and farm scale using machine learning techniques to help improving groundwater management at smaller scales. If relevant, the project can partly cover travel expenses to South Africa.

Contact persons:

Karsten Høgh Jensen (khj@ign.ku.dk).

10. Hydrological and hydrogeological investigations of Ayad catchment in India

Indian water resources are under strain from increasing population, intensified agricultural production, industrial development, changing food habits with growing income as well as pollution of the surface and subsurface waters. The semi-arid state of Rajasthan is particularly vulnerable. It has 10% of India’s area but only about 1% of the water resources. Although Rajasthan is mainly rural, the rate of urbanization has increased considerably over the last decades. One of the growing urban areas is Udaipur City, which now is the sixth largest city in Rajasthan and also known as the ‘city of lakes’ in India. This has led to increased pressure on the water resources and the Udaipur District is facing serious problems and challenges in securing adequate water supply of acceptable quality and in mitigating pollution of the water resources.

The water supply of the city is unique as it is largely based on water from the lakes around the city. Proper integrated water resources management in the district is hampered by insufficient knowledge of the overall water balance. The seasonal Ayad River flows through Udaipur City connecting the lakes. The seasonal and annual dynamics of this water system is poorly known and understood. To improve the understanding of the system a hydrological model analysis is required.

The activities are related to an on-going Danida funded project. If relevant, the project can partly cover travel expenses to South Africa.

Objectives:

•  Analysis of hydrological and hydrogeological data from the region.
• Development and calibration of a hydrological model for the study area.
• Use of remote sensing data such as soil moisture, evapotranspiration and flooding extent for calibration and validation.

Contact person:

Trine Enemark (tre@ign.ku.dk) and Karsten H. Jensen (khj@ign.ku.dk).

11. Hydrological modelling in realtime and forecast mode for hydrological planning and warning systems

Hydrological warning systems are gaining increasing attention in Denmark, especially after the disastrous flooding events in Germany in the summer 2021. Hydrological warning can encompass both flood and inundation warning and warning of water resources status and drought.

At GEUS, the national water resources model (DK-Model) is planned to move into both realtime and forecast mode in the coming years. This will require a rethinking of the models setup, calibration and evaluation. In addition, add-on modules for inundation of floodplains must be developed and the whole system should be placed in an operational framework linked to weather forecasts. As a master student involved in this work you can gain experience on both hydrological model development, postprocessing and visualization of data for end-users and operationalization.

A Msc project can contain some of the elements below or combinations of these.

Ideas/content:

• Modelling: Improve existing hydrological models for flood forecast or drought. Develop and test model evaluation schemes. Develop automatization schemes for 24/7 model execution and visualization. Develop inundation tools for predicting flood extend in stream valleys.
• Remote sensing: Develop algorithms for detecting free water surfaces from radar data and compare with model simulations for validation.

Contact persons:

Simon Stisen (sst@geus.dk) and Karsten Høgh Jensen (khj@ign.ku.dk).

12. Power-to-X: win-win solution to groundwater flooding?

Shallow groundwater and groundwater flooding is not only a problem for infrastructure like houses roads etc. but also is a source of excess water in urban drainage systems (sewer pipes), which significantly increase wastewater treatment costs, risks of overflow of polluted water from sewer systems to the environment, and risks of ‘backwater flooding’ from sewer systems when the capacity is exceeded. Urban areas are exposed to increased groundwater levels as a result of climate change, reduced groundwater abstraction, local infiltration of rainwater (LAR) and sealing of sewer systems. Installation of additional groundwater drainage has been suggested as a practical solution to this problem. However, simply draining the groundwater to surface water systems may not be the most feasible solution.

Here a more circular solution to the problem would be to transform excess water from being a problem to become a possible extra resource for industrial supply as part of Power-to-X electrolysis which can produce hydrogen or methane. This process requires significant quantities of water that may be extracted from shallow groundwater whereby two problems are solved simultaneously.

Objectives:

The objective of the project is to test alternative scenarios and solutions for reducing the amount of excess water in urban drainage systems caused by increased shallow groundwater levels, and instead supply such waters to the industry, where the Power-to-X technology requires significant volumes of water.

Methods:

The study will be carried out in collaboration with Lemvig water company/Klimatorium with Lemvig as case study. The Lemvig case will focus on shallow groundwater level in a strategic way, whereby inflow to the sewer systems is minimized, and a new resource is provided for industry. Figure 1 Schematic of a city where excess groundwater is used for Power-to-X.

