The LASUGEO project: monitoring LAnd SUbsidence caused by ...
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Xavier DEVLEESCHOUWER 1 , Atefe CHOOPANI 1,2 , Aline MOREAU 2 , Kristine WALRAEVENS 3 , Marc VAN CAMP 3 , Michel VAN CAMP 4 , Kevin GOBRON 4 , Alain DASSARGUES 2 , Philippe ORBAN 2 , Pierre − Yves DECLERCQ 1 1. Royal Belgian Institute of Natural Sciences, Geological Survey of Belgium, Rue Vautier 29, 1000 Brussels, Belgium ([email protected] ; [email protected] ; [email protected]) 2. Liège University, Hydrogeology & Environmental Geology, Urban & Environmental Engineering, allée de la Découverte 9, 4000 Liège, Belgium ([email protected] ; [email protected] ; [email protected]) 3. Gent University, Department of Geology, Krijgslaan 281, S8, 9000 Gent, Belgium ([email protected] ; [email protected]) 4. Royal Observatory of Belgium, Avenue Circulaire, 3, 1080 Brussels, Belgium ([email protected] ; [email protected]) The LASUGEO project: monitoring LAnd SUbsidence caused by Groundwater exploitation through gEOdetic measurements. - PS-InSAR (Interferometric Synthetic Aperture Radar) data allow measuring slow-moving ground deformations with high spatial resolution. - In Belgium, most of the subsidence is related to fluctuations of water pressure in aquifers (Figure 1) (Declercq et al., 2017; 2021). - Any change in pore pressure (or piezometric heads) may induce consolidation if the geological formations are compressible. When groundwater levels and water pressures are restored, a partial rebound (uplift) corresponds to the elastic part of the geomechanical behaviour. - The most sensitive layers contain clay, loam, or peat, ➔ consolidation occurs mostly in the underlying and overlying layers that are often less permeable and more compressible than the aquifer itself. Subsidence is a delayed process occurring as far as the pore pressure variation propagates slowly in the low permeability (aquitard) layers. - The last 30 years PS-InSAR data measures the subsidence or uplift over large-scale areas, that we compare with hydrogeological groundwater and geomechanical models and other geodetic techniques (GPS/GNSS stations, absolute gravimetry). - Targets ➔ he deep aquifer system of western Flanders, the Tertiary aquifer system in Central Flanders, the Antwerp area, the Leuven area, and the Brussels Region. - The vertical land movements will be compared with 1D geomechanical model results. The latter will be performed using geotechnical effective stresses as deduced from the pore pressure distribution from the 3D hydrogeological models (Dassargues et al., 1989, Dassargues 2018). Land Subsidence Simulation in Merchtem and the SW part of Flanders Groundwater Modelling in Leuven Area In Antwerp, four subsidence processes may occur: 1. Natural compaction of recent Holocene Formation 2. Additional settlement of recent Holocene due to backfill overburden along the new docks 3. Saturated-unsaturated consolidation of the backfill material itself 4. Compaction of the most compressible layers, probably in the Boom Formation (Paleocene) and in the Asse clay of the Maldegem Formation (Eocene) due to pore pressure decrease caused by groundwater pumping in the different Cenozoic aquifers. Using the Robust Network Imaging technique proposed by Kreemer et al., (2020), we imaged the VLM resulting from GNSS and PS-InSAR on a 0.01° x 0.01° grid. Because PS-InSAR can present large-scale artifacts, we filtered out the short-wavelength deformation from PS- InSAR using a median filter with a 25 km radius and combined it with large wavelength deformation retrieved by GNSS (Figure 8). This allows quantifying both the large-scale pattern (i.e., Eifel uplift and coastal subsidence) along with the local deformation. Land subsidence is calculated by accumulating the compaction of all layers. The MODFLOW simulator was used as groundwater flow model and the ‘Subsidence and Aquifer-System Compaction’ (SUB) Package was selected for computation of the layer compaction & subsidence. Subsidence in Antwerp area Large-Scale Map of Subsidence over Belgium using PS-InSAR and Robust Network Imaging Abstract In Belgium, most of the identified subsidence areas could be related to piezometric fluctuations in aquifers. Using PS-InSAR data, two areas of significant subsidence are observed in the north of Leuven. In these specific locations, many historical and currently active pumping wells are present. The most important pumping wells are screened in the Brussels Formation. Figure 2. Calculated land subsidence (in mm) in the year 2000 caused by the exploitation of the deep aquifer system (Paleozoic basement and Landenian aquifers). Figure 3. Calculated land subsidence (in mm) in the region around Merchtem and Steenokkerzeel due to pumping in the Ledo-Paniselian and Ypresian aquifer systems (situation after 10 years of pumping at the recent pumping rates). - at least two different zones with dissimilar behaviours: city centre and harbour of Antwerp - differences in land subsidence rates in different zones of the area are linked to dissimilarity in the stability of subsoil - effect of pumping groundwater from deeper layers particularly Oligocene aquifer, which can play an important role in the displacements of the region (Figure 4 and 5) - groundwater model + 1D geomechanical model will bring comprehensive knowledge related to the subsidence processes going on in the area. 12000000 14500000 17000000 19500000 22000000 24500000 août-87 janv.