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A total of 14 extensometers were installed in Houston-Galveston Region, Texas, USA, at 12 locations to record compaction. The earliest extensometer began to record compaction in 1973. Records from three of the extensometers installed at Baytown (Shallow and Deep) and Pasadena exhibit anomalous subsidence from 2009 to 2017. The maximum compaction occurred around 2014 with Baytown Shallow recording 164 mm, Baytown Deep 72 mm, and Pasadena 135 mm. The anomalous subsidence exhibits features not related to primary consolidation subsidence (PCS) and secondary consolidation subsidence (SCS) of the Gulf Coast Aquifer System (GCAS). Groundwater level records at the extensometer locations indicate that the anomalous subsidence is not related to groundwater exploitation and creep of the GCAS in this region. Analysis of compaction data for the three sites indicates that the subsidence is partially elastic. Salt dome growth/evolution resulting in activation/reactivation of subsurface and surface faults is proposed as the mechanism responsible for the anomalous subsidence.
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Coupled Stress-Dependent Groundwater Flow-Deformation Model to Predict Land Subsidence in Basins with Highly Compressible Deposits
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 andMODFLOW-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.
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- Award ID(s):
- 1832065
- PAR ID:
- 10168032
- Date Published:
- Journal Name:
- Hydrology
- Volume:
- 6
- Issue:
- 78
- ISSN:
- 2306-5338
- Page Range / eLocation ID:
- 1-17
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/hydrology6030078