The project will include the following tasks:

Construction of a groundwater and urban drainage water hydrological model for Lemvig municipality based on the DK model combined with a collection of urban drainage data.

Analysis of the feasibility of alternative groundwater table solutions (design of shallow groundwater drainage and/or abstraction) for reducing groundwater flow into the urban drainage system and reducing groundwater flooding and inundation problems.

Analysis of the robustness of alternative groundwater level solutions when confronted with climate change and sea level rise, and the ability to provide a stable supply of groundwater to the Power-to-X industry.

Integrated assessment of side effects on groundwater dependent terrestrial ecosystems, associated aquatic ecosystems, environmental flows, etc.

Contact persons:

Torben Sonnenborg (tso@geus.dk), Hans Jørgen Henriksen (hjh@geus.dk) and Karsten Høgh Jensen (khj@ign.ku.dk).

13. Collaboration with international research institute in Jülich

Research Center Julich in Germany is an international recognized research organization in hydrology and water resources. One of the more recent activities is the development of the Terrestrial Environmental Observatories (TERENO), an activity similar to the Danish Hydrological Observatory HOBE. The main goal of the infrastructure TERENO is to create observation platforms on the basis of an interdisciplinary and long-term aimed research program. A comprehensive array of data collection and research activities is established within the framework of TERENO and Danish students are invited to participate in the experimental and research activities through MSc thesis projects.

Funding is available for travel and living expenses.
See https://www.fz-juelich.de/en/ibg/ibg-3?expand=translations,fzjsettings,nearest-institut for more details.

Contact person:

Karsten H. Jensen (khj@ign.ku.dk)

14. Application of satellite remote sensing data in hydrological models

Satellite remote sensing data offer temporal and spatially distributed data of land surface characteristics, which can be used for driving, validating or calibrating distributed hydrological models. This study will explore the use of data from different satellite types in hydrological modeling on variable spatial scales either in Denmark or internationally. Satellite data can be utilized for deriving spatially consistent time series of relevant model input such as rainfall, potential evapotranspiration, vegetation and albedo. In addition valuable spatial pattern information can be derived from input such as land surface temperature and estimates evapotranspiration for hydrological model evaluation.

Objectives:

• Deriving hydrological relevant variables from remote sensing data.
• Testing different types of data for different problems.
• Application of remote sensing data in distributed hydrological models.
• Spatial pattern evaluation and calibration of hydrological models.

Contact person:

Karsten H. Jensen (khj@ign.ku.dk), Simon Stisen (sst@geus.dk), Julian Koch (juko@geus.dk)

15. Climate change effects, mitigation and adaptation

Many urban areas and landscapes are facing problems with flooding due to high water levels in streams and high groundwater levels in consequence of increasing precipitation. Analyses of these extreme events are required both for current and future climate conditions and solutions need to be developed to mitigate these effects. The analyses will be based on historical data, climate projections and hydrological modelling. Climate projections and hydrological modelling are subject to uncertainty, which need to be considered. The project can be focussed on urban or landscape problems either in Denmark or internationally.

Objectives:

• Hydrological modelling using either the MIKE SHE or MODFLOW-6 models based on historical data and climate projections.
• Uncertainty related to climate and hydrological modelling.
• Analysis of alternative mitigation solutions.

Contact person:

Karsten H. Jensen (khj@ign.ku.dk), Torben Sonnenborg (tso@geus.dk)

16. Simulation of tracer transport at the scale of a groundwater protection zone using a numerical flow model

Groundwater is the main drinking water source in Luxembourg, and is mostly exploited from free flowing springs draining the main aquifer of the country, the Luxembourg Sandstone. Groundwater protection zones have been defined for the recharge areas of these springs, where mitigation measures can be implemented to reduce the risk of groundwater contamination, in particular by agrochemicals leached from farmed areas. In order to relate these measures to the evolution of groundwater quality and thus judge of their effectiveness, aquifer response times estimates are essential. The aim of the thesis will be to set up a groundwater flow model for one protection zone, taking the local geological boundary conditions and land use into account and using available environmental tracer measurements for calibration, and then to calculate the transit times that can be expected from the farmed areas to the catchwork for an ideal tracer. Time allowing, reactive transport could be added to the simulations for selected agrochemicals, or different typical hydrogeological situations encountered in Luxembourg could also be modelled.

