Long-term Groundwater Withdrawal Research Articles

Flow-geomechanics coupling constrains fault geometry in induced earthquakes

Post-mortem analysis of earthquakes induced by fluid extraction or injection is often complicated by the uncertainty in the location and geometry of the causative fault. The 2011 Lorca earthquake in southeast Spain is believed to have been triggered by long-term groundwater withdrawal, causing slip along the Alhama de Murcia Fault (AMF) dipping northwest. However, the regional InSAR deformation data can be equally fit by AMF and an unmapped fault located approximately 5-8 km west of AMF and dipping southeast, which creates an ambiguity in the causative fault that hosted the earthquake. Here, we show that the assumptions of elastic dislocation, undrained deformation, and decoupling between flow and deformation processes contributed to the ambiguity, which can be resolved by conducting a fully coupled analysis that provides additional constraints on the problem. We test that hypothesis and propose that the Lorca earthquake was likely caused by the rupture of a southeast dipping fault plane, which is antithetic to AMF. We build a mechanistic model of groundwater withdrawal over the time period of interest (1960–2010) that includes pressure diffusion, aquifer contraction, crustal unloading, and basement expansion mechanisms. The model identifies the difference in production-induced loading of the two faults: AMF experiences poroelastic compression and down-dip shear whereas the antithetic fault experiences tension and up-dip shear. We demonstrate that two-way coupling between flow and deformation processes plays a crucial role in the natural selection of the causative fault. The proposed framework holds the potential to detect hidden faults capable of hosting earthquakes.

Effect of seawater intrusion on groundwater in the Demak coastal area Indonesia: a review

One of the most complicated areas to repair on the North Shore of Central Java is the beach in the Sayung Demak. More than 300 hectares of land have been flooding in the last five years due to high tides. The erosion area in Sayung area has also been affected by port development activities in the Semarang area, thus changing the hydrodynamic nature of Sayung Demak Waters. Overuse of groundwater has been showing to lead to brine ingress in the coastal region. And long-term groundwater withdrawal forces land subsidence formation. A few waterfront structures in Sayung waters were built as breakwaters to decrease incoming waves. The solution presently used to minimize erosion while catching sediment in the Sayung area is hybrid engineering. The purpose of this study is to review the effectiveness of hybrid engineering in the coastal area of Demak and its relation to seawater intrusion and groundwater based on previous research. Understanding the factors that influence water quality in the source area over time is needed to establish appropriate management plans for the protection of groundwater resources and to ensure the safety and health of the beverage.

Assessing groundwater pollution and potential remediation processes in a multi-layer aquifer system

Pumping-induced leakage across aquitards may induce a deterioration of water quality in multi-layer aquifer systems. It is critical to understand long-term trends of water quality parameters when assessing the sustainability of groundwater abstraction. Daily drinking water needs of 2.2 million people in Yinchuan region of northwest China are solely met by groundwater resources, but long-term groundwater withdrawal has created an extensive cone of depression (294 km2 in area) in confined aquifer causing increased vertical recharge. In this study, a model was established and calibrated with head data, then was incorporated with field tracer tests to provide key information on the hydro-dispersive characteristics of the contaminant for assessing both the current and future state of the aquifer system. The results confirmed a close association between water quality deterioration and high downward fluxes of high chloride groundwater, most notably near the center of the cone of depression. On a temporal scale, water quality degradation remains slow, largely due to the high, pre-existing storage of good quality water. Modeling suggests that the water quality in the upper confined aquifer will lose its potability over a 25 km2 and 50 km2 area within 200 years under the current and intensified pumping conditions, respectively. Elevated chloride values were also detected toward the east of the cone, highlighting the impact of hydrological settings on the vertical groundwater flow. Modeling of potential aquifer remediation shows an even slower response with a further 250 years or more required for potability to be restored in affected areas. The findings can provide valuable guidance to for decision makers and support the sustainable management of aquifer exploitation.

