Study of groundwater properties and behaviour using geospatial techniques

Groundwater contributes a significant proportion of the earth’s freshwater and is essential to sustain life on earth, but its availability in spatial and temporal dimensions is not uniform. With the advent of efficient pumps and rural electrification, global groundwater extraction increased from 312 km3/year in the 1960s to 800 km3/year in 2000s; approximately 70% of this extraction is used for agriculture. About half of domestic human water consumption in urban areas is from groundwater. The ever-increasing dependence on groundwater has led to its depletion across various parts of the world. This trend must be reversed to sustain the critical role of groundwater. Groundwater monitoring based on validated data can provide information that can guide decision making to decrease groundwater stress on local and global scales. This thesis aims to monitor spatio-temporal changes in groundwater and related phenomena (like land subsidence) using geospatial techniques like InSAR, GRACE, GIS, data analysis and data visualisation. The over-extraction or rebound of groundwater can lead to land deformation because of the change in effective stress of underground sediments. Groundwater-induced land movement can cause damage to property and resources, and hence it must be monitored for the safety and economics of a city. This thesis explores the suitability of Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) to measure land deformation and different senor-software for InSAR processing. The groundwater quantity variation and resulting land deformation for London using InSAR and Gravity Recovery and Climate Experiment (GRACE) between 2002-2010 were analysed. Long-term, decreasing, complex, non-linear patterns in the spatial and temporal domains from both InSAR and GRACE datasets were observed. The land movement velocities varied from -6 to +6 mm/year, and their reliability was validated with observed GNSS data by conducting a two-sample t-test. The average groundwater loss estimated from GRACE was found to be 9.003 MCM/year. The results demonstrate that InSAR and GRACE complement each other and can be an excellent source of monitoring groundwater for hydrologists. Then groundwater induced subsidence for London and the National Capital Territory of Delhi (NCT-Delhi) between 2016 and 2020 were studied. The land movement velocities were found to vary between -24 mm/year to +24 mm/year for London and between -18 mm/year to +30 mm/year for NCT-Delhi. This land movement was compared with observed groundwater levels and spatio-temporal variation of groundwater. A 1-D mathematical model was used to quantify land deformation for a given change in groundwater level. It was broadly observed that when large volumes of groundwater are extracted, it leads to land subsidence, and when groundwater is recharged, surface uplift is witnessed. However the local geology, did play an important role in the extent of subsidence, which was considered in the mathematical model. The increased pressure on groundwater can cause spatio-temporal changes in its quality because of various atmospheric stimulations, varied geology, variation in subsurface mineralogy and factors controlling residence times. Moreover, the variation of groundwater quality is vital for the sustainable management and safety of groundwater. Thus, the variation in groundwater quality is analysed from observed data for London between 2000 and 2020. The data samples were used from 500 wells in the London basin, and the data is provided in the free open access domain by Environment Agency. The overall groundwater in London was found to be dominant magnesium bicarbonate type which typically represents shallow fresh groundwater, and spatio-temporal variations of hardness, sodium, and dissolved oxygen (DO) were also studied. Significant variations in the range of each constituent were found, which was attributed to variation in the geology of the London Palaeogene aquifers and anthropogenic activities. All the case studies help better understand the phenomenon of spatio-temporal variation in groundwater behaviour and associated land deformation for urban cities. The research presented in this thesis can be used to determine whether groundwater is available and suitable for its intended purpose, discover pollutants, examine any spatio-temporal variations, and monitor land subsidence

Comparative Study of Groundwater-Induced Subsidence for London and Delhi Using PSInSAR

