Clustering Groundwater Level Time Series of the Exploited Almonte-Marismas Aquifer in Southwest Spain

Groundwater resources are regularly the principal water supply in semiarid and arid climate areas. However, groundwater levels (GWL) in semiarid aquifers are suffering a general decrease because of anthropic exploitation of aquifers and the repercussions of climate change. Effective groundwater management strategies require a deep characterization of GWL fluctuations, in order to identify individual behaviors and triggering factors. In September 2019, the Guadalquivir River Basin Authority (CHG) declared that there was over-exploitation in three of the five groundwater bodies of the Almonte-Marismas aquifer, Southwest Spain. For that reason, it is critical to understand GWL dynamics in this aquifer before the new Spanish Water Resources Management Plans (2021–2027) are developed. The application of GWL series clustering in hydrogeology has grown over the past few years, as it is an extraordinary tool that promptly provides a GWL classification; each group can be related to different responses of a complex aquifer under any external change. In this work, GWL time series from 160 piezometers were analyzed for the period 1975 to 2016 and, after data pre-processing, 24 piezometers were selected for clustering with k-means (static) and time series (dynamic) clustering techniques. Six and seven groups (k) were chosen to apply k-means. Six characterized types of hydrodynamic behaviors were obtained with time series clustering (TSC). Number of clusters were related to diverse affections of water exploitation depending on soil uses and hydrogeological spatial distribution parameters. TSC enabled us to distinguish local areas with high hydrodynamic disturbance and to highlight a quantitative drop of GWL during the studied period

Applying 3D Geostatistical Simulation to Improve the Groundwater Management Modelling of Sedimentary Aquifers: The Case of Doñana (Southwest Spain)

Mathematical groundwater modelling with homogeneous permeability zones has been used for decades to manage water resources in the Almonte-Marismas aquifer (southwest Spain). This is a highly heterogeneous detrital aquifer which supports valuable ecological systems in the Doñana National Park. The present study demonstrates that it is possible to better characterize this heterogeneity by numerical discretization of the geophysical and lithological data available. We identified six hydrofacies whose spatial characteristics were quantified with indicator variogram modelling. Sequential Indicator Simulation then made it possible to construct a 3D geological model. Finally, this detailed model was included in MODFLOW through the Model Muse interface. This final process is still a challenge due to the difficulty of downscaling to a handy numerical modelling scale. New piezometric surfaces and water budgets were obtained. The classical model with zones and the model with 3D simulation were compared to confirm that, for management purposes, the effort of improving the geological heterogeneities is worthwhile. This paper also highlights the relevance of including subsurface heterogeneities within a real groundwater management model in the present global change scenario

Subsidence activity maps derived from DInSAR data: Orihuela case study

A new methodology is proposed to produce subsidence activity maps based on the geostatistical analysis of persistent scatterer interferometry (PSI) data. PSI displacement measurements are interpolated based on conditional Sequential Gaussian Simulation (SGS) to calculate multiple equiprobable realizations of subsidence. The result from this process is a series of interpolated subsidence values, with an estimation of the spatial variability and a confidence level on the interpolation. These maps complement the PSI displacement map, improving the identification of wide subsiding areas at a regional scale. At a local scale, they can be used to identify buildings susceptible to suffer subsidence related damages. In order to do so, it is necessary to calculate the maximum differential settlement and the maximum angular distortion for each building of the study area. Based on PSI-derived parameters those buildings in which the serviceability limit state has been exceeded, and where in situ forensic analysis should be made, can be automatically identified. This methodology has been tested in the city of Orihuela (SE Spain) for the study of historical buildings damaged during the last two decades by subsidence due to aquifer overexploitation. The qualitative evaluation of the results from the methodology carried out in buildings where damages have been reported shows a success rate of 100%.The European Space Agency (ESA) Terrafirma project has funded all the SAR data processing with the SPN technique. Additionally, this work has been partially financed by DORIS project (Ground deformation risk scenarios: an advanced assessment service) funded by the EC-GMES-FP7 initiative (grant agreement no. 242212), and the Spanish Geological and Mining Institute (IGME). This work has been also supported by the Spanish Ministry of Science and Research (MICINN) under project TEC2011-28201-C02-02 and EU FEDER

Flood Damage Analysis: First Floor Elevation Uncertainty Resulting from LiDAR-Derived Digital Surface Models

