Satellite Interferometric Investigations of Subsidence Events Associated with Groundwater Extraction in Sao Paulo, Brazil

Authors: B. Mendonça, D. Sandwell

Abstract:

The Metropolitan Region of Sao Paulo (MRSP) has suffered from serious water scarcity. Consequently, the most convenient solution has been building wells to extract groundwater from local aquifers. However, it requires constant vigilance to prevent over extraction and future events that can pose serious threat to the population, such as subsidence. Radar imaging techniques (InSAR) have allowed continuous investigation of such phenomena. The analysis of data in the present study consists of 23 SAR images dated from October 2007 to March 2011, obtained by the ALOS-1 spacecraft. Data processing was made with the software GMTSAR, by using the InSAR technique to create pairs of interferograms with ground displacement during different time spans. First results show a correlation between the location of 102 wells registered in 2009 and signals of ground displacement equal or lower than -90 millimeters (mm) in the region. The longest time span interferogram obtained dates from October 2007 to March 2010. As a result, from that interferogram, it was possible to detect the average velocity of displacement in millimeters per year (mm/y), and which areas strong signals have persisted in the MRSP. Four specific areas with signals of subsidence of 28 mm/y to 40 mm/y were chosen to investigate the phenomenon: Guarulhos (Sao Paulo International Airport), the Greater Sao Paulo, Itaquera and Sao Caetano do Sul. The coverage area of the signals was between 0.6 km and 1.65 km of length. All areas are located above a sedimentary type of aquifer. Itaquera and Sao Caetano do Sul showed signals varying from 28 mm/y to 32 mm/y. On the other hand, the places most likely to be suffering from stronger subsidence are the ones in the Greater Sao Paulo and Guarulhos, right beside the International Airport of Sao Paulo. The rate of displacement observed in both regions goes from 35 mm/y to 40 mm/y. Previous investigations of the water use at the International Airport highlight the risks of excessive water extraction that was being done through 9 deep wells. Therefore, it is affirmed that subsidence events are likely to occur and to cause serious damage in the area. This study could show a situation that has not been explored with proper importance in the city, given its social and economic consequences. Since the data were only available until 2011, the question that remains is if the situation still persists. It could be reaffirmed, however, a scenario of risk at the International Airport of Sao Paulo that needs further investigation.

Keywords: Ground subsidence, interferometric satellite aperture radar (InSAR), metropolitan region of Sao Paulo, water extraction.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1339035

References:

[1] E. P. Maretti, “Subsidiência de solo deflagrada por intervenções antrópicas: estudo de caso em área situada na porção nordeste da cidade universitária, Butantã, São Paulo (Unpublished Work style),” unpublished.
[2] F. Mingnorance, “Manifestaciones de subsidencia superficial en el Pastal, Norte de Mendoza, Argentina.”, in Revista de la Facultad de Ingeniería, vol. 41, pp. 5-16, 2000.
[3] Secretaria de Saneamento e Recursos Hídricos, “Relatório de situação dos recursos hídricos do Estado de São Paulo (Unpublished Work style),” unpublished.
[4] A. Ming, A. Seki, E. Cavalcanti, L. Aio, N. Akiko, R. Kutekem, T. Bignardi, “Uso da água subterranean na RMSP (Unpublished work style),” unpublished.
[5] J. P. Dias, M. Babinski, R. Hirata, L. Mancini, M. Rosário, A. E. Azevedo, “Caracterização isotrópica da precipitação da cidade de São Paulo (Brasil) e sua relação com as águas subterrâneas (Published Conference Proceedings style),” in VIII Congresso de Geoquímica dos Países de Língua Portuguesa, Avieiro, 2005, pp.433-446, 2005.
[6] B. P. Conicelli, “Gestão das águas subterrâneas na bacia hidrográfica do Alto Tietê (SP) (Unpublished Work style),” unpublished.
[7] R. Bertolo, R. Hirata, B. P. Conicelli, M. Simonato, A. Pinhatti, A. Fernandes, “A água subterrânea para abastecimento público na Região Metropolitana de São Paulo: é possível utilizá-la em larga escala?” in Revista DAE, vol. 63, pp. 6-17, 2014.
[8] Instituto Brasileiro de Geografia e Estatística (SEADE), “Perfil da Região Metropolitana de São Paulo (Unpublished Work style),” unpublished.
[9] A. Rosenqyist, M. Shimada, N. Ito, M. Watanabe, “ALOS PALSAR: A pathfinder mission for global-scale monitoring of the environment,” in Geoscience and Remote sensing, vol. 45, pp. 3307-3316, 2007.
[10] R. Burgmann, P. A. Rosen, E. J. Fielding, “Synthetic aperture radar interferometry to measure Earth’s surface topography and its deformation,” in Annual Review of Earth and Planetary Sciences, vol. 28-1, pp. 169-209, 2000.
[11] D. Massonnet, M. Rossi, C. Carmona, F. Adragna, G. Peltzer, K. Feigl, T. Rabaute, “The displacement field of the Landers earthquake mapped by radar interferometry,” in Nature, vol. 364, pp. 138-142, 1993.
[12] D. Massonnet, K. Feigl, “Radar interferometry and its application to changes in the Earth’s surface,” in Rev. Geophys., vol. 36, pp. 441-500, 1998.
[13] P. A. Rosen, S. Hensley, I. R. Joughin, F. K. Li, S. N. Madsen, E. Rodriguez, R. M. Goldstein, “Synthetic aperture radar interferometry,” in Proc. IEEE, vol. 88, pp. 333-382, 2000.
[14] K. M. Watson, Y. Bock, D. T. Sandwell, “Satellite interferometric observations of ground displacements associated with seasonal groundwater in the Los Angeles basin,” in Journal of Geophysical Research: Solid Earth (1978-2012), vol. 107, pp. 8-15, 2002.
[15] D. Sandwell, R. Mellors, X. Tong, M. Wei, P. Wessel, “GMTSAR: An InSAR processing system based on Generic Mapping Tolls (Unpublished Work style),” unpublished.
[16] R. P. Romeyn, M. C. Garthwaite, “Broad-scale volcano monitoring in Papua New Guinea using satellite interferometric synthetic aperture radar,” in Geoscience Australia, vol. 49, 2012.
[17] W. C. Sousa Junior, E. Ribeiro, E. Sousa, G. B. Pessoa, F. A. dos Santos, “Diagnóstico do uso da água no Aeroporto Internacional de São Paulo (AISP) através de monitoramento remoto do consumo (Unpublished Work style),” unpublished.