Modeling of land subsidence caused by groundwater withdrawal in Konya Closed Basin, Turkey

Abstract. Land subsidence is a threat that occurs worldwide as a result of the withdrawal of fluid and also underground mining. The subsidence is mainly due to excessive groundwater withdrawal from certain types of rocks, such as fine-grained sediments. Mitigating the effects of land subsidence generally requires careful observations of the temporal change in groundwater level and ideally modeling of groundwater flow and subsidence. In Turkey, land subsidence is a crucial issue in the Konya Closed Basin. When simulating the effect of long-term groundwater withdrawal on the spatial variation of subsidence rates, various coupled numerical groundwater-flow and subsidence models have been used. Also, GPS, InSAR and ENVISAT SAR images have been used for verification of the models' parameters. In the work reported here, a novel numerical solution based on consolidation theory was developed in MATLAB to predict the land subsidence of the Konya Closed Basin. In order to adjust the model to the local conditions, historical data from the study area for the years 2011–2014 were used. The presented solution allowed for subsidence model development which can support the prediction of the ground movement for the Konya Closed Basin in Turkey.

Spatiotemporal Evolution of Land Subsidence in the Beijing Plain 2003–2015 Using Persistent Scatterer Interferometry (PSI) with Multi-Source SAR Data

Land subsidence is one of the most important geological hazards in Beijing, China, and its scope and magnitude have been growing rapidly over the past few decades, mainly due to long-term groundwater withdrawal. Interferometric Synthetic Aperture Radar (InSAR) has been used to monitor the deformation in Beijing, but there is a lack of analysis of the long-term spatiotemporal evolution of land subsidence. This study focused on detecting and characterizing spatiotemporal changes in subsidence in the Beijing Plain by using Persistent Scatterer Interferometry (PSI) and geographic spatial analysis. Land subsidence during 2003–2015 was monitored by using ENVISAT ASAR (2003–2010), RADARSAT-2 (2011–2015) and TerraSAR-X (2010–2015) images, with results that are consistent with independent leveling measurements. The radar-based deformation velocity ranged from −136.9 to +15.2 mm/year during 2003–2010, and −149.4 to +8.9 mm/year during 2011–2015 relative to the reference point. The main subsidence areas include Chaoyang, Tongzhou, Shunyi and Changping districts, where seven subsidence bowls were observed between 2003 and 2015. Equal Fan Analysis Method (EFAM) shows that the maximum extensive direction was eastward, with a growing speed of 11.30 km2/year. Areas of differential subsidence were mostly located at the boundaries of the seven subsidence bowls, as indicated by the subsidence rate slope. Notably, the area of greatest subsidence was generally consistent with the patterns of groundwater decline in the Beijing Plain.

Fully coupled three-dimensional nonlinear numerical simulation of pumping-induced land movement

Excessive groundwater extraction can cause aquifer systems to move three-dimensionally. Based on the equilibrium of soil skeleton and continuity of groundwater flow, a fully coupled nonlinear three-dimensional mathematical model has been constructed, which incorporates the prevalent nonlinear mechanical and hydraulic properties of aquifer systems. The horizontal and vertical displacements with regard to nonlinear mechanical properties are obviously less than those results with linear stress–strain relationship, and the discrepancy between them increases with the elapsed time. Compared with the results with regard to the constant hydraulic properties, the horizontal and vertical displacement and the drawdown with nonlinear hydraulic conductivity increase. The discrepancy between the results with and without nonlinear hydraulic properties also increases with the elapsed time. For the ideal aquifer systems addressed in this study, horizontal displacement is predominant when groundwater is pumped from aquifer units. The horizontal strain is compressive within the zone contiguous to the pumping well, and it is tensile beyond that. However, the horizontal strain, especially the tensile strain, is negligible. Such small tensile strain cannot result in tensile stress because there is original compressive stress in soils. The nonlinear mechanical and hydraulic properties of aquifer systems have clear impacts on the numerical simulation of the displacement and the pore water pressure in hydrostratigraphic units, and their impacts increase with pumping time. They should be considered in land movement simulation due to long-term groundwater withdrawal.