Objectives:

• Set up a numerical groundwater flow model for one Luxembourgish protection zone, integrating available geological information.
• Calibrate the numerical model using spring discharge, groundwater level and tritium measurements.
• Compute transit times from agricultural areas to the spring catchwork.
• (time allowing) Computing the effect of solute sorption on the transit times for selected compounds.
• (time allowing) Set up and calibration for other typical luxembourgish hydrogeological settings.

Contact persons:

Søren Jessen (sj@ig.ku.dk) and Julien Farlin (Luxembourg Institute of Science and
Technology – LIST, Julien.Farlin@eau.etat.lu)

17. Effects of re-wetting lowlands on catchment hydrology

Rewetting of lowlands is suggested as a way of capturing CO 2 and help achieving the national goal of reducing greenhouse gas (GHG) emission by 70% in 2030 relative to 1990. Rewetting can be achieved in many ways; cutting drains at the hillslope, let a channelized stream return to a natural meandering stream, lifting the bottom of the stream, etc. Rewetting will target specific lowlands in a catchment, but it will likely have a positive or negative effect upstream in the catchment as well. That is, we need to know what happens when we begin to change the current hydrology on the future hydrology of a catchment.

The project is affiliated to a research project called REWET, where we work with biologists from KU and SDU on the hydrology and GHG prospects. The project will advance your knowledge on development of groundwater models, their calibration, and how rewetting of lowlands can limit GHG emission.

Ideas/content:

• A sub-catchment of the headwaters of, e.g., Tryggevælde Å, will be chosen and a GeoScene3D model will be developed.
• Develop a 3D steady-state MODFLOW model including the stream package SFR2. Use of the UnStructured Grid (USG) option in MODFLOW to enhance discretization in the riparian zones.
• Calibrate a steady-state MODFLOW/SFR2 model using historic data.
• Investigate rewetting options on the hydrology of the catchment specifically groundwater-stream interactions, wet spots in the catchment, etc.
• Investigate the situation in a future wetter climate.
• Except for visits to the catchment, no field work is involved.

Contact persons:

Jacob Kidmose (jbki@geus.dk), Søren Jessen (sj@ign.ku.dk).

18. Detailed modeling of wetland hydrology to reduce greenhouse gas emissions

Rewetting of lowlands is suggested as a way of capturing CO₂ and help achieving the national goal of reducing greenhouse gas (GHG) emission by 70% in 2030 relative to 1990. Rewetting can be achieve in many ways; cutting drains at the hillslope, let a channelized stream return to a natural meanderin stream, lifting the bottom of the stream, etc. The project is affiliated to a research project called REWET, where we work with biologists from KU and SDU on the hydrology and GHG prospects. Hydrometric, hydrogeochemical, and isotopic data were collected during 2021-2022 from Elbækengen in Tryggevælde stream valley.

The main aim of the present thesis projects will be to construct a detailed HydroGeoSphere-model of the Elbækengen. Additional field work (e.g., ERT) will be conducted to close data gaps and lower uncertainty in the modelling. The overall target is to understand the hydrology of a riparian zone, geochemistry, and CO₂ uptake. The project will advance you knowledge on riparian zone hydrology and how it interacts with GHG emission. Field work experience (e.g. participation in Hydrogeological Field Course) is desirable. A driver’s license is required.

Ideas/content:

• Gather existing data and establish conceptual model/understanding.
• Development of small-scale 2D or 3D steady-state MODFLOW model to aid quantification of water fluxes and establish boundary conditions for detailed model.
• Practice HGS modeling – then advance into adding the complexity of the real field site.
• Select scenarios to test in the model.
• Supplementary field work, e.g.: Hydrogeological characterization of Elbækengen, i.e., geophysical surveys (ERT, GPR), installation of wells and slug tests, measure flow paths (seepage through streambed, overland flow, drains), sampling of water stable isotopes.
• Analysis of time series of hydrological and water stable isotope data.

Contact persons:

Jacob Kidmose (jbki@geus.dk) and Søren Jessen (sj@ign.ku.dk).

19. Tracing intrusion and freshening from groundwater chemistry patterns in coastal aquifers

The process of cation exchange in coastal aquifers gives rise to characteristic hydrochemical ‘signatures’ of the groundwater that reveal the direction of groundwater movement. For example, intrusion of Na-Cl seawater in to a fresh aquifer with a Ca-HCO₃ type groundwater results in a Ca-Cl₂ water type. And during freshening, the flushing of a saline aquifer by fresh Ca-HCO₃ water forms a Na-HCO₃ water type. These effects are typically visible when data are plotted in Piper diagrams and Stiff diagrams, which are commonly used by the industry in hydrological investigations. However, the cation exchange processes are non-linear and the salt-freshwater interface may move forth and back.

