|Paper title||Detection of land subsidence in the city of Recife/Brazil induced by groundwater withdrawal using SAR interferometry|
|Form of presentation||Poster|
Water scarcity is a constant concern for millions of people around the world without access to clean water. This reality is also verified in the city of Recife, located in the northeast of Brazil. The municipality is built on an estuarine plain composed of several rivers (Capibaribe, Beberibe, Tejipió). Over the past 50 years, population growth combined with periods of surface water crisis have significantly boosted groundwater use. The capture of this resource, however, occurs in an indiscriminate way in a large part of the city. Groundwater management is inefficient. The biggest limitation is evident in the control of wells, which are estimated at more than 13 thousand. Most are illegal and of unknown existence to inspection bodies. Over the decades, the weakness in groundwater management has contributed to the overexploitation of confined aquifers. The excessive removal of water resources from the subsoil has caused a reduction in the piezometric level to values above 100 m in the southern part of Recife, in the densely built-up neighborhood of Boa Viagem. This implies a strong risk of land subsidence. The geological phenomenon causes surface lowering and causes greater concern in urban areas. The deformation of the terrain can generate relevant impacts on infrastructure and the environment, causing economic and social damage, and compromising people's quality of life. In general, several cities around the world live with this situation. In addition to natural causes, the main occurrences result from human action in the accentuated exploitation of aquifers. The aim of this research is to use interferometry synthetic aperture radar (InSAR) to detect land subsidence in the coastal plain of Recife caused by the exploitation of groundwater resources. The use of this technology is seen as an innovation to current recurrent practices, based on terrestrial measurement techniques. The procedure is performed with a persistent scatterer interferometric (PSI), in the analysis of SAR data with a single-look complex (SLC) processing level, formed by satellite images: COSMO-SkyMed (ascending orbit, HH polarization, X-band), Sentinel -1 (descending orbit, VV polarization, C band) and PAZ (ascending and descending orbit, HH polarization, X band). Preliminary results reveal a correlation between land subsidence and reduction of groundwater in the southern zone due to water desaturation in the neighborhood of Boa Viagem, with a velocity close to -3 mm/year. Thus, the wide availability of interferometric data from satellite SAR missions associated with an advanced processing method should provide a better understanding of processes that generate superficial instability – such as the land subsidence. Using InSAR provides opportunities to test hypotheses and investigate situations that were previously unlikely due to the lack of adequate information. Its application opens the way for new perspectives in the study of the compaction of compressible sediments in the Recife coastal plain as a result of the decline in groundwater levels.
Keywords: land subsidence; groundwater; Recife; SAR interferometry