Satellites Watch China’s Sinking Ground Slowly Rise Back as Aquifers Recover

Beneath the plains of northern China, the ground is quietly changing direction. In the Xiong’an New Area, a rapidly urbanizing region about 100 kilometers southwest of Beijing, decades of intensive groundwater pumping pressed the land surface steadily downward, threatening infrastructure, buildings, and the region’s ambitious urban plans. Now, as groundwater levels begin to recover, a team of Chinese researchers has documented something remarkable: the sinking has slowed dramatically, and across broad swaths of the area, the land has begun a tentative, delayed rebound. The study, published in Earth Science Informatics, combines satellite radar measurements, wavelet-based time-series analysis, and numerical modeling to trace how the ground deforms as aquifers recover from overexploitation, offering one of the most detailed accounts yet of subsidence reversal in a major alluvial plain.

The research team, led by Dekang Pan and Wenping Mu of the China University of Geosciences in Beijing, focused on a challenge that matters far beyond one city. Land subsidence driven by groundwater extraction is a global hazard, affecting megacities from Mexico City to Jakarta to Tehran. A widely cited 2021 assessment in Science mapped the global extent of the threat and found that subsidence endures across vast populated areas where aquifers are being drawn down faster than they recharge. What has been far less certain is what happens when the trend is reversed, as is now occurring in parts of the North China Plain thanks to aggressive groundwater regulation and the massive South-to-North Water Diversion Project, which has shifted surface water northward and eased pressure on underground reserves.

To capture the ground’s movements with millimeter-scale precision, the researchers turned to a satellite technique known as Small Baseline Subset Interferometric Synthetic Aperture Radar, or SBAS-InSAR. The method works by comparing radar echoes from a constellation of satellite acquisitions over time, stacking many small-baseline interferograms so that subtle shifts in the phase of the returned signal reveal vertical ground motion. Unlike single interferogram approaches, SBAS-InSAR suppresses atmospheric noise and decorrelation errors by relying on many overlapping pairs of images, producing a coherent time series of deformation at thousands of measurement points across the landscape. The resulting maps track not just how fast the ground is moving, but where and when those movements accelerate, decelerate, or reverse.

The satellite record revealed a strikingly heterogeneous picture. Rather than subsiding uniformly, the region splits into distinct deformation zones: two areas of relatively pronounced subsidence, one area showing only a weak tendency to sink, and a broad mixed-deformation area that displays an overall weak rebound tendency. This spatial patchwork reflects the underlying geology. The Xiong’an New Area sits on thick Quaternary sediments laid down over millions of years, in which layers of water-bearing sand and gravel aquifers alternate with low-permeability clay-rich aquitards. How much any patch of ground sinks or rises depends on the thickness, compressibility, and connectivity of those layers, which vary considerably across the plain.

To interpret the temporal structure of the deformation, the team applied multiscale wavelet analysis, a mathematical tool that decomposes time series into components of different frequencies without losing information about when each component occurs. Wavelet methods are particularly well suited to hydrogeological problems because groundwater systems respond to forcing at multiple timescales, from seasonal pumping cycles to multi-year recovery trends, and because responses to changes in water level are often delayed. By examining how the deformation signal aligns with groundwater-level records across different scales, the researchers identified apparent lag effects between rising water levels and the ground’s response, a hallmark of water slowly draining into or out of compressible clay layers.

Those lags carry deep physical meaning. The researchers interpret the deformation during groundwater recovery within a conceptual framework involving three coupled processes: immediate elastic rebound of the pumped aquifers, delayed rebound at the boundaries of intervening aquitards, and delayed compression of the middle portions of thick aquitards. When pumping stops and water levels rise, sandy aquifer layers, which are stiff and highly permeable, expand almost instantly, like a compressed spring released. But clay-rich aquitards behave differently. Water moves through them very slowly, so excess pore pressure dissipates at their boundaries first while their interiors may continue consolidating for years. This means some parts of the subsurface can be rebounding even as other parts continue to compact, and the net surface motion is the sum of these competing signals.

Crucially, the study suggests that the length of the apparent deformation lag is controlled not only by aquitard thickness, the factor most commonly emphasized in classical consolidation theory, but also by the stratigraphic configuration of the entire aquifer-aquitard system. The order, continuity, and hydraulic connection of layers determine where drainage water enters and exits the clays and therefore how quickly internal pore pressures equilibrate. This insight has practical consequences: two locations with equally thick aquitards can exhibit different rebound behavior if their stratigraphic architecture differs, meaning that subsidence forecasts built on thickness alone may misjudge how fast the land will stabilize.

Looking forward, the team ran numerical simulations of coupled groundwater flow and aquifer-system compaction under an average-year, business-as-usual reference scenario, assuming continued mean hydroclimatic conditions and current groundwater-use patterns. The model results point to a continued reduction in the actively subsiding area, with a progressive transition from rapid subsidence to slow subsidence and, eventually, to slow rebound. In other words, even without further policy intervention, the system appears to be moving in the right direction, though the recovery is gradual and unevenly distributed across the deformation zones identified in the satellite data. Subsidence rates overall are decreasing, while the rebound rate in the mixed-deformation area is increasing, a trend consistent with progressive pore-pressure recovery through the layered sequence.

The findings carry weight for urban planning in Xiong’an itself, which has been designated as a model city of more than five million people and is being built largely from scratch. Subsidence poses direct threats to tunnels, pipelines, high-speed rail alignments, and flood defenses, and a national-scale 2024 assessment published in Science documented measurable subsidence in dozens of China’s major cities. Demonstrating that careful groundwater management, reinforced by inter-basin water transfer, can bend the deformation curve offers a template for other overexploited basins. Comparable reversals have been documented in Tianjin and in the Beijing Plain following water diversion and pumping restrictions, suggesting that the North China Plain is emerging as a natural laboratory for aquifer recovery.

Methodologically, the study also makes the case for integration. Satellite-derived deformation time series provide the spatial detail that well networks cannot; wavelet analysis extracts multiscale timing relationships that reveal hidden lags; and process-based numerical models translate those observations into predictions under future scenarios. Each tool alone would leave critical questions unanswered. Together, they show that the ground beneath Xiong’an is not simply sinking or rising, but breathing in a slow, layered rhythm dictated by the interplay of water pressure, clay compressibility, and time. As aquifers continue to refill across the North China Plain, monitoring that rhythm will be essential to ensuring that one of the world’s largest urban construction projects rests on ground that is, at last, slowly steadying itself.

Subject of Research: Land subsidence and rebound induced by groundwater-level recovery in the Xiong'an New Area, North China Plain

Article Title: Spatiotemporal evolution of land subsidence and rebound induced by groundwater-level recovery: A case study from the North China plain

Article References: Pan, D., Mu, W., Guan, F., Yan, A., Wu, X., Xu, N., & Zhang, X. (2026). Spatiotemporal evolution of land subsidence and rebound induced by groundwater-level recovery: A case study from the North China plain. Earth Science Informatics, 19(11), Article 189. https://doi.org/10.1007/s12145-026-02241-4

Image Credits: AI Generated

DOI: 10.1007/s12145-026-02241-4

Keywords: land subsidence, groundwater recovery, North China Plain, Xiong'an New Area, SBAS-InSAR, wavelet analysis, aquifer-system compaction, aquitard delay, numerical modeling, groundwater overexploitation, land rebound, remote sensing