The net result is, that the hydrochemical ‘signatures’ may become blurred or masked. The aim of the proposed project is to unmask these patterns, via reactive transport modeling of cation exchange during repeated (modelled) intrusion and freshening. The results of conceptual model cases will be compared to hydrochemical data from the SaltCoast projects activities at Rømø and Brede Stream estuary/delta in south-western Denmark.

Objectives:

• Collect estuary/delta sediment and depth-matched water samples.
• Measure in the laboratory the amounts of exchangeable cations, and the cation exchange coefficients to be used in the modelling.
• Setup a 1D model to derive the hydrochemical ‘signatures’ arising from single and repeated events of intrusion and freshening.
• Develop an automated plotting scheme of the 1D-model result into e.g. Piper and Stiff diagrams. This could be done in Matlab or Python.
• Conceptualize the findings in order to broaden the applicability thereof by industry users.

Contact person:

Søren Jessen (sj@ign.ku.dk)

20. The oxidation of Fe 2+ by oxygen in the presence of different iron oxides

The iron cycle has been proposed to be one of the most important element cycles for life on Earth. Iron is an essential nutrient in itself. Further more, the precipitation or dissolution of iron oxides control the bioavailability of other nutrient (phosphorus) and control the mobility of trace elements important for water quality. Understanding the behavior of iron oxides is a therefore very important.

Objectives:

• Conduct a literature review on iron cycling in the hydrosphere.
• Follow protocols to precipitate a suite of iron oxides.
• Document their type/mineralogy by XRD, N2-BET and SEM analysis.
• Design and conduct laboratory experiments to test the kinetics of ferrous iron oxidation in the presence of oxygen and each of the prepared iron oxides.
• Model the kinetics of iron removal.

Contact person:

Søren Jessen (sj@ign.ku.dk)

21. Hydrological modelling of nutrient-poor peatlands: Bøllemosen case study

The Bøllemosen case bog, located 16 km north of Copenhagen, is encircled by forest and therefore generally nutrient poor. However, there are recent indications of deterioration of its ecological state which call for restorative actions. The bog has been previously biologically characterized, and, regarding nutrient loading, it is clear that the bog receives some nutrients by atmospheric deposition. However, little remains known about the hydrology and hydrogeochemistry of the bog, which may largely control the ecological state of the habitat. Therefore, in the proposed project, the influence of nutrient input from hydrological pathways will be addressed, in an assessment of the hydrogeology of Bøllemosen. Bøllemosen bog is one of 261 protected EU habitats in Denmark. Danish authorities therefore are responsible for  securing or improving its ecological state.

Objectives:

• Conduct a literature search to find existing (historical) hydrogeological data regarding Bøllemosen.
• Monitor a network of piezometers (existing + possibly new) and a rain gauge with respect to hydraulic head and water chemistry and stable isotopes of water.
• Conduct geophysical investigations in conjuncture with hand drillings and borehole information from existing borehole and create a conceptual hydrogeological model.
• Monitor the hydrology of surface hydrological features such as ditches, ponds, etc.
• Integrate the information with existing data to create a conceptual hydrogeological model and a water balance for Bøllemosen.
• Setup a numerical distributed hydrogeological model for Bøllemosen.

Contact persons:

Majken Zibar (mcl@ign.ku.dk) and Søren Jessen (sj@ign.ku.dk)

22. Developing Enhanced Weathering for Carbon Capture and Storage

Silicate weathering is one of the most important global sinks for atmospheric CO₂. Therefore
application of crushed silicate minerals contained in mafic and ultramafic rocks on agricultural soils
have been suggested as a method of capturing atmospheric CO₂. At the same time, the minerals will release micronutrient that may increase global food production. This method is termed Enhanced Weathering. This project investigates the effectiveness of such Enhanced Weathering, and especially the influence on the carbon capturing of geochemical reaction in the subsoil and aquifer beneath the agricultural fields. Is the atmospheric carbon really stored?

The project is based on literature, laboratory work, and geochemical modelling.

