The Model of Land Surface Movements Induced by Groundwater Rebound in the Area of Former Mining Exploitation

<p>The objective of the research was to investigate the process of rock mass recompaction related to groundwater rebound induced by underground mining. Research has been conducted in the area of the closed copper ore mine (Konrad) as well as the anhydrite and gypsum mine (Lubichów) in south-eastern Poland.</p><p>The mining operation was carried out in the years 1944-2001 in the area of the Konrad mine and 1944-2015 in the area of the Lubichów mine. It resulted in substantial land subsidence of up to 1.4 m and drainage of the aquifer system. However, it is estimated that the subsidence caused by groundwater pumping during these periods was 0.3 m in total. Furthermore, the spatial extent of the depression cone in the aquifer system immediately after the cessation of exploitation significantly exceeded the limits of the mining areas. Following the closure of the mine, a continuous increase in the groundwater head and land uplift is observed.</p><p>Classical survey results and the Persistent Scatter Satellite Radar Interferometry (PSInSAR) method were used to determine land surface movements in the period from November 2015 to November 2020. The results of the research show in the area of the Lubichów mine closed in June 2015, vertical land uplift reached a maximum of approx. 92 mm in that period. At the same time, in the Konrad mine area, closed in March 2001, no significant land uplift was observed. However, the main part of the investigation concerned the development of a novel method of land uplifting prediction. As a result, an attempt was made to comparatively analyze the dynamics of land uplift associated with the life cycle of the mine and the increase in the groundwater head.</p><p>These analyzes allowed the time factor for the modelling of the land uplift to be determined. This time factor is approx. 5 months in the area of the Lubichów mine and indicates that there is a time lag between the start of the groundwater head increase and the land uplift occurrence. Also, the investigation revealed that land uplift will occur in the analyzed area for the next five years. However, the dynamics of such movements will gradually decline in the years to come.</p><p>The methodology developed could be applied to any post-mining area where groundwater rebound-related uplifts are observed. It may be an appropriate tool for estimating both the time during which the land uplift is expected to begin after the mine drainage has been stopped, as well as the total duration of the land uplift phenomena.</p>

Investigation of present-day ground displacement in Taiyuan basin by InSAR in the context of interbasin water transfer project

<p>Located in the middle of Shanxi Province, northern China, Taiyuan basin is a dry and water-short region. This region is reaching alarming levels of aquifer depletion due to decades of groundwater overexploitation, which has caused severe land subsidence in the basin. The Wanjiazhai Water Diversion Project (WWDP) was designed to ease water scarcity by transporting water from the Yellow River to the Taiyuan basin through 452.4 km-long canals. By the end of 2018, the WWDP had supplied 2.87 billion m<sup>3</sup> of water to Shanxi Province, which replenish the basin’s surface water body as well as the underground aquifer. The groundwater levels have continued to rise since 2003, with rising levels of more than 70 meters by 2018 in comparison with its low stand in 2000.</p><p>In this study, we use 2007-2010 ENVISAT, ALOS-1 data, and 2017-2020 Sentinel-1 data to study the response of the basin’s aquifer to the groundwater rebound against the background of the water transfer project. We addressed the issue of tropospheric delay and its impact on the seasonal deformation by combing GACOS (Generic Atmospheric Correction Online Service) and a common-point stacking method. The accuracy improvement of deformation by this correction method was validated with measurements from seven continuous GPS stations in the basin. Groundwater rebound triggers ground uplift, which was identified in five areas by InSAR with a rate up to 25 mm/yr. The uplifting displacement time series are well correlated with groundwater level recovery. The land subsidence in the south of the basin continues but the rates decreased significantly in 2017-2020 detected from Sentinel-1 as compared to that in period 2007-2010 from ENVISAT and ALOS-1. All these uplifting signals and the decreasing rates of land subsidence found in Taiyuan city provide the indication that water management practices are successful in mitigating further subsidence.</p><p>We found a significant seasonal displacement concentrated within the central region of the basin corresponding to the main irrigated areas in the Taiyuan basin. The maximum peak-to-peak amplitude is 43 mm observed from ENVISAT and decreases to 20 mm observed from Sentinel-1. The seasonal amplitudes change rapidly across faults, indicating that the fault is an effective barrier to across-fault fluid flow. To further quantify the causal relationships between water level and ground displacement, groundwater levels and ground displacement at three wells located near the area affected by significant seasonal land subsidence are analyzed by Cross Wavelet Transform (XWT) method. We found the time lags of about one month between land subsidence and the forcing groundwater level declines. Such a cross wavelet analysis with high spatial-temporal resolution therefore enables tracking the health of the aquifer system and highlights the system’s sustainability in aiding water resources allocation against the background of the water diversion project.</p>

Satellite-Based Monitoring and Modeling of Ground Movements Caused by Water Rebound

The presented research aimed to evaluate the spatio-temporal distribution of ground movements caused by groundwater head changes induced by mining. The research was carried out in the area of one of the copper ore and anhydrite mines in Poland. To determine ground movements, classical surveying results and the persistent scatter Satellite Radar Interferometry (PSInSAR) method were applied. The mining operation triggered significant subsidence, reaching 1.4 m in the years 1944–2015. However, subsidence caused by groundwater pumping was about 0.3 m. After mine closure, an ongoing groundwater rebound was observed. Hence, land uplift occurred, reaching no more than 29 mm/y. The main part of the investigation concerned developing a novel method for uplift prediction. Therefore, an attempt was made to comparatively analyze the dynamics of ground movements correlated with the mine life and hydrogeological condition. These analyses allowed the time factor for the modeling of land uplift to be determined. The investigation also revealed that in the next six years, the uplift will reach up to 12 mm/y. The developed methodology could be applied in any post-mining area where groundwater-rebound-related uplift is observed.

Land deformation associated with exploitation of groundwater in Changzhou City measured by COSMO-SkyMed and Sentinel-1A SAR data

The Urban Agglomeration in Yangtze River Delta is one of the most important economic and industrial regions in China. The City of Changzhou is one of the most important industrial citys in Yangtze River Delta Urban Agglomeration. Activities here include groundwater exploration. Groundwater overexploitation has contributed to the major land deformation in this city. The severity and magnitude of land deformation over time were investigated in Changzhou City. A Small Baseline Subset Interferometric Synthetic Aperture Radar (SBAS-InSAR) technology, provides a useful tool in measuring urban land deformation. In this study, a time series of COSMO-SkyMed and Sentinel-1A SAR images covering Changzhou City were acquired. SBAS-InSAR imaging technique was used to survey the extent and severity of land deformation associated with the exploitation of groundwater in Changzhou City. Leveling data was used to validate the SBAR-InSAR productions, the error of SBAR-InSAR annual subsidence results was within 2 mm. The results showed that three main land subsidence zones were detected at Xinbei, Tianning and Wujin District. Four subsidence points were selected to analyze the temporal and spatial evolution characteristics of land subsidence. The subsidence rate of P1 to P4 was −2.48 mm/year, −12.78 mm/year, −18.09 mm/year, and −12.69 mm/year respectively. Land subsidence over Changzhou showed a trend of slowing down from 2011 to 2017, especially in Wujin District. SBAR-InSAR derived land deformation that correlates with the water level change in six groundwater stations. Indicated that with groundwater rebound, the land rebound obviously, and the maximum rebound vale reached 9.13 mm.