3D groundwater flow and deformation modelling of Madrid aquifer
R. Boni', C. Meisina, F. Zucca
Department of Earth and Environmental Sciences, University of Pavia, Italy <
P. Teatini, C. Zoccarato, A. Franceschini
Dept. of Civil, Environmental and Architectural Engineering,
University of Padova, Padova, Italy
P. Ezquerro, M. Bejar-Pizarro, J. A. Fernandez-Merodo, C. Guardiola-Albert, G. Herrera
Geohazards InSAR Laboratory and Modeling Group, Instituto Geologico y Minero de Espana,
Madrid, Spain
J. L. Pastor, R. Tomas
Universidad de Alicante, Dpto. de Ingenieria Civil, Alicante, Spain
A novel methodological approach to calibrate and validate three-dimensional (3D) finite element (FE)
groundwater flow and geomechanical models has been implemented using Advanced Differential Interferometric
SAR (A-DInSAR) data. In particular, we show how A-DInSAR data can be effectively used to (1) constrain the
model set-up in evaluating the areal influence of the wellfield and (2) characterise the aquifer system, specifically
the storage coefficient values, which represents a fundamental step in managing groundwater resources.
The procedure has been tested to reconstruct the surface vertical and horizontal movements caused by the
Manzanares-Jarama wellfield located northwest of Madrid (Spain). The wellfield was used to supply freshwater
during major droughts over the period between 1994 and 2010. Previous A-DInSAR outcomes obtained by ER-1/2
and ENVISAT acquisitions clearly revealed the seasonality of the land displacements associated to the
withdrawal and recovery cycles that characterized the wellfield development. A time-lag of about one month,
which is in the order of the time span between two SAR acquisitions, between the hydraulic head changes and
the displacements has been detected in this site by a wavelet analysis of A-DInSAR and piezometer time series.
The negligible delay between the forcing factor and the system response and the complete subsidence recovery
when piezometric head recovers supported the understanding of a minor role played by the pore pressure
propagation within clay layers and the almost perfectly elastic behavior of the system (viscosity is negligible),
respectively. The developed geomechanical model satisfactorily reproduces the pumping-induced deformations
with a Root Mean Square Error (RMSE) between observed and simulated land displacements in the order of
0.1-0.3 mm. The results give insights about the approach benefits in deeply understanding the spatio-temporal
aquifer-system response to the management of this strategic water resource for Madrid.
