Research PaperThe relationship between vegetation and groundwater levels as an indicator of spontaneous wetland restoration

•The main aim of the study was to identify areas of spontaneous wetland restoration.•The relationship between groundwater table and vegetation was investigated.•The study area was modelled using an orthogonal discretization grid.•A total of 13% of such grid cells were found to have the potential for restoration.•Good ecological effects of restoration may be achieved without any hydrotechnical engineering works.

The main aim of the research was to identify areas of spontaneous restoration by investigating the relationship between the depth to groundwater table (DTW) and vegetation. A secondary aim was to confirm whether restoration is possible without any hydrotechnical engineering. The study was performed in one of the largest wetlands in central Poland, protected as a National Park and Natura 2000 site. The study area was modelled using an orthogonal discretization grid with grid cells of Δx = Δy = 100 m. The hydrodynamic model calculations were performed with VisualMODFLOW software, which uses the finite difference method. Vegetation analysis was based on the map of vegetation compiled for the area of 17697 ha. These results were next analyzed using ArcGIS to find areas where the correlation between depth to groundwater table and vegetation units was disturbed. Areas where DTW was significantly lower than would be expected based on their vegetation were identified as areas with potential for spontaneous renaturalization: around 10% of the entire study area was indicated as such, representing 1193 such grid cells. Restoration is possible through extensification or discontinuation of agricultural use, without the need for hydrotechnical engineering works which would result in DTW changes in the study area. As the last step of the analysis, the results were validated using soil maps of study wetlands.