Objectives:

• Conduct a literature review on Enhanced Weathering to understand the background for the project.
• Revisit data obtained beneath soils already subjected to Enhanced Weathering to investigate the fate of uptaken atmospheric CO₂.
• Conduct laboratory work (based on existing method descriptions) to investigate geochemical
  reactions that affect the caon capture and storage efficiency of Enhanced Weathering.
• Model the transfer of atmospheric carbon to aquifers.

Contact person:

Søren Jessen (sj@ign.ku.dk)

23. Protecting the groundwater resource - assessment of pesticide leaching at the field scale

The topic of pesticide leaching and the potential risk for groundwater reservoirs is a hot topic both within Denmark and around the world. The recent years have shown numerous national stories in the media (follow link (in Danish): https://www.dr.dk/nyheder/tema/sproejtegift-i-drikkevandet) underlining the relevance of the topic. Since 1999 five field sites have been used for monitoring potential pesticide leaching in the Danish Pesticide Leaching Program (PLAP) which is still ongoing. The geochemistry department at GEUS is gathering and analyzing hydrological and geochemical data using several methods to assess the potential pesticide leaching from common agricultural applications.

Based on previous monitoring and research it is evident that the potential of pesticide leaching differs substantially depending on the geological setting. For instance, fields situated in Quaternary moraine clay deposits can be much more vulnerable compared to fields in postglacial sandy deposits. The reason for this is due to the fractures in the clay that facilitate faster transport of pesticides (follow link (in Danish): https://www.dr.dk/nyheder/indland/grafik-saadan-kan-pesticider-komme-ned-i-grundvandet). Now we also wish to assess the leaching potential at the field scale in 3D by using spatially distributed continuous monitoring data in numerical models. This could be a major step in advancing the understanding and the risk of pesticide leaching in agricultural settings.

Objectives:

• Set up a local field-scale model implementing the knowledge of the geological depositions (in GMS).
• Simulating flow and pesticide transport (in GMS).
• Optimizing the model using observation data.
• Compare the potential of pesticide leaching assessment from the 3D model to the common method in the pesticide regulatory procedure.

The main part of the thesis will consist of modeling analysis in GMS.

Contact persons:

GEUS, Sachin Karan (saka@geus.dk) and IGN, Søren Jessen (sj@ign.ku.dk).

24. Machine learning to predict pesticide leaching

Assessment of pesticide leaching to groundwater systems is critical to drinking water resources as well as surface water systems. In GEUS monitoring of pesticide have been conducted for almost 20 years. Still, estimating the leaching potential to surface-near groundwater poses great challenges. Hydrological system variables are not always well described and geological heterogeneities can be difficult to implement numerically. Therefore, based on long time series of pesticides and other variables, we want to implement machine learning to predict pesticide leaching at our test sites.

Objectives:

• To use monitoring data to train and test machine learning models to predict pesticide leaching into groundwater.
• To analyze patterns and relations between governing variables of the trained models.

Contact persons:

GEUS, Sachin Karan (saka@geus.dk) and IGN, Majken Looms (mcl@ig.ku.dk).

25. Estimating groundwater-surface water exchange with two different modeling approaches

Regional groundwater models are commonly discretized into cell sizes at the scale of 100s meters due to the large areas. Therefore, a cell size representing a stream area is also of the size of 100s meters knowing that stream widths are in the scale of 10s meters at the maximum. This means that simulated groundwater fluxes to and from the stream may not be representative as drainage areas (seepage faces) close to the stream are too small due to the large cell size occupied by the stream. Consequently, if such a model is used to assess groundwater-surface exchange (of both flow and solutes) in different scenarios related to, e.g., change in climate or land use, the predictions may be erroneous. Therefore, in this thesis project, we wish to explore the difference in exchange fluxes using different conceptualizations to represent streams in regional groundwater models. The outcome of the project will help in understanding how streams are optimally conceptualized in regional groundwater modeling and enable better simulations related to changes in climate and land use. The student should be very interested in groundwater modeling (in both Mike She and GMS) and applying GIS to handle model in- and outputs.

Objectives:

• To extract different areas of the DK-model and convert them into GMS models.
• In GMS the extracted areas will be conceptualized using regular cell sizes (that is same cell size in the entire area) and irregular cell sizes (that is irregular cell sizes with smaller cell sizes near the streams).
• Calibrate and compare the different conceptualizations in terms of parameters and simulated groundwater fluxes along streams.