-93 juil.-98 janv.-04 juil.-09 déc.-14 juin-20 Volume (m 3 /year) Date (month-year) Volume of groundwater pumped from the Brusselian aquifer (1990-2020) Figure 6. Evolution of the volume of groundwater pumped from the Brusselian aquifer in the delimited study area around Leuven, Belgium. Figure 7. Computed piezometric map in the Brusselian aquifer. In background, observed piezometric map (VMM, 2016). Control points with a 5 meter error gauge related to the calculated piezometric head compared to the piezometric map. Figure 4. Distribution map of pumping wells over the study area. Figure 5. Drawdown contour map in Oligocene Aquifer during the period 2009-2017. Figure 8. Vertical land motions in Belgium resulting from the combination of PS-InSAR and GNSS data. GNSS position time series from Nevada Geodetic Laboratory. SAR data : ENVISAT date Toward Next Steps The following steps will be accomplished through future steps: 1. Using high resolution TerraSAR-X radar dataset to have more accurate mapping of ground displacement. 2. A 3D groundwater multi-layer model simulating water level under transient state along with a 1D geomechanical model simulating subsidence in those layers will be developed for each target area. 3. Combining all measurements observed by the Global Navigation Satellite System (GNSS) statistic network over Belgium belonging to Nevada Geodetic Laboratory (NGL) with repeated absolute gravity measurements and PS-InSAR measurements to either validate PS- InSAR data or retrieve displacement measurements in those areas where no PS points are observed by the radar sensor. 4. Comparison of results from different techniques to better interpret the causes and effects of ground deformations. 5. Future measurements of land surface displacements will be achived by installing different sets of devices called corner reflectors equipped with professional GNSS stations. Corner reflectors will be illuminated by radar satellite as PS’s and their displacements values will be verified by the GNSS observations attached to them. In the SW of Flanders, between 1920 & 2005, an intensive exploitation of the deep aquifer system (DAS), in the Paleozoic basement and Landenian Formation, has created a regional scale depression cone in the piezometric levels with maximum drawdowns up to 150 m in the basement aquifer and ~100 m in the Landenian Formation. Since 2005 pumping has been restricted but recovery goes very slow because of the limited recharge of these deep layers and even recently the remaining depressions cones are very deep. Simulating of the exploitation history of the DAS and calculating compaction and subsidence shows that subsidence reaches up to 3 cm in a 50 km- wide EW oriented strip (Figure 2). In the Flemish-Brabant province, around Merchtem and Steenokkerzeel, known for its breweries, groundwater exploitation in the Ledo-Paniselian and Ypresian aquifers, but the depression that comes in these layers are local and limited, only a few meters deep. This is insufficient to create significant subsidence, even after a decade of pumping, as the model shows (Figure 3). Land subsidence is less than a cm. A 3D groundwater flow model integrating the different geological formations, the hydrogeological parameters, the stress factors (see Figure 6) and historical data for the area of Leuven has been developed. The model has been calibrated in steady state (Figure 7). The model will be now calibrated in transient conditions and then be coupled with a- geomechanical model for consolidation and rebound calculation. Combining both GNSS and PS-InSAR data to reconstruct vertical land motions over Belgium - GNSS observations allow computing geocentric velocities of a network of GNSS stations separated by a few tens of kilometers. - PS-InSAR data allows deriving the deformation field with a much higher resolution, but relative to an arbitrary local reference. Contact point: Coordinator of the Brain-Belspo funded LASUGEO project: [email protected] and twitter account: LASUGEO1 . Figure 1. Sentinel1-A ascending LOS velocities across part of Belgium showing two main subsidence bowls (in the Merchtem and Antwerp areas)
Transcript of The LASUGEO project: monitoring LAnd SUbsidence caused by ...