Groundwater variation can cause land-surface movement, which in turn can cause significant and recurrent harm to infrastructure and the water storage capacity of aquifers. The capital cities in the England (London) and India (Delhi) are witnessing an ever-increasing population that has resulted in excess pressure on groundwater resources. Thus, monitoring groundwater-induced land movement in both these cities is very important in terms of understanding the risk posed to assets. Here, Sentinel-1 C-band radar images and the persistent scatterer interferometric synthetic aperture radar (PSInSAR) methodology are used to study land movement for London and National Capital Territory (NCT)-Delhi from October 2016 to December 2020. The land movement velocities were found to vary between −24 and +24 mm/year for London and between −18 and +30 mm/year for NCT-Delhi. This land movement was compared with observed groundwater levels, and spatio-temporal variation of groundwater and land movement was studied in conjunction. It was broadly observed that the extraction of a large quantity of groundwater leads to land subsidence, whereas groundwater recharge leads to uplift. A mathematical model was used to quantify land subsid-ence/uplift which occurred due to groundwater depletion/rebound. This is the first study that compares C-band PSInSAR-derived land subsidence response to observed groundwater change for Lon-don and NCT-Delhi during this time-period. The results of this study could be helpful to examine the potential implications of ground-level movement on the resource management, safety, and economics of both these cities

Applications of SAR Interferometry in Earth and Environmental Science Research

This paper provides a review of the progress in regard to the InSAR remote sensing technique and its applications in earth and environmental sciences, especially in the past decade. Basic principles, factors, limits, InSAR sensors, available software packages for the generation of InSAR interferograms were summarized to support future applications. Emphasis was placed on the applications of InSAR in seismology, volcanology, land subsidence/uplift, landslide, glaciology, hydrology, and forestry sciences. It ends with a discussion of future research directions

Radar interferometry techniques for the study of ground subsidence phenomena: a review of practical issues through cases in Spain

Subsidence related to multiple natural and human-induced processes affects an increasing number of areas worldwide. Although this phenomenon may involve surface deformation with 3D displacement components, negative vertical movement, either progressive or episodic, tends to dominate. Over the last decades, differential SAR interferometry (DInSAR) has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas. This work discusses the main advantages and limitations of addressing active subsidence phenomena by means of DInSAR techniques from an end-user point of view. Special attention is paid to the spatial and temporal resolution, the precision of the measurements, and the usefulness of the data. The presented analysis is focused on DInSAR results exploitation of various ground subsidence phenomena (groundwater withdrawal, soil compaction, mining subsidence, evaporite dissolution subsidence, and volcanic deformation) with different displacement patterns in a selection of subsidence areas in Spain. Finally, a cost comparative study is performed for the different techniques applied.The different research areas included in this paper has been supported by the projects: CGL2005-05500-C02, CGL2008-06426-C01-01/BTE, AYA2 010-17448, IPT-2011-1234-310000, TEC-2008-06764, ACOMP/2010/082, AGL2009-08931/AGR, 2012GA-LC-036, 2003-03-4.3-I-014, CGL2006-05415, BEST-2011/225, CGL2010-16775, TEC2011-28201, 2012GA-LC-021 and the Banting Postdoctoral Fellowship to PJG

From site-scale to large areas monitoring of ground deformation phenomena by integration of different DInSAR techniques in Crotone Province (Southern Italy)

One of the most significant aims of this research project has been to apply SAR methods for the monitoring, the investigation and the evaluation of ground deformation phenomena in the Crotone province (Southern Italy). In detail, landslides and subsidence are the most remarkable and dangerous natural hazards in the study area, affecting people, buildings and main infrastructures. The intention was to show the potential of Differential Interferometry SAR (DInSAR) techniques for the detection and the estimation of the velocities and of the deformation of surface displacements, both on very local scale (slope scale) and on wide areas (kilometre-size extension). Such aim is achievable through the integration of DInSAR techniques along with conventional monitoring tools. The general idea of the project has been to assess the landslide hazard in selected areas of the Crotone province and to update the related landslide inventory map of the area, dated back to 2006, by means of DInSAR techniques. These goals have been reached through the comprehension and the understanding of the movements, on one hand on a very local scale (slope), and on the other hand, on a wide-area scale (the whole Crotone province). Additionally, two other case studies of subsidence, originated by different sources, have been studied with interferometry techniques, showing the suitability of such methods for other types of ground deformation. Several Multi Temporal Interferometry (MTI, Wasowski & Bovenga, 2014) approaches have been here applied, in order to investigate and analyze displacements present in the area, and the integration with “conventional” methods, such as inclinometers, piezometers and geomorphological surveys, turned out to be relevant for these purposes, providing very precise information about the nature and causes of ground deformation