Contact persons:

GEUS, Sachin Karan (saka@geus.dk), GEUS, Jacob Kidmose (jbki@geus.dk) and IGN,
Søren Jessen (sj@ig.ku.dk).

26. Using nitrate as a tracer to infer transport times – to assess the vulnerability of the groundwater

In the Danish Pesticide Leaching Program (PLAP), nitrate is monitored at all five agricultural fields together with pesticides and transformation products. While bromide has been used as a tracer to calibrate the models of the fields, the potential for nitrate as a tracer has not been explored. Therefore, we wish to perform analyses of measured nitrate concentrations to explore nitrate leaching patterns under different agricultural fields representing different geologies. Further, we wish to implement the nitrate measurements in calibrating 1D models representing the fields. By doing so, we will gain knowledge of how nitrate measurements may optimally enhance the calibration of the models and eventually predict the leaching risk of unwanted solutes to the groundwater.

Objectives:

• Analyze time series of nitrate data at different fields representing different geologies.
• Prepare nitrate data for model calibration.
• Compare results from model calibration using nitrate with results from model calibration using bromide.

Contact persons:

GEUS, Sachin Karan (saka@geus.dk), GEUS, Rasmus Jakobsen (raj@geus.dk) and
IGN, Søren Jessen (sj@ig.ku.dk).

27. Using tracers to quantify the degree of preferential leaching in connection
with rainfall events

Rapid preferential flow in bio pores and fractures is a well-known phenomenon that can have a huge impact on flow and solute transport to groundwater and surface water (follow link (in Danish): https://www.dr.dk/nyheder/indland/grafik-saadan-kan-pesticider-komme-ned-i-grundvandet). However, efficient methods to determine both size and distribution of fractures on larger scale are lacking. The geochemical department at GEUS is part of the ongoing Danish Pesticide Leaching Assessment Program (PLAP), where monitoring of hydrological and geochemical data is used to assess the risk of pesticide leaching (http://plap.dk).

In PLAP, it has been shown that fractures in clayey tills may transport pesticides much faster than what is observed in sandy soils. Therefore, the Geochemical department at GEUS wants to apply stable oxygen isotopes and analyze previously applied tracers to help quantify the preferential flow and assess the impact on transport of pesticides.

Objectives:

• Set up a sampling campaign for a catchment containing one of the PLAP fields.
• Establish additional ISCO samplers to collect stream water for stable isotope analysis.
• Data analysis of ongoing monitoring data for the PLAP field and the collected data to estimate the contribution from fracture flow in drainage, streams, and groundwater.
• (if time permits) Conceptualize the findings through numerical model analysis and test the effect on pesticide leaching.

The thesis will consist of fieldwork and monitoring in a catchment containing one of the PLAP fields.

Contact persons:

GEUS, Sachin Karan (saka@geus.dk) and Søren Jessen, (sj@ign.ku.dk)

28. Maintaining sustainable groundwater use under changing climate (1)

In Spain, the effects of climate change are indeed showing the consequences – extreme droughts are more frequent, and the groundwater reserves are stressed. Therefore, to secure the groundwater in a sustainable manner, new technologies and approaches are required. One approach is to use managed aquifer recharge (MAR), where water from various sources is infiltrated into depleting groundwater aquifers. In this thesis project, the study area is in southern Spain, where droughts and saltwater intrusion to coaster aquifers are becoming more frequent. Together with the University of Granada, Spain, we wish to explore the MAR potential to mitigate aquifer depletion using the state-of-the-art groundwater modeling code called MODFLOW 6. The code is built into the GMS software as well as python. Much of the data from the study area is already gathered and or is continuously being monitored. Still, if funding comes to place there is potential for a visit to the field site and the University of Granada.

Objectives:

• Set up a MODLFOW 6 model for the field site in Spain using the available data.
• Calibrate the model against field observations.
• Explore the capabilities of MODFLOW 6 to implement a variety of MAR processes/ structures.
• Implement climate change projections and investigate the MAR requirements to maintain a sustainable groundwater resource.

The thesis will mainly consist of modeling based on available data from the Spanish field site

Contact persons:

GEUS, Sachin Karan (saka@geus.dk) and Søren Jessen, (sj@ign.ku.dk).