Ground Subsidence in the Beijing-Tianjin-Hebei Region from 1992 to 2014 Revealed by Multiple SAR Stacks

The coordinated development of the Beijing-Tianjin-Hebei has become a national strategy with Beijing and Tianjin as twin engines driving the regional development. However, the Beijing-Tianjin-Hebei region has suffered dramatic ground subsidence during last two to three decades, mainly due to long-term groundwater withdrawal. Although, annual spirit leveling has been conducted routinely in some parts of Beijing and Tianjin, and InSAR technique has also been used to monitor ground subsidence in some local areas of the region, there is a lack of a complete survey of ground subsidence over the whole region. In this paper, we report a research on mapping ground subsidence in the Beijing-Tianjin-Hebei region over a long time span from 1992 to 2014. Three SAR datasets from four satellites are used: ERS-1/2 SAR images from 1992 to 2000, ENVISAT ASAR images from 2003 to 2010, and RADARSAT-2 images from 2012 to 2014. An improved multi-temporal InSAR method, namely “Multiple-master Coherent Target Small-Baseline InSAR” (MCTSB-InSAR), has been developed to process the datasets. A unique feature of MCTSB-InSAR is the adjustment process useful for wide area monitoring which provides an integrated solution for both calibration of InSAR-derived deformation and the harmonization of the deformation estimates from overlapping SAR frames. Three maps of the subsidence rate corresponding to the three periods over the wide Beijing-Tianjin-Hebei region are generated, with respective accuracy of 8.7 mm/year (1992–2000), 4.7 mm/year (2003–2010), and 5.4 mm/year (2012–2014) validated by more than 120 leveling measurements. The spatial-temporal characteristics of the development of ground subsidence in Beijing and Tianjin are analyzed. This research represents a first-ever effort on mapping ground subsidence over very large area and over long time span in China. The result is of significance to serve the decision-making on ground subsidence mitigation in the Beijing-Tianjin-Hebei region.

Visco-elasto-plastic compaction of aquitards due to groundwater withdrawal in Shanghai, China

Long-term excessive groundwater withdrawal can cause aquifer systems to compact, and land subsidence ensues. The compaction of aquitards lags behind the change of groundwater level in adjacent aquifers, which is attributed to low hydraulic conductivity and great creep deformation of aquitards. Under the condition of groundwater withdrawal, aquitard clays may compact visco-elastically, elasto-plastically or visco-elasto-plastically, depending on the effective stress history they have experienced. Laboratory data manifest that aquitard clays have a similar constitutive relationship to aquifer sands, therefore the double-yielding visco-elasto-plastic mechanical model proposed for aquifer sands is applicable to aquitard clays. A fully coupled one-dimensional visco-elasto-plastic compaction model is constructed for aquitards to predict their compaction by integrating the double-yielding mechanical model with the flow governing equation of groundwater. The comprehensive compaction model not only makes the groundwater flow and soil deformation coupled, but also takes into account the complex deformation characteristics of aquitard units under long-term groundwater withdrawal, such as creep and plastic deformation under reloading.

Numerical simulation of artificial groundwater recharge for controlling land subsidence

Shanghai, a coastal city situated in the southern part of the Yangtze Delta, China, is experiencing a land subsidence problem due to the rapid development of construction and long-term groundwater withdrawal. Artificial groundwater recharge is considered to be an effective method to solve this problem. However, the stress-strain process in the aquifer and the surrounding ground is much complex rather than the traditional elastic model. In this study, the stress-strain process is considered to relate to the soil behavior under cyclic loading due to the artificial recharge. Because of the complex process, the Subloading Cam-clay model, which can reflect the soil compression and the nonlinear characteristics under cyclic loading condition, is employed. A site test of shallow groundwater recharge is conducted in a Shanghai aquifer to verify the proposed model. The comparison is made between the ground displacements of the test site and the numerical results. The results show that the Subloading Cam-clay model adopted in this paper can accurately simulate the land subsidence rebound by artificial recharge. Furthermore, both the test and numerical results demonstrated that artificial recharge is an effective method to control the land subsidence.

