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Wetland Group

We are a team of interdisciplinary scientists working with freshwater wetland research. Our field of wetland research comprises ecology, hydrology, biogeochemistry and modelling. We have several large Danish, Nordic and European projects focusing on restoration of riparian wetlands, restoration of low-lying organic soils as well as development of mitigation measures to combat nutrient loads from agricultural catchments (constructed wetlands, integrated buffer zones and saturated buffer zones).

Ongoing projects


The main objective of the project is to quantify the combined effects of land use change, climate change and industrial innovation due to the green shift for catchment-scale carbon, nutrient and water cycles as well as major ecosystem services (including good ecological status of fresh waters). Read more on the project site.

  • Period: 2017-2022
  • Contacts: Brian Kronvang, Katrin Bieger and Mette V. Carstensen

Drainage mitigation measures

The overall objective of the project is to investigate the nutrient mitigation potential by new or optimised drainage mitigation measures. Specifically, two surface-flow wetlands (“mini-wetlands”) and two saturated buffer zones will be tested on their capability to remove nitrogen and phosphorus from agricultural drain water in the catchment area of Norsminde Fjord in Denmark.

  • Period: 2019-2023
  • Contacts: Dominik Zak and Carl Chr. Hoffmann


The project aims to understand how nitrous oxide (N2O) emissions from streams and the underlying processes driving them are altered by nitrogen (N) pollution and soil properties, particularly iron content and pH. Streams have been highlighted as significant, but poorly constrained sources of N2O, a greenhouse gas ∼300 times more potent than carbon dioxide. For further information, click here.

  • Period: 2021-2024
  • Contacts: Joachim Audet and Mette V. Carstensen

Recovering peatlands for global change mitigation - PhD Project

Rewetting of low-lying drained organic soils is proposed as an efficient nature-based solution to reduce greenhouse gas emissions and nutrient export from agriculture. However, we lack knowledge of the efficacy of rewetting for these ecosystem services, as different strategies have not been tested in field studies. In a multidisciplinary field experiment linking soil microbes, geochemistry, greenhouse gas emissions and hydrology, ReverCit will test a novel restoration strategy called topsoil-removal by measuring greenhouse gas and nutrient fluxes coupled to soil microbiology. Topsoil removal is expected to enhance the reduction potential, compared to increasing groundwater levels only, because the most reactive peat substrate is removed. The major outcome of ReverCit is to quantify the underlying hydrological and biological processes in rewetted soils with and without topsoil removal that will highlight benefits and limitations of this potentially more sustainable rewetting strategy.

The research in ReverCit will be conducted at a Danish “living wetland lab” in Vejrumbro, which was fully instrumented for monitoring hydrology, CO2 and CH4 fluxes and nutrients in 2022 as part of the national research infrastructure project ReWet.

  • Period: 2021-2028
  • Contact: Dominik Zak


Development of an integrated P-mitigation toolbox for bank erosion related to stream and riparian restoration projects.

  • Period: 2022
  • Contacts: Brian Kronvang


Constructed wetlands with a matrix of woodchips (i.e. bioreactors) to treat agricultural drainage water.

  • Period: 2021 – 2025
  • Contacts: Joachim Audet, Carl Chr. Hoffmann


Rewetting of low-lying organic soils. Documentation of hydrological and biogeochemical changes before and after rewetting of low-lying organic soils.

  • Period 2021 – 2025
  • Contacts: Rasmus Jes Petersen, Carl Chr. Hoffmann, Dominik Zak, Hans Estrup Andersen


EEU Horizon 2021 Zero Pollution project on how to establish safe ecological boundaries for nutrients in surface waters in the Nordic-Baltic region, including development of assessment tools for adaptation of nutrient mitigation measures in catchments.

  • Period: 2022-2025
  • Contacts: Brian Kronvang and Katrin Bieger

P-mitigation measures

Documentation of P leaching before and after rewetting. Measures to mitigate leaching of phosphorus from rewetted riparian soils and rewetted low-lying organic soils (harvesting of biomass, sand filters).

  • Period: 2020 - 2025 or longer
  • Contacts: Carl Chr. Hoffmann, Dominik Zak


The project will investigate the biological and chemical phosphorus (P) mobilisation and immobilisation processes. New field methods (litter bags, iron stripes) will be used to quantify iron reduction and concomitant P release, while lab studies will unravel the fluxes of P between pools, with particular focus on microbially mediated P precipitates. Flow path analysis and reactive transport modelling will be used to predict whether high net in-situ P release results in high P export.

  • Period: 2022-2025
  • Contact: Dominik Zak

PhosLav (P-filters)

Development and testing of P-filters to trap phosphorus in agricultural drainage water.

  • Period: 2022 – 2025
  • Contact: Carl Chr. Hoffmann

Restoring biodiversity in Danish streams

The main objective of this project is to identify how different restoration practices in Danish streams can improve biodiversity, integrating both local and catchment characteristics. For more information, click here

  • Period: 2018-2023
  • Contacts: Annette Baattrup-Pedersen, Lisbeth Henriksen


This infrastructure project aims to provide a research platform for studies on peatlands under different management practices before and after rewetting. Such a research infrastructure is needed to carefully assess the consequences of rewetting peatlands, especially for greenhouse gas balances and water quality, both of which are of critical importance for Danish policies on land use. Hence, this platform will contribute to the development of research-based guidelines for rewetting peatlands. For more information, read here.

