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

Sammanfattning

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.