Compaction of aquifer units under complex patterns of changing groundwater level

Long-term groundwater withdrawal has caused severe land subsidence in Shanghai, in which compaction of aquifer units has taken an important role. The compaction characteristics of aquifer units are closely related to the changing patterns of groundwater levels the units have experienced. They may be elastic, elasto-plastic, visco-elastic, or visco-elasto-plastic. Several compaction models are discussed and used to calculate the compaction of the aquifer units in Shanghai. Compared with other models, it is found that double-yielding visco-elasto-plastic model can capture the compaction characteristics of aquifer units and more reasonably simulate the compaction of aquifer unit under complex changing patterns of groundwater level. In particular, the double-yielding model can describe the plastic compaction when the average groundwater level declines but is higher than the historically lowest level and the obvious visco-plastic compaction when the groundwater level is lower than the historically lowest level, which is a popular deformation characteristic for aquifer units in Shanghai.

Mechanical modeling of aquifer sands under long-term groundwater withdrawal

Long-term excessive groundwater withdrawal causes severe land subsidence and considerable economic loss. During the period of land subsidence, aquifer sands present complex deformation characteristics. Field data in the Southern Yangtse Delta, China have shown that the deformation characteristics of aquifer sands are closely related to the changing patterns of groundwater level the aquifer units have experienced. When the groundwater level fluctuates yearly within a certain range, the aquifer unit behaves primarily as an elastic material. When the groundwater level rises and falls alternatively with the average decreasing but higher than the previous lowest value the unit has experienced, the aquifer unit behaves primarily as a visco-elastic and elasto-plastic material. However, when the average level decreases and is lower than the previous lowest value the unit has experienced, the aquifer unit behaves primarily as a visco-elastic, elasto-plastic, and visco-plastic material. The plastic and creep deformation of aquifer sands is also proved through laboratory tests. With the increasing cycle number of loading, the creep and plastic deformation decreases and the expansion under unloading is closer to the compression under loading in a single cycle. On the basis of field and laboratory data, a new mechanical model is constructed, which can describe various kinds of deformation characteristics under different changing patterns of groundwater level, including elastic, visco-elastic, plastic, and visco-plastic deformation. The model includes two yielding stresses and six parameters. When the appropriate field data are available, the six parameters of the model can be determined through graphic methods. Then the deformation of aquifer units can be calculated if the changing groundwater level is known.

上覆厚层滨海沉积物的玄武岩岛含水层中淡水透镜体的厚度变化

Freshwater-lens thickness and long-term changes in freshwater volume in coastal aquifers are commonly assessed through repeated measurement of salinity profiles from monitor wells that penetrate into underlying salt water. In Hawaii, the thickest measured freshwater lens is currently 262 m in dike-free, volcanic-rock aquifers that are overlain by thick coastal sediments. The midpoint depth (depth where salinity is 50% salt water) between freshwater and salt water can serve as an indicator for freshwater thickness. Most measured midpoints have risen over the past 40 years, indicating a shrinking lens. The mean rate of rise of the midpoint from 1999–2009 varied locally, with faster rates in highly developed areas (1.0 m/year) and slower rates in less developed areas (0.5 m/year). The thinning of the freshwater lenses is the result of long-term groundwater withdrawal and reduced recharge. Freshwater/salt-water interface locations predicted from measured water levels and the Ghyben-Herzberg principle may be deeper than measured midpoints during some periods and shallower during other periods, although depths may differ up to 100 m in some cases. Moreover, changes in the midpoint are slower than changes in water level. Thus, water levels may not be a reliable indicator of the amount of freshwater in a coastal aquifer.