Xavier DEVLEESCHOUWER1 Atefe CHOOPANI12 Aline MOREAU2 Kristine WALRAEVENS3 Marc VAN CAMP3
Michel VAN CAMP4 Kevin GOBRON4 Alain DASSARGUES2 Philippe ORBAN2 Pierre minus Yves DECLERCQ1
1 Royal Belgian Institute of Natural Sciences Geological Survey of Belgium Rue Vautier 29 1000 Brussels Belgium (xdevleeschouwernaturalsciencesbe achoopaninaturalsciencesbe pydeclercqnaturalsciencesbe)
2 Liegravege University Hydrogeology amp Environmental Geology Urban amp Environmental Engineering alleacutee de la Deacutecouverte 9 4000 Liegravege Belgium (alinemoreauuliegebe alaindassarguesuliegebe porbanuliegebe)3 Gent University Department of Geology Krijgslaan 281 S8 9000 Gent Belgium (kristinewalraevensugentbe marcvancampugentbe)
4 Royal Observatory of Belgium Avenue Circulaire 3 1080 Brussels Belgium (michelvancampseismologiebe kevingobronomabe)
The LASUGEO project monitoring LAnd SUbsidence caused by Groundwater exploitation through gEOdetic measurements
- PS-InSAR (Interferometric Synthetic Aperture Radar) data allow measuring slow-moving ground deformations with high spatialresolution
- In Belgium most of the subsidence is related to fluctuations of water pressure in aquifers (Figure 1) (Declercq et al 2017 2021)- Any change in pore pressure (or piezometric heads) may induce consolidation if the geological formations are compressible Whengroundwater levels and water pressures are restored a partial rebound (uplift) corresponds to the elastic part of the geomechanicalbehaviour
- The most sensitive layers contain clay loam or peat consolidation occurs mostly in the underlying and overlying layers that are oftenless permeable and more compressible than the aquifer itself Subsidence is a delayed process occurring as far as the pore pressurevariation propagates slowly in the low permeability (aquitard) layers
- The last 30 years PS-InSAR data measures the subsidence or uplift over large-scale areas that we compare with hydrogeologicalgroundwater and geomechanical models and other geodetic techniques (GPSGNSS stations absolute gravimetry)
- Targets he deep aquifer system of western Flanders the Tertiary aquifer system in Central Flanders the Antwerp area the Leuvenarea and the Brussels Region
- The vertical land movements will be compared with 1D geomechanical model results The latter will be performed using geotechnicaleffective stresses as deduced from the pore pressure distribution from the 3D hydrogeological models (Dassargues et al 1989Dassargues 2018)
Land Subsidence Simulation in Merchtem and the SW part of Flanders Groundwater Modelling in Leuven Area
In Antwerp four subsidence processes may occur1 Natural compaction of recent Holocene Formation2 Additional settlement of recent Holocene due tobackfill overburden along the new docks
3 Saturated-unsaturated consolidation of the backfillmaterial itself
4 Compaction of the most compressible layersprobably in the Boom Formation (Paleocene) and inthe Asse clay of the Maldegem Formation (Eocene)due to pore pressure decrease caused bygroundwater pumping in the different Cenozoicaquifers
Using the Robust Network Imaging technique proposed by Kreemer et al (2020) we imaged the VLM resulting from GNSS and PS-InSARon a 001deg x 001deg grid Because PS-InSAR can present large-scale artifacts we filtered out the short-wavelength deformation from PS-InSAR using a median filter with a 25 km radius and combined it with large wavelength deformation retrieved by GNSS (Figure 8) Thisallows quantifying both the large-scale pattern (ie Eifel uplift and coastal subsidence) along with the local deformation
Land subsidence is calculated by accumulating the compaction of all layers The MODFLOW simulator was usedas groundwater flow model and the lsquoSubsidence and Aquifer-System Compactionrsquo (SUB) Package was selectedfor computation of the layer compaction amp subsidence
Subsidence in Antwerp area
Large-Scale Map of Subsidence over Belgium using PS-InSAR and Robust Network Imaging
Abstract
In Belgium most of the identified
subsidence areas could be related to
piezometric fluctuations in aquifers
Using PS-InSAR data two areas of
significant subsidence are observed in
the north of Leuven In these specific
locations many historical and
currently active pumping wells are
present The most important pumping
wells are screened in the Brussels
Formation
Figure 2 Calculated land subsidence (in mm) in the year 2000 caused by the exploitation of the deep aquifer system (Paleozoic basement and Landenian aquifers)
Figure 3 Calculated land subsidence (in mm) in the region around Merchtem and Steenokkerzeel due to
pumping in the Ledo-Paniselian and Ypresian aquifer systems (situation after 10 years of
