Abstract
In the current context of climate change, improving groundwater monitoring and management is an important issue for human communities in arid environments. The exploitation of groundwater resources can trigger land subsidence producing damage in urban structures and infrastructures. Alto Guadalentín aquifer system in SE Spain has been exploited since 1960 producing an average piezometric level drop of 150 m. This work presents a groundwater model that reproduces groundwater evolution during 52 years with an average error below 10%. The geometry of the model was improved introducing a layer of less permeable and deformable soft soils derived from InSAR deformation and borehole data. The resulting aquifer system history of the piezometric level has been compared with ENVISAT deformation data to calculate a first-order relationship between groundwater changes, soft soil thickness, and surface deformation. This relationship has been validated with the displacement data from ERS and Cosmo-SkyMed satellites. The resulting regression function is then used as an empirical subsidence model to estimate a first approximation of the deformation of the aquifer system since the beginning of the groundwater extraction, reaching 1 to 5.5 m in 52 years. These rough estimations highlight the limitations of the proposed empirical model, requiring the implementation of a coupled hydrogeomechanical model.
Highlights
Aquifer overexploitation and groundwater reservoirs depletion represent a problem impacting large areas worldwide [1, 2], especially over arid and semiarid areas
The Alto Guadalentın basin (Figure 1) is an intramontane sedimentary NE-SW-oriented basin limited by Torrecilla range to the North-West and Almenara range to the SouthEast and contains an aquifer system that is hydraulically connected to the Bajo Guadalentın aquifer system
Modeling results present the evolution of the piezometric levels throughout 52 years (1960–2012) across the Alto Guadalentın basin and how the actions on the aquifer have affected them
Summary
Aquifer overexploitation and groundwater reservoirs depletion represent a problem impacting large areas worldwide [1, 2], especially over arid and semiarid areas. The use of numerical groundwater flow models to reproduce the hydrodynamic behavior of an area and simulate spatial and temporal changes in piezometric levels, together with synthetic aperture radar differential interferometry (DInSAR) that detects surface movements, allows a global approach to assess main aquifer threats Both techniques have been used to understand subsidence related to groundwater withdrawal [12] and calibrate hydrogeological and geomechanical parameters [13]. SAR-derived deformation series has been compared with piezometric change data and soft soils thickness data in order to evaluate a first-order relationship between them This is the first time that results of a calibrated transient groundwater model, simulating more than 50 years of the Alto Guadalentın aquifer behavior, have been analyzed to understand and quantify the associated subsidence. Subsidence measurements derived from SAR data have contributed to improving the conceptual and physical groundwater model
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