The use of high resolution ground-based light detection and ranging (LiDAR) datasets provides spatial density and vertical precision for obtaining highly accurate Digital Surface Models (DSMs). As a result, the reliability of flood damage analysis has improved significantly, owing to the increased accuracy of hydrodynamic models. In addition, considerable error reduction has been achieved in the estimation of first floor elevation, which is a critical parameter for determining structural and content damages in buildings. However, as with any discrete measurement technique, LiDAR data contain object space ambiguities, especially in urban areas where the presence of buildings and the floodplain gives rise to a highly complex landscape that is largely corrected by using ancillary information based on the addition of breaklines to a triangulated irregular network (TIN). The present study provides a methodological approach for assessing uncertainty regarding first floor elevation. This is based on: (i) generation an urban TIN from LiDAR data with a density of 0.5 points·m−2, complemented with the river bathymetry obtained from a field survey with a density of 0.3 points·m−2. The TIN was subsequently improved by adding breaklines and was finally transformed to a raster with a spatial resolution of 2 m; (ii) implementation of a two-dimensional (2D) hydrodynamic model based on the 500-year flood return period. The high resolution DSM obtained in the previous step, facilitated addressing the modelling, since it represented suitable urban features influencing hydraulics (e.g., streets and buildings); and (iii) determination of first floor elevation uncertainty within the 500-year flood zone by performing Monte Carlo simulations based on geostatistics and 1997 control elevation points in order to assess error. Deviations in first floor elevation (average: 0.56 m and standard deviation: 0.33 m) show that this parameter has to be neatly characterized in order to obtain reliable assessments of flood damage assessments and implement realistic risk managementThis research as well as the costs for covering the publication in open access were funded by the MARCoNI (CGL2013-42728-R) project. The authors also acknowledge to the National Geographic Institute of Spain for providing LiDAR data and to the Spanish cadastre for supplying the elevation points used to characterize error in first floor elevation.Bodoque, JM.; Guardiola-Albert, C.; Aroca-Jiménez, E.; Eguibar Galán, MÁ.; Martínez-Chenoll, L. (2016). Flood Damage Analysis: First Floor Elevation Uncertainty Resulting from LiDAR-Derived Digital Surface Models. Remote Sensing. 8(7). https://doi.org/10.3390/rs80706048

The Manning’s Roughness Coefficient Calibration Method to Improve Flood Hazard Analysis in the Absence of River Bathymetric Data: Application to the Urban Historical Zamora City Centre in Spain

The accurate estimation of flood risk depends on, among other factors, a correct delineation of the floodable area and its associated hydrodynamic parameters. This characterization becomes fundamental in the flood hazard analyses that are carried out in urban areas. To achieve this objective, it is necessary to have a correct characterization of the topography, both inside the riverbed (bathymetry) and outside it. Outside the riverbed, the LiDAR data led to an important improvement, but not so inside the riverbed. To overcome these deficiencies, different models with simplified bathymetry or modified inflow hydrographs were used. Here, we present a model that is based upon the calibration of the Manning’s n value inside the riverbed. The use of abnormally low Manning’s n values made it possible to reproduce both the extent of the flooded area and the flow depth value within it (outside the riverbed) in an acceptable manner. The reduction in the average error in the flow depth value from 50–75 cm (models without bathymetry and “natural” Manning’s n values) to only about 10 cm (models without bathymetry and “calibrated” Manning’s n values), was propagated towards a reduction in the estimation of direct flood damage, which fell from 25–30% to about 5%

Selecting Suitable MODFLOW Packages to Model Pond–Groundwater Relations Using a Regional Model

In large-scale regional models, used for the management of underground resources, it is quite common to find that relationships between the regional aquifer and small wetlands are not included. These models do not consider this connection because of the small amount of water involved, but they should consider the potential for significant ecological impacts if the groundwater resources in the ecosystems associated with these wetlands are mismanaged. The main objective of this work is to investigate the possibilities offered by MODFLOW LGR-V2 to represent (at small scale) the Santa Olalla pond, located in the Doñana Natural Park (South of Spain), and its relationship with the Almonte-Marismas regional aquifer. As a secondary objective, we propose to investigate the advantages and disadvantages that DRAIN, RIVER and LAKE MODFLOW packages offer within the MODFLOW LGR-V2 discretizations. The drain boundary condition with a coarse discretization implemented through ModelMuse allows the most adequate performance of the groundwater levels in the environment of the pond. However, when using lake boundary condition, the use of the MODFLOW LGR-V2 version is particularly useful. The present work also gives some guidelines to employ these packages with the MODFLOW graphical user’s interface, ModelMuse 4.2

Evaluation of the potential of InSAR time series to study the spatio-temporal evolution of piezometric levels in the Madrid aquifer

The Tertiary detritic aquifer of Madrid (TDAM), with an average thickness of 1500 m and a heterogeneous, anisotropic structure, supplies water to Madrid, the most populated city of Spain (3.2 million inhabitants in the metropolitan area). Besides its complex structure, a previous work focused in the north-northwest of Madrid city showed that the aquifer behaves quasi elastically trough extraction/recovery cycles and ground uplifting during recovery periods compensates most of the ground subsidence measured during previous extraction periods (Ezquerro et al., 2014). Therefore, the relationship between ground deformation and groundwater level through time can be simulated using simple elastic models. In this work, we model the temporal evolution of the piezometric level in 19 wells of the TDAM in the period 1997–2010. Using InSAR and piezometric time series spanning the studied period, we first estimate the elastic storage coefficient (Ske) for every well. Both, the Ske of each well and the average Ske of all wells, are used to predict hydraulic heads at the different well locations during the study period and compared against the measured hydraulic heads, leading to very similar errors when using the Ske of each well and the average Ske of all wells: 14 and 16 % on average respectively. This result suggests that an average Ske can be used to estimate piezometric level variations in all the points where ground deformation has been measured by InSAR, thus allowing production of piezometric level maps for the different extraction/recovery cycles in the TDAM.This work is supported by the Spanish Ministry of Economy and Competitiveness and EU FEDER funds under projects TEC2011-28201-C02-02, TIN2014-55413-C2-2-P and ESP2013-47780-C2-2-R, by the Ministry of Education, Culture and Sport trough the project PRX14/00100 and by the project 15224/PI/10 from the Regional Agency of Science and Technology in Murcia

