|Paper title||Nation-wide characterisation of actively subsiding basins in Iran using 7 years of Sentinel-1 InSAR time series analysis|
|Form of presentation||Poster|
Across Iran, extraction of non-renewable groundwater has sparked water-related stress, increased salinisation of groundwater sources, and accelerated ground subsidence (Olen, 2021).
Both local and regional scale land-surface deformation has resulted from the decline in groundwater levels (Motagh et al., 2008). Moreover, the gap between groundwater use and renewal is so large that the resulting short-term impacts are likely to be irreversible (Olen, 2021). Quantifying the extents and rates of deformation related to groundwater extraction could therefore inform groundwater management approaches.
Here we present a catalogue of around sixty major, currently subsiding basins within the political borders of Iran. We use the COMET LiCSAR automated processing system to process seven years (2015-2021) of Sentinel-1 SAR acquisitions. The system generates short baseline networks of interferograms. We also correct for atmospheric noise using the GACOS system (Yu et al., 2018) and perform time-series analysis using open-source LiCSBAS software (Morishita et al., 2019) to estimate the cumulative deformation.
We also present vertical and horizontal velocity components of basin subsidence obtained through the decomposition of line-of-sight InSAR velocities. Subsiding basins are characterised and catalogued using the resulting interferogram time-series based upon the extents and rates of vertical motion associated with basin and agricultural areas. LiCSBAS time series analysis reveals maximal vertical rates of subsidence reach thirty-six centimetres per year in basins north-west of Tehran.
Finally, we present and demonstrate a beta version of the COMET-LiCS Sentinel-1 InSAR Subsiding Basin Portal. The portal aims to provide tools for the online analysis of automatically processed LiCSAR Sentinel-1 interferograms and subsequent LiCSBAS timeseries. The portal’s tools are designed to allow key stakeholders to search quickly through processed imagery and make critical assessments related to the extents and rates of basin subsidence. Initially the portal characterises Iranian basins but will increasingly have a global focus. Ongoing updates will be made to the portal’s interferograms and timeseries extended as more Sentinel-1 data is acquired.
Future work will focus on determining which basins are experiencing accelerating or decelerating subsidence rates. Ultimately, our quantification of ground deformation- particularly subsidence-related to groundwater withdrawal- could contribute to the development of a wider framework for monitoring complex risk pathways in similar, water stressed regions.