Geophysical and Hydrogeological Characterization of a Drained Peatland – Investigating Pre-Restoration Conditions at Plönninge Testbed

Abstract

Peatlands provide several ecosystem services such as carbon sequestration and improved water quality and availability. However, historical drainage has led to a massive loss of peatlands worldwide, resulting in lost ecosystem functions and increased greenhouse gas emissions. Today, environmental goals have led to a renewed interest in the restoration of peatlands. However, knowledge gaps regarding site-specific parameters for restoration success remain. To address these knowledge gaps, this study employs the geophysical methods Ground Penetrating Radar (GPR) and Direct Current Induced Polarisation (DCIP) to characterize the geological and hydrogeological conditions of a formerly drained peatland located in Plönninge in the south of Sweden. The geophysical measurements were combined with data from borehole logs, water quality measurements and monitoring of groundwater levels to create four conceptual models of the subsurface. An investigation of the site’s history was also conducted. GPR measurements provided resolution to a depth of 3 m, and showed the border between peat and underlying layer. DCIP provided data to a depth of 30 m, although resolution decreased with depth, and displayed a shallow layer of cohesive material, as well as bedrock. The geophysical data was cross-referenced using borehole logs and groundwater level monitoring. The study demonstrated that current groundwater levels in the peatland are not optimal for peat function. The resulting models demonstrate the effectiveness of geophysical methods to map peatlands. The models will be used in an ongoing study about the effect of rewetting a drained peatland.

Abstract (Swedish)

Våtmarker bidrar med många ekosystemtjänster såsom kolinlagring och förbättrad vattenkvalitet och tillgänglighet. Historisk dränering har dock lett till en massiv förlust av våtmarker världen över, vilket resulterat i förlorade ekosystemfunktioner och ökade utsläpp av växthusgaser. Idag finns ett ökat intresse för återställning av våtmarker för att nå beslutade klimat- och miljömål. Det finns dock fortfarande kunskapsluckor gällande vilka platsspecifika parametrar som avgör resultatet av en restaurering. För att fylla i dessa luckor har vi i denna studie använt de geofysiska metoderna markradar (GPR) och likströmsinducerad polarisation (DCIP) för att få en bättre förståelse för de geologiska och hydrogeologiska egenskaperna i en dikad torvmark belägen i Plönninge i södra Sverige. Data från de geofysiska mätningarna kombinerades med data från borrhålsloggar, vattenkvalitetsmätningar och mätningar av grundvattennivån för att skapa fyra konceptuella modeller över marken. En kartläggning av platsens historia gjordes också. GPR-mätningarna nådde ett djup på 3 meter och visade tydligt gränsen mellan torv och underliggande lager. DCIP-mätningarna nådde ett djup på 30 meter, upplösningen minskade dock snabbt med djupet, och från dem kunde ett ytligt lager av kohesionsmaterial och berggrund kartläggas. De geofysiska mätningarna utvärderades med hjälp av borrhålsloggarna och datan från grundvattennivå-mätningarna. Studien visade att nuvarande grundvattennivåer är för låga för optimal torvfunktion. Resultatet visade att geofysiska mätningar är en effektiv metod att kartlägga torvmarker på. Modellerna kommer att användas i en pågående studie om återvätningen av en dränerad torvmark.

Popular Abstract

Creating a Geological Model of a Drained Peatland

Peatland restoration may help combat several environmental problems, such as carbon dioxide emission, flood risk and loss of biodiversity. However, more research is needed to find out which drained peatlands can be successfully restored and which are best left alone. We used non-invasive underground imaging techniques known as geophysical methods to gain knowledge about a drained peatland in the south of Sweden that is about to be restored. By studying the peatland both before and after restoration, we will have gained more knowledge about the local conditions needed for restoration success.

By rewetting peatlands, carbon sources can be turned to carbon sinks and a natural biotope with potential to increase biodiversity and lower flood risk is restored. Sounds too good to be true? Maybe it is! Not all restored peatlands magically turn back to their pristine conditions, and sometimes they start by releasing more greenhouse gasses than before! That is why more research is needed to find out what makes some peatland restorations more successful than others.

To combat this knowledge gap, a new research project on a historically drained peatland in Plönninge in the south of Sweden was started in 2024. As a part of this project, we used the geophysical methods GPR and DCIP to investigate the geology of the area. GPR stands for Ground Penetrating Radar, and uses the time it takes for electromagnetic waves to travel in the ground and back to the surface to visualize the underground. DCIP stands for Direct Current Induced Polarization, and uses a strong electrical current to measure the ground’s ability to conduct and store electricity. Together with measured groundwater levels and drillings, we created a model of the area that describes the geology and groundwater conditions before restoration.

The model showed that there is a shallow layer of clay and silt in the area. Because water runs incredibly slow in clay, this layer divides the groundwater in the area into two water-bearing units. The clay layer also creates a shallow groundwater table, which historically created the wet conditions needed for peat to form. However, there were several signs of drainage and peat decomposition, created by the constructed ditches in the area. By filling in the ditches, the peatland could potentially return to its pristine form.

The project also showed that GPR and DCIP were useful tools when investigating peatlands. The DCIP could depict the ground down to a 30 m depth, showing the bedrock and the clay layer, while the GPR depicted the first three meters and clearly showed the depth of the peat.

So, how will this help in separating the bad apples (peatlands) from the good when we are deciding on which peatlands to restore? Unfortunately, one study is not enough to confidently decide the geological conditions that contribute to restoration success. But when we know the restoration outcome for the peatland in Plönninge, one more jigsaw piece is added to the puzzle, increasing our common knowledge of peatlands and restoration and hopefully helping in future decision-making.

The research in Plönninge continues, which gives us the exciting opportunity to closely follow all the changes in biodiversity, water quality and geophysics that could happen during the process of restoration. We would also suggest a further deep-dive into the groundwater flow in the area (not literally), as well as the measurement of changes in the emissions of greenhouse gases. Stay tuned!

• author: Blake, Elsa and Lewin, Signe
• supervisor: Tina Martin; Clemens Klante
• organization: Civil Engineering (M.Sc.Eng.); Division of Engineering Geology
• alternative title: Geofysisk och hydrogeologisk karakterisering av en utdikad torvmark – förstudie inför återvätning av Plönninge testbädd
• course: VTGM05 20261
• year: 2026
• type: H3 - Professional qualifications (4 Years - )
• subject: Earth and Environmental Sciences
• keywords: Geophysics, Peatland, Conceptual model, GPR, DCIP
• other publication id: ISRN LUTVDG(TVTG-5200)/1-40/(2026)
• language: English
• additional info: Examiner: Jan-Erik Rosberg
• id: 9243979
• date added to LUP: 2026-06-29 11:53:35
• date last changed: 2026-06-29 11:53:35