Ground motion and water
Punjab ground motion, 2016–2024
Satellite radar can measure ground motion of millimetres per year. Over Punjab, eight years of Sentinel-1 data show where the land is sinking, and a model then asks how much of that may come from groundwater.
What the radar measures
Three viewing tracks
One ascending and two descending Sentinel-1 tracks see the ground from different sides.
From phase to motion
Repeat images are compared through interferometry, unwrapped and corrected for the atmosphere with ERA5.
Vertical and east motion
Where the two directions overlap, line-of-sight motion is split into vertical and east components at 90 m, assuming no north motion.
Click any point
The maps show monthly time series relative to the reference area and the first month, averaged on a grid of about 0.9 km.
From sinking ground to groundwater
The inversion explorer splits observed vertical motion into groundwater storage, permanent compaction and surface load. In its default layer, Model D's groundwater storage has a median of −32.7 mm of water per year, on a scale of ±80.
Read the comparison with care. W3RA contains no irrigation pumping, GLDAS-2.2 assimilates GRACE so it is not independent, GRACE cells are about 300 km wide, and the wells' depths are unknown. Coherence is also low over cropland: in one study box the share of reliable pixels was 0.80 in built-up land against 0.05 on cropland, so measurements there lean on towns and villages.
Explore the maps
Deformation explorer
Vertical, east and line-of-sight velocity with clickable monthly series, October 2016 to January 2024.
Open map →Deformation: full period
The same maps over the longest window, January 2016 to May 2024.
Open map →Inversion explorer
Groundwater storage, compaction and load, compared with hydrological models, GRACE and wells.
Open map →Data quality explorer
Coherence, unwrapping connectivity and velocity per track, with adjustable quality masks.
Open map →The maps are hosted on GitHub Pages and open in a new tab. Processed from Copernicus Sentinel-1 data. Basemap © OpenStreetMap contributors.
Explore your own data
The HydroInSAR Web Viewer is an open-source tool in the same spirit. It opens NetCDF, HDF5 and MintPy time-series cubes, with demo InSAR and W3RA data, so you can click grid cells and fit curves to their histories.