pumping at the recent pumping rates)
- at least two different zones with dissimilarbehaviours city centre and harbour of Antwerp
- differences in land subsidence rates in differentzones of the area are linked to dissimilarity in the
stability of subsoil
- effect of pumping groundwater from deeper layersparticularly Oligocene aquifer which can play animportant role in the displacements of the region
(Figure 4 and 5)- groundwater model + 1D geomechanical model willbring comprehensive knowledge related to the
subsidence processes going on in the area
12000000
14500000
17000000
19500000
22000000
24500000
aoucirct-87 janv-93 juil-98 janv-04 juil-09 deacutec-14 juin-20
Vo
lum
e (m
3 ye
ar)
Date (month-year)
Volume of groundwater pumped from the Brusselian aquifer (1990-2020)
Figure 6 Evolution of the volume of groundwater pumped from the Brusselian aquifer in the delimited study area around Leuven Belgium
Figure 7 Computed piezometric map in the Brusselianaquifer In background observed piezometric map (VMM
2016) Control points with a 5 meter error gauge related to the calculated piezometric head compared to the
piezometric map
Figure 4 Distribution map of pumping wells over the study area
Figure 5 Drawdown contour map in Oligocene Aquifer during the period 2009-2017
Figure 8 Vertical land motions in Belgium resulting from the combination of PS-InSAR and GNSS data GNSS position time series from Nevada Geodetic Laboratory SAR data ENVISAT date
Toward Next Steps
The following steps will be accomplished through future steps
1 Using high resolution TerraSAR-X radar dataset to have more accurate mapping of ground displacement2 A 3D groundwater multi-layer model simulating water level under transient state along with a 1D geomechanical model simulating
subsidence in those layers will be developed for each target area3 Combining all measurements observed by the Global Navigation Satellite System (GNSS) statistic network over Belgium belonging to
Nevada Geodetic Laboratory (NGL) with repeated absolute gravity measurements and PS-InSAR measurements to either validate PS-InSAR data or retrieve displacement measurements in those areas where no PS points are observed by the radar sensor
4 Comparison of results from different techniques to better interpret the causes and effects of ground deformations5 Future measurements of land surface displacements will be achived by installing different sets of devices called corner reflectors
equipped with professional GNSS stations Corner reflectors will be illuminated by radar satellite as PSrsquos and their displacementsvalues will be verified by the GNSS observations attached to them
In the SW of Flanders between 1920 amp2005 an intensive exploitation of the deepaquifer system (DAS) in the Paleozoicbasement and Landenian Formation hascreated a regional scale depression cone inthe piezometric levels with maximumdrawdowns up to 150 m in the basementaquifer and ~100 m in the LandenianFormation Since 2005 pumping has beenrestricted but recovery goes very slowbecause of the limited recharge of thesedeep layers and even recently theremaining depressions cones are verydeep Simulating of the exploitationhistory of the DAS and calculatingcompaction and subsidence shows thatsubsidence reaches up to 3 cm in a 50 km-wide EW oriented strip (Figure 2)
In the Flemish-Brabant province around Merchtemand Steenokkerzeel known for its breweriesgroundwater exploitation in the Ledo-Paniselian andYpresian aquifers but the depression that comes inthese layers are local and limited only a few metersdeep This is insufficient to create significantsubsidence even after a decade of pumping as themodel shows (Figure 3) Land subsidence is less thana cm
A 3D groundwater flow model integrating the
different geological formations the hydrogeological
parameters the stress factors (see Figure 6) and
historical data for the area of Leuven has been
developed The model has been calibrated in steady
state (Figure 7) The model will be now calibrated in
transient conditions and then be coupled with a-
geomechanical model for consolidation and rebound
calculation
Combining both GNSS and PS-InSARdata to reconstruct vertical landmotions over Belgium- GNSS observations allow computinggeocentric velocities of a network ofGNSS stations separated by a fewtens of kilometers
- PS-InSAR data allows deriving thedeformation field with a much higherresolution but relative to anarbitrary local reference
Contact point Coordinator of the Brain-Belspo funded LASUGEO project xdevleeschouwernaturalsciencesbe and twitter account LASUGEO1
Figure 1 Sentinel1-A ascending LOS velocities across part of Belgium showing two main subsidence bowls (in the Merchtem and Antwerp areas)
