Towards Monitoring Groundwater Table Depth in Peatlands from Sentinel-1 Radar Data

Groundwater table depths (WTD) control peat formation and greenhouse gas emissions from peatlands. Therefore, monitoring WTD is of great interest for restoration and climate change mitigation actions. In shallow groundwater systems such as peatlands, moisture in the topsoil is influenced by and often in hydrostatic equilibrium with WTD. Sentinel-1 provides C-band radar data with high temporal and spatial resolution. Since backscattered microwave radiation is sensitive to the soils' dielectric permittivity of the first centimeters, radar data provides a promising tool to obtain spatial information not only on soil moisture but also on WTD. We evaluate the correlation between time series of backscatter coefficients σ0 and WTD measured in situ at > 50 dip wells using a change detection approach. Study area is the Dromling peatland in Germany. Overall, we observe an increase in σ0 with shallower WTD. For a few sites and time periods σ0 also decreased during wettest conditions and related partial inundation. Preliminary results from the Dromling peatland show that temporal correlation coefficients vary strongly among sites and reach on average 0.57. Time series indicate that the σ0- WTD dependency partly disappears during summer.