scholarly journals Coupled Stress-Dependent Groundwater Flow-Deformation Model to Predict Land Subsidence in Basins with Highly Compressible Deposits

Hydrology ◽  
2019 ◽  
Vol 6 (3) ◽  
pp. 78
Author(s):  
Rashvand ◽  
Li ◽  
Liu
Keyword(s):  
Hydraulic Conductivity ◽  
Groundwater Flow ◽  
Land Subsidence ◽  
Three Dimensional ◽  
Deformation Model ◽  
Specific Storage ◽  
Aquifer System ◽  
Horizontal Strain ◽  
Stress Dependent ◽  
Coupled Stress

In this study, a stress-dependent groundwater model, MODFLOW-SD, has been developed and coupled with the nonlinear subsidence model, NDIS, to predict vertical deformation occurring in basins with highly compressible deposits. The MODFLOW-SD is a modified version of MODFLOW (the USGS Modular Three-Dimensional Groundwater Flow Model) with two new packages, NONK and NONS, to update hydraulic conductivity and skeletal specific storage due to change in effective stress. The NDIS package was developed based on Darcy–Gersevanov Law and bulk flux to model land subsidence. Results of sample simulations run for a conceptual model showed that hydraulic heads calculated by MODFLOW significantly overestimated for confining units and slightly underestimated for aquifer ones. Moreover, it showed that applied stress due to pumping changed initially homogeneous layers to be heterogeneous ones. Comparison of vertical deformations calculated by NDIS and MODFLOW-SUB showed that neglecting horizontal strain and stress-dependency of aquifer parameters can overestimate future subsidence. Furthermore, compared to the SUB (Subsidence and Aquifer-System Compaction) package, NDIS is more likely to provide a more accurate compaction model for a complex aquifer system with vertically variable compression (Cc), recompression (Cr), and hydraulic conductivity change (Ck) indices.

scholarly journals Approximate analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

2016 ◽  
Vol 20 (1) ◽  
pp. 55-71 ◽  
Author(s):  
C.-S. Huang ◽  
J.-J. Chen ◽  
H.-D. Yeh
Keyword(s):  
Groundwater Flow ◽  
Integral Transform ◽  
Three Dimensional ◽  
Vertical Component ◽  
Hydraulic Head ◽  
Unconfined Aquifer ◽  
Specific Yield ◽  
Specific Storage ◽  
Sink Term ◽  
Radial Collector Well

Abstract. This study develops a three-dimensional (3-D) mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The streams with low-permeability streambeds fully penetrate the aquifer. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. Robin boundary conditions are adopted to describe fluxes across the streambeds. The head solution for the point sink is derived by applying the methods of finite integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length, and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow for the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

scholarly journals Analysis of three-dimensional groundwater flow toward a radial collector well in a finite-extent unconfined aquifer

2015 ◽  
Vol 12 (8) ◽  
pp. 7503-7540 ◽  
Author(s):  
C.-S. Huang ◽  
J.-J. Chen ◽  
H.-D. Yeh
Keyword(s):  
Groundwater Flow ◽  
Integral Transform ◽  
Three Dimensional ◽  
Vertical Component ◽  
Hydraulic Head ◽  
Unconfined Aquifer ◽  
Specific Yield ◽  
Specific Storage ◽  
Sink Term ◽  
Radial Collector Well

Abstract. This study develops a three-dimensional mathematical model for describing transient hydraulic head distributions due to pumping at a radial collector well (RCW) in a rectangular confined or unconfined aquifer bounded by two parallel streams and no-flow boundaries. The governing equation with a point-sink term is employed. A first-order free surface equation delineating the water table decline induced by the well is considered. The head solution for the point sink is derived by applying the methods of double-integral transform and Laplace transform. The head solution for a RCW is obtained by integrating the point-sink solution along the laterals of the RCW and then dividing the integration result by the sum of lateral lengths. On the basis of Darcy's law and head distributions along the streams, the solution for the stream depletion rate (SDR) can also be developed. With the aid of the head and SDR solutions, the sensitivity analysis can then be performed to explore the response of the hydraulic head to the change in a specific parameter such as the horizontal and vertical hydraulic conductivities, streambed permeability, specific storage, specific yield, lateral length and well depth. Spatial head distributions subject to the anisotropy of aquifer hydraulic conductivities are analyzed. A quantitative criterion is provided to identify whether groundwater flow at a specific region is 3-D or 2-D without the vertical component. In addition, another criterion is also given to allow the neglect of vertical flow effect on SDR. Conventional 2-D flow models can be used to provide accurate head and SDR predictions if satisfying these two criteria.

scholarly journals Extensometer forensics: what can the data really tell us?

2019 ◽  
Vol 28 (2) ◽  
pp. 637-655
Author(s):  
Thomas J. Burbey
Keyword(s):  
Hydraulic Conductivity ◽  
Land Subsidence ◽  
Numerical Models ◽  
Water Levels ◽  
Depth Interval ◽  
Key Factors ◽  
Specific Storage ◽  
Las Vegas Valley ◽  
Multiple Frequencies ◽  
Parameter Values