Radar Interferometry for Monitoring Crustal Deformation. Geodetic Applications in Greece

The chapatti and breadmaking quality of nine (eight Indian and one Australian) wheat (Triticum aestivum L.) cultivars was compared. The extension of a chapatti strip measured with a Kieffer dough extensibility rig correlated with chapatti scores for overall quality (r = 0.84), pliability (r = 0.91), hand feel (r = 0.72), chapatti eating quality (r = 0.68), and taste (r = 0.80). Overall chapatti quality also correlated with the resistance to extension of a chapatti strip (r = 0.68) when tested for uniaxial extension with a texture analyzer. The texture analyzer provided objectivity in the scoring of chapatti quality. The high-molecular-weight glutenin subunit protein composition assessed by sodium dodecyl sulfate polyacrylamide gel electrophoresis did not correlate with the overall chapatti score. A negative correlation was found between chapatti and bread scores (r = 0.77). The different requirements for chapatti and bread quality complicate the breeding of new wheat varieties and the exchange of germplasm between regions producing wheat for chapatti and those supplying bread producers

Electromagnetic modeling for SAR polarimetry and interferometry

Investigation of the globe remotely from hundreds of kilometers altitude, and fast growing of environmental and civil problems, triggered the necessity of development of new and more advanced techniques. Electromagnetic modeling of polarimetry and interferometry has always been a key driver in remote sensing research, ever since of the First pioneering sensors were launched. Polarimetric and interferometric SAR (Synthetic Aperture Radar) surveillance and mapping of the Earth surface has been attracting lots of interest since 1970s. This thesis covers two SAR's main techniques: (1) space-borne Interferometric Synthetic Aperture Radar (InSAR), which has been used to measure the Earth's surface deformation widely, and (2) SAR Polarimetry, which has been used to retrieve soil and vegetation physical parameters in wide areas. Time-series InSAR methodologies such as PSI (Permanent Scatterer Interferometry) are designed to estimate the temporal characteristics of the Earth's deformation rates from multiple InSAR images acquired over time. These techniques also enable us to overcome the limitations that conventional InSAR suffer, with a very high accuracy and precision. In this thesis, InSAR time-series analysis and modeling basis, as well as a case study in the Campania region (Italy), have been addressed. The Campania region is characterized by intense urbanization, active volcanoes, complicated fault systems, landslides, subsidence, and hydrological instability; therefore, the stability of public transportation structures is highly concerned. Here Differential Interferometric Synthetic Aperture Radar (DInSAR), and PSI techniques have been applied to a stack of 25 X-band radar images of Cosmo-SkyMed (CSK) satellites collected over an area in Campania (Italy), in order to monitor the railways' stability. The study area was already under investigation with older, low-resolution sensors like ERS1&2 and ENVISAT-ASAR before, but the number of obtained persistent scatterers (PSs) was too limited to get useful results. With regard to SAR polarimetry, in this thesis a fully polarimetirc SAR simulator has been presented, which is based on the use of sound direct electromagnetic models and it is able to provide as output the simulated raw data of all the three polarization channels in such a way as to obtain the correct covariance or coherence matrixes on the final focused polarimetic radar images. A fast Fourier-domain approach is used for the generation of raw signals. Presentation of theory is supplemented by meaningful experimental results, including a comparison of simulations with real polarimetric scattering data

Urban Deformation Monitoring using Persistent Scatterer Interferometry and SAR tomography

This book focuses on remote sensing for urban deformation monitoring. In particular, it highlights how deformation monitoring in urban areas can be carried out using Persistent Scatterer Interferometry (PSI) and Synthetic Aperture Radar (SAR) Tomography (TomoSAR). Several contributions show the capabilities of Interferometric SAR (InSAR) and PSI techniques for urban deformation monitoring. Some of them show the advantages of TomoSAR in un-mixing multiple scatterers for urban mapping and monitoring. This book is dedicated to the technical and scientific community interested in urban applications. It is useful for choosing the appropriate technique and gaining an assessment of the expected performance. The book will also be useful to researchers, as it provides information on the state-of-the-art and new trends in this fiel