  • Period: 2021 – 2025
  • Contacts: Hans Estrup Andersen, Rasmus Jes Petersen


An industrial PhD with the company EnviDan A/S investigating application and use of sensors for on-line monitoring of nutrients in streams, including development of machine learning methods for cleaning and calibration of big sensor data.

  • Period: 2021-2014
  • Contacts: Brian Kronvang and Sofie van’t Veen


This is the first of five projects under the Nordic Council of Ministers program on nature-based solutions. In the project, we will synthesise and present existing research on NbS relevant to the Nordic context, including relevant projects and experience, policies, knowledge gaps and cost-benefit analyses. For more information, click here.

  • Period: 2021-2022
  • Contacts: Annette Baattrup-Pedersen, Dominik Zak


The overall goal of this project is to provide practitioners, landowners, water managers and relevant authorities with a toolkit to evaluate and promote the implementation of wetlands in agricultural landscapes. This toolkit will support a holistic and multi-functional approach to climate adaptation in line with existing socio-economic and institutional contexts by optimising the delivery of hydrologically related ecosystem services (ES) with a view to maximising co-benefits whilst minimising negative consequences. For more information, read here.

  • Period: ?
  • Contact: Joachim Audet

Brian Kronvang works with research, teaching and advisory projects related to catchment science, including development of new monitoring, modelling and mitigation measures such as nature-based solutions that can be applied as targeted measures in catchments to prevent losses of sediment, nutrients and pesticides to surface waters in a period with increasing pressures from climate change.

Hans Estrup Andersen is working with monitoring, modelling and mapping of catchment processes, including hydrology and nutrient and sediment dynamics. He has a particular focus on the impact of agriculture on fresh waters.

Joachim Audet

Senior Researcher

Joachim Audet

Joachim Audet works with nutrient transformations and greenhouse gas emissions in fresh waters with a particular focus on restored wetlands in agricultural landscapes. His research focuses on the controls of greenhouse gas fluxes, especially nitrous oxide, from wetlands, rivers, lakes and on drainage mitigation measures in the context of ecosystem restoration, nutrient mitigation and climate change.

Rasmus Jes Petersen

Member of Administrative Staff

Rasmus Jes Petersen works with wetland hydrology and nutrient transformations. His main focus is on the hydrogeological architecture of wetlands, investigation of flow paths and water and nutrient balances.

Dominik Zak has 20 years’ experience in freshwater-related environmental research, land use change and restoration. He is strongly dedicated to interdisciplinary research integrating biology, ecology, microbiology and hydrochemistry across aquatic and terrestrial systems. His knowledge extends to a range of biogeochemical processes, matter fluxes and nutrient dynamics in wetlands concerning the cycles of phosphorus, nitrogen, carbon, sulphur and iron. This includes work at various spatial and temporal scales – from micro-zones in laboratory microcosms to large-scale field sampling campaigns in lakes, peatlands and river networks. The aim is to help to mitigate human impacts, conserve vital resources and decelerate detrimental anthropogenic global change more efficiently.

Ida-Emilie Fredberg Nilsson

Member of Administrative Staff

Ida-Emilie Fredberg Nilsson is cand.scient in geosciences and mainly works with the restoration of wetlands on low-lying areas. Her focus is on the hydrogeological and biogeochemical processes in her work with the ability of wetlands to retain nutrients and thus limit the discharge to surface water environments.

Carl Christian Hoffmann (Carlos) works with hydrology and biogeochemical processes in freshwater wetlands. Focus is on restoration of wetlands – both riparian wetlands and larger wetlands on low-lying organic soils. Furthermore, CCH has designed constructed surface water wetlands treating agricultural drainage water and bioreactors with a matrix of woodchips also treating agricultural drainage water.

Mette Vodder Carstensen is focusing on the transport and transformation of nitrogen between agricultural land and the receiving surface water using models and field observations. Key focuses of her research are on mitigation of nitrogen loss from agricultural land using constructed wetlands and buffer zones, along with quantification of greenhouse gas emission from fresh waters. 

Katrin Bieger is a researcher specialised in catchment modelling of hydrological processes and water quality. She has been involved in the development of SWAT+, the latest version of the Soil and Water Assessment Tool, for over eight years, focusing mostly on improving the simulation of internal catchment processes and the hydrologic connectivity of different elements of the landscape. Through various SWAT and SWAT+ applications, she has also gained substantial experience in assessing the effects of management and nutrient mitigation measures, including wetlands, in agricultural landscapes.

Ane Kjeldgaard has a long-term experience in GIS. She works especially with mapping of freshwater wetlands, surface water runoff, catchments and environmental impacts of farming.

Nichlas Hermansen

Research Fellow

Nichlas is educated in Agriculture, Nature and Environment from Aarhus University. He works with new methods to increase the potential for lower greenhouse gas emissions in connection with the restoration of wetlands. He has previously worked with modeling of nutrient turnover in Danish wetlands with a particular focus on nitrogen.

Rasmus Rumph Frederiksen

Member of Administrative Staff

Rasmus works with hydrology and nutrient dynamics. He has a particular focus on how groundwater, field drainage and wetlands affect hydrology and nutrient dynamics on a field and catchment scale.

Karolina is a PhD candidate at Aarhus University with a background in Agricultural Biotechnology. The purpose of her work is to study phosphorus biogeochemistry in managed wetlands by examining the effect of different peatland restoration techniques on the phosphorus mobility in these areas. For this scope she conducts field experiments, laboratory experiments and data analysis.