Improving multi-technique monitoring using Sentinel-1 and Cosmo-SkyMed data and upgrading groundwater model capabilities

Aquifer-systems have become a strategic source of fresh water in the present climatic conditions, especially under stress in arid regions like the Iberian Mediterranean Arc. Understanding the behavior of groundwater reservoirs is crucial to their well-management and mitigation of adverse consequences of overexploitation. In this work, we use space geodetic measurements from satellite interferometric synthetic aperture radar (InSAR) and Global Positioning System (GPS) data, covering the period 2011–2017, to predict and validate the ground surface displacement over the fastest subsiding basin due to groundwater withdrawal in Europe (>10 cm/year). The 2D decomposition of InSAR displacements from Cosmo-SkyMed and Sentinel-1 satellites allows us to detect horizontal deformation towards the basin center, with a maximum displacement of 1.5 cm/year. InSAR results were introduced in a newly developed methodology for aquifer system management to estimate unknown pumping rates for the 2012–2017 period. This study illustrates how the combination of InSAR data, groundwater flow and deformation models can be used to improve the aquifer-systems sustainable management.This work was supported by the Spanish Ministry of Science, Innovation and Universities (MICINN), Spain; the State Agency of Research (AEI), Spain; and European Funds for Regional Development (FEDER), under projects AQUARISK (ESP2013-47780-C2-2-R), TEMUSA (TEC2017-85244-C2-1-P) and STAR-EO (TIN2014-55413-C2-2-P). First author shows gratitude for PhD student contract BES-2014-069076. A first version of this work was written during the research stay of first and second authors in the Università degli Studi di Firenze supported by the Spanish Ministry of Education, Culture and Sport, under fellowships EEBB-I-18-13014 and PRX17/00439, respectively

Imaging land subsidence in the Guadalentín River Basin (SE Spain) using Advanced Differential SAR Interferometry

Aquifer overexploitation can lead to the irreversible loss of groundwater storage caused by the compaction or consolidation of unconsolidated fine-grained sediments resulting in land subsidence. Advanced Differential SAR Interferometry (A-DINSAR) is particularly efficient to monitor progressive ground movements, making it an appropriate method to study depleting aquifers undergoing overexploitation and land subsidence. The Guadalentín River Basin (Murcia, Spain) is a widely recognized subsiding area that exhibits the highest rates of groundwater-related land subsidence recorded in Europe (>10 cm/yr). The basin covers an extension of more than 500 km2 and is underlain by an overexploited aquifer-system formed by two contiguous hydraulically connected units (Alto Guadalentín and Bajo Guadalentín). Although during the last years the piezometric levels have partially stabilized, the ongoing aquifer-system deformation is evident and significant, as revealed by the A-DInSAR analysis presented. In this work, we submit the first vertical and horizontal (E-W) decomposition results of the LOS velocity and displacement time series of the whole Guadalentín Basin obtained from two datasets of Sentinel-1 SAR acquisitions in ascending and descending modes. The images cover the period from 2015 to 2021 and they were processed using the Parallel Small BAseline Subset (P-SBAS) implemented by CNRIREA in the Geohazards Exploitation Platform (GEP) on-demand web tool, which is funded by the European Space Agency. The output ascending and descending measurement points of P-SBAS lie on the same regular grid, which is particularly suited for the geometrical decomposition. Time series displacements are compared to a permanent GNSS station located in the Bajo Guadalentín basin.This study has received funding in framework of the RESERVOIR project (Sustainable groundwater RESources managEment by integrating eaRth observation deriVed monitoring and flOw modelIng Results), funded by the Partnership for Research and Innovation in the Mediterranean Area (PRIMA) programme supported by the European Union (Grant Agreement 1924; https://reservoir-prima.org/). The study has also been supported by the Grant FPU19/03929 (funded by MCIN/AEI/10.13039/501100011033 and by “FSE invests in your future”); the Project CGL2017-83931-C3-3-P (funded by MCIN/ AEI/10.13039/501100011033 and by “ERDF A way of making Europe”); the ESA-MOST China DRAGON-5 Project (ref. 59339) and the SARAI Project PID2020-116540RB-C22 (funded by MCIN/AEI/10.13039/501100011033). Copernicus Sentinel-1 IW SAR data were provided and processed in ESA’s Geohazards Exploitation Platform (GEP), in the framework of the GEP Early Adopters Programme