Land deformation monitoring using InSAR
Interforemtric Synthetic Aperure Radar (InSAR) technique is widely used in deformation mapping. InSAR can measure the deformation in sub-cm scale over regular time spans of days. The wide spatial and temporal coverage make it a valuable tool for hydrogeological applications especially in mapping, monitoring and simulating groundwater flow, aquifer-system compaction and land subsidence. Moreover, by coupling groundwater flow and soil compaction models, the deformation information can be used implicitly to simulate future land subsidence for regulating groundwater extraction. My research concentrates on how InSAR observations can contribute in improving groundwater models and my ultimate goal is to estimate pumping using these observations.
Compressibility of confined/unconfined soils
Saturated fine grained soils undergo compaction when they lose water from their pores. This compaction is explained by the stress-strain relationship within the poroelastic medium. In reality, soil compacts in 3D, however horizontal displacement is negligible when compared to vertical. Thus, in practice the vertical stress-strain relationship is coupled to three-dimensional groundwater flow in order to simulate and predict compaction of the aquifer system. If the compaction can be predicted once the groundwater flow model and the elastic-plastic properties of the soil are known, it should be possible to reverse the equation to get information on either groundwater flow or soil properties. Currently, I am working on pre-built Delft groundwater model to see how InSAR deformation observations can be used in groundwater model calibration.
Data assimilation and inverse modeling
Inverse modeling and data assimilation techniques are widely used in parameter estimation related to groundwater studies. Basically, some model parameters, which affect groundwater flow physically (i.e. hydraulic conductivity), are estimated through optimization since it is difficult to measure them directly as they differ with space and time. However, if the observations are insufficient or unreliable the estimated parameters can contain some uncertainty. At this point, InSAR technique has a potential of reducing this uncertainty due to its large spatial and temporal coverage. The deformation information coming from InSAR can be used to complete the lacking information in space and time. I am working on sensitivity of estimating hydraulic head time series by making use of hydraulic head-compaction relationship.
Tüfekçi, N., Schoups, G., Giesen, NC., Leijen, FJ., Hanssen, RF., 2010. An InSAR based methodology for estimating groundwater pumping . RSS-2010 Abstract. Remote Sensing Symposium, Delft-The Netherlands.
Tüfekçi, N., Süzen, ML., Güleç, N., 2010. GIS based geothermal potential assessment: A case study from Western Anatolia, Turkey. Energy, 35(1), pp. 246-261.
Tüfekçi, N., Schoups, G., Giesen, NC., Leijen, FJ., Hanssen, RF., 2009. Quantitative assessment of interrelations between groundwater Dynamics and InSAR-derived land subsidence. Geophysical Research Abstracts, Vol. 11- EGU2009-8282, EGU General Assembly 2009, Vienna-Austria.