AbstractExtensometer data have an advantage over satellite-based data for monitoring land subsidence in that extensometer data provide continuous measurements (hourly or better temporal resolution) at very high precision (several tens of microns) over a known depth interval; the latter is important for isolating groundwater pumping from other causes of land subsidence attributed to tectonics or eustatic adjustments in the Earth’s crust. This investigation aims to identify a semi-analytical procedure for quantifying aquifer and aquitard properties from a single extensometer record in lieu of the time-consuming development of more complex numerical models to quantify and constrain these parameter values. In spite of a limited 12-year record and the fact that water levels both decline and increase on an annual basis, this study successfully and reasonably estimated both aquifer and aquitard parameters at the Lorenzi extensometer site in Las Vegas Valley, Nevada (USA), when compared to the estimates developed numerically. The key factors that allow for estimates of elastic and inelastic skeletal-specific storage and hydraulic conductivity of the aquitards and elastic specific storage and hydraulic conductivity of the intervening aquifers is the presence of pumping cycles at multiple frequencies, and measured heads at all the aquifer units covered in the extensometer record. There is an inherent assumption that the aquitards possess the same hydrologic characteristics and are homogeneous and isotropic. This assumption is also a usual limitation in numerical modeling of these settings because of the complex temporal head relationships occurring within the aquitards that are rarely, if ever, measured.

scholarly journals 3-D land subsidence simulation using the NDIS package for MODFLOW

2015 ◽  
Vol 372 ◽  
pp. 437-442
Author(s):  
D. H. Kang ◽  
J. Li
Keyword(s):  
Land Subsidence ◽  
Vertical Displacement ◽  
Specific Storage ◽  
Horizontal Movement ◽  
Pumping Rate ◽  
Aquifer System ◽  
Pumping Wells ◽  
Single Well ◽  
Vertical Subsidence ◽  
Applied Stresses

Abstract. The standard subsidence package for MODFLOW, MODFLOW-SUB simulates aquifer-system compaction and subsidence assuming that only 1-D-vertical displacement of the aquifer system occurs in response to applied stresses such as drawdowns accompanying groundwater extraction. In the present paper, 3-D movement of an aquifer system in responses to one or more pumping wells is considered using the new aquifer-system deformation package for MODFLOW, NDIS. The simulation of aquifer- system 3-D movement using NDIS was conducted with a stress or hydraulic head dependent specific storage coefficient to simulate nonlinear deformation behavior of aquifer-system sedimentary materials. NDIS's numerical simulation for aquifer horizontal movement is consistent with an analytic solution for horizontal motion in response to pumping from a leaky confined aquifer (Li, 2007). For purposes of comparison, vertical subsidence of the aquifer system in response to groundwater pumping is simulated by the both the NDIS and MODFLOW-SUB models. The results of the simulations show that land subsidence simulated by MODFLOW-SUB is significantly larger and less sensitive to pumping rate and time than that simulated by NDIS. The NDIS simulations also suggest that if the total pumpage is the same, pumping from a single well may induce more land subsidence than pumping from multiple wells.

Using Groundwater Flow Modelling for Investigation of Land Subsidence in the Konya Closed Basin (Turkey)

2018 ◽  
pp. 569-590
Author(s):  
Naciye Nur Özyurt ◽  
Pınar Avcı ◽  
Celal Serdar Bayarı
Keyword(s):  
Groundwater Flow ◽  
Land Subsidence ◽  
Sole Source ◽  
Central Anatolia ◽  
Flow Modeling ◽  
Groundwater Abstraction ◽  
Groundwater Flow Modeling ◽  
Aquifer System ◽  
Closed Basin ◽  
Groundwater Flow Modelling

Land subsidence which is defined as gradual settling or sudden collapse of Earth's surface, is a geohazard phenomenon that occurs worldwide. Land subsidence occurs in time mainly due to excessive groundwater abstraction. This problem occurs usually in semi-arid regions where the groundwater is the sole source of water. Eliminating the adverse effects of land subsidence requires careful observations on the temporal change of elevation coupled with groundwater flow modeling. In this study, numerical groundwater flow modeling technique is applied to a confined aquifer system in the Konya Subbasin of Konya Closed Basin (KCB), central Anatolia, Turkey. Groundwater head in the KCB has been declining with a rate of about 1m/year since early 1980s. Recent GPS observations reveal subsidence rates of 22 mm/year over the southern part of KCB. MODFLOW numerical groundwater flow model coupled with subsidence (SUB) package is used to simulate the effect of long term groundwater abstraction on the spatial variation of subsidence rates.

scholarly journals Fine Characterization of the Effects of Aquifer Heterogeneity on Solute Transport: A Numerical Sandbox Experiment

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2295
Author(s):  
Zhang ◽  
Wu ◽  
Hu ◽  
Yeh ◽  
Hao ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Solute Transport ◽  
A Priori ◽  
Specific Storage ◽  
Aquifer Heterogeneity ◽  
Aquifer System ◽  
Modified Method ◽  
Hydrogeological Parameters ◽  
Geological Information

Hydraulic conductivity (K) and the specific storage coefficient (S) are among the most important hydrogeological parameters of an aquifer. Traditionally, the hydrogeological parameters of a field aquifer system are mainly determined through a range of experiments that are both time-consuming and of poor operability. To accurately characterize aquifer heterogeneity, a synthetic sandbox is constructed using VSAFT2 (Variably Saturated Flow and Transport utilizing the Modified Method of Characteristics, in 2D) as a reference aquifer system by incorporating multilevel a priori geologic information into the sandbox configuration. The spatial distribution of the field of hydraulic conductivity (i.e., K) is inversely obtained by hydraulic tomography (HT). Then HT is compared with traditional kriging-estimated method in the fine characterization of aquifer heterogeneity, and the optimal K field is eventually selected to predict the solute transport. The influence of the number of pumping cycles on the accuracy of heterogeneity characterization is also discussed. The results show that the accuracy of the inversely obtained K field is improved with the increased number of pumping cycles. When incorporating multilevel a priori geological information, HT can characterize aquifer heterogeneity more finely than traditional kriging, and there is also a very good fitting of solute transport between the optimally estimated K field and the reference K field. Our study highlights the importance of the fine characterization of aquifer heterogeneity for the prediction of solute transport.

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