Subsidence monitoring above the gas storage cavern field Epe (North Rhine-Westphalia) with Interferometric SAR displacement time series

The first Hydrogen storage caverns of Germany are planned to be constructed at the salt cavern field Epe in NRW, where 114 caverns, of which more than 50 are currently used for natural gas storage, are located. Since gas filled caverns experience convergence over time and thus cause subsidence at the surface, it is important to have a monitoring concept with high spatial and temporal resolution, to predict future subsidence and potential damage to infrastructure, but also to detect unexpected subsidence quickly and assist in identifying the cause.

Epe displays a complex surface deformation field, consisting of cavern convergence caused linear trends, as well as precipitation dependent seasonal and cavern pressure dependent contributions as shown in previous studies of the area.

As part of the SAMUH2-Project, funded by the German Federal Ministry of Economics and Climate Protection, we are working on a monitoring concept to incorporate the already established methods of yearly levelling and GNSS measurements into our approach of using Interferometric SAR (InSAR) time series, which provide not only high spatial, but also good temporal resolution. Here, we use Sentinel-1 SAR data from 2015 to 2022, and process time series by using a joint approach of persistent scatterer (PS) and distributed scatterer (DS) techniques.

Our results show good agreement of the InSAR time series with other geodetic measuring methods. We can distinguish the signals of the different source mechanisms well and can even model varying cavern convergence rates, depending on the extent of the yearly cavern depletion and filling.