A Study on Groundwater Levels Following Rewetting of Drained Wetlands in Southern Sweden

Sammanfattning

In light of recent hot and dry summers, restoration of degraded wetlands has been considered as an opportunity for increasing water availability in the landscape. Despite the lack of evidence-based outcomes of rewetting on hydrological functions, the Swedish government continues to allocate funds for further implementation. This study addresses this gap by investigating responses in high temporal resolution groundwater levels (GWL) to rewetting of two historically drained wetlands within Östergötland County, southern Sweden. To assess hydrological alterations, a Before-After-Control-Impact approach was employed, using a drained but non-rewetted wetland as the control. The aim of the study was to investigate GWL changes following rewetting, both within the peatlands and in adjacent areas, and identify factors determining these responses. The results showed spatial variation of rewetting effects, both within and across sites. While one of the rewetted wetlands showed increased and stabilized GWL, providing reasons to think that restoration improved hydrological functions, the other exhibited limited responses. To improve restoration outcomes, this study emphasizes the importance of considering both local conditions for planning, implementing and monitoring rewetting efforts, along with data quality assurance as an essential step prior to further application. Recognizing that the results of restoration were not consistent in this study may not be a limitation of rewetting itself, but rather a reflection of the sometime irreversible changes that historical intensive drainage has imposed on these ecosystems.