29. Maintaining sustainable groundwater use under changing climate (2)

In Spain, the effects of climate change are indeed showing the consequences – extreme droughts are more frequent, and the groundwater reserves are stressed. Therefore, to secure the groundwater in a sustainable manner, new technologies and approaches are required. One approach is to use managed aquifer recharge (MAR), where water from various sources is infiltrated into depleting
groundwater aquifers. However, for MAR to be feasible, the right hydrogeological properties need to be present. In this thesis project, the study area is in southern Spain, where droughts and saltwater intrusion to coaster aquifers are becoming more frequent. Together with the University of Granada, Spain, we wish to explore the MAR potential using heat as a tracer to investigate the properties of a proposed recharge site and the underlying groundwater aquifer. We will use the state-of-the-art groundwater modeling code called MODFLOW 6. The code is built into the GMS software as well as python. Much of the data from the study area is already gathered and or is continuously being monitored. Still, if funding comes to place there is potential for a visit to the field site and the University of Granada.

Objectives:

• Set up a MODLFOW 6 model for a local field site in Spain using the available data.
• Calibrate the model against field observations.
• Explore the capabilities of MODFLOW 6 to simulate heat transport in the groundwater.
• Re-calibrate the model using temperature observations from the field site.
• Assess the field site and aquifer properties based on groundwater model analyses.
• The thesis will mainly consist of modeling based on available data from the Spanish field site.

Contact persons:

GEUS, Sachin Karan (saka@geus.dk) and Søren Jessen, (sj@ign.ku.dk).

30. Effect of subsurface heterogeneity on reactive transport

The groundwater (drinking water) resource is threatened by multiple and widely used contaminants, such as pesticides, nitrates and PFAS. The media brings daily stories on new discoveries and closure of existing waterworks. There is thus a vital need for advancing the understanding of the transport of these contaminants in groundwater at large-scale to assist the delineation of so called robust and non- robust areas on the surface, i.e., areas where a potential spill or leaching of contaminants will have a low or high impact on the groundwater quality, respectively.

Transport of solute in the groundwater is highly affected by subsurface heterogeneity related to geology and geochemistry. Small-scale ‘unsystematic’ heterogeneity will generally lead to a spreading
(dispersion) of the solutes while structural heterogeneity will alter the dominant transport pathways. Many solutes additionally behave reactively, i.e., they may undergo biological or chemical transformation or sorb to soil particles. These reactive processes may similarly exhibit spatial heterogeneity both laterally and vertically, leading to large variations in where the solutes can be found in the subsurface.

Representing the effect of subsurface heterogeneity has been a large research topic for many years, with focus on particularly small-scale heterogeneity. In the current project, focus will be mainly on the ability to represent the effect of structural heterogeneity and its impact on effective reactivity in large-scale models. The basic idea is to simulate reactive transport by fine resolution models and then setup and test different hypothesis on how these effects can be represented in coarse resolution models. The project could emphasize more on the aquifer physical properties or on the biochemical system heterogeneity, in accordance with the applicant interest.

Objectives:

Development of high-resolution numerical models. A baseline model is constructed that includes structural geological and geochemical heterogeneity. The model can be developed from scratch or based on an existing model refined to a high resolution and introducing heterogeneity inspired from high resolution geophysical data and geochemical data from the national borehole database Jupiter. From the base model, alternative models are defined with varying degree of heterogeneity. Flow and transport simulations are carried out for the developed model. The flow model may be constructed using either MIKE SHE or MODFLOW. For transport, a newly developed particle tracking code will be used (developed by Chris Henri) that is flexible in its process descriptions.

Analyses of results and development of hypothesis. Based on the model results, e.g., the degree to which the structural heterogeneity is controlling reactive transport, different hypothesis on how this can be upscaled to coarse grid models is postulated. This may include both transport processes, e.g. dispersion, and reaction processes such as sorption or transformation.

Test, analyze and refine hypotheses. The different hypotheses are tested in coarser grid models, where the structural, and small-scale heterogeneity, cannot be represented explicitly.

Contact persons:

GEUS, Anker Lajer Højberg, (alh@geus.dk) and Chris Henri, (cvh@geus.dk) and IGN, Søren Jessen (sj@ign.ku.dk)

31. Your project?

Please remember that the above MSc Thesis ideas are only ideas. You are always welcome to bring your own ideas to the table, and to discuss with us in order to develop the project that suits you best. You can also suggest to modify any of the ideas above to better suit your wishes.

Contact persons:

Majken Zibar (mcl@ign.ku.dk), Karsten Høgh Jensen (khj@ign.ku.dk), and Søren Jessen (sj@ign.ku.dk).