Chronological reflection on monitoring urban areas subsidence due to groundwater extraction

Land subsidence affects urban areas worldwide. Sometimes it could be driven by intensive groundwater withdrawal to assure different urban needs and functionalities. Some of these urban areas have a long history of subsidence that covers almost a century. The aim of this paper is to present the evolution of several urban areas affected by land subsidence, the methods used to monitor vertical displacements along the decades in relationship to the groundwater extraction associated to the urban expansion, and the mitigation techniques used for countering the effects of intensive groundwater withdrawal. Even the originally applied subsidence monitoring methods (such as geometric levelling) are still very sensitive, in terms of time consuming, covered area, and financial effort, these methods might be complemented by new methods based on Synthetic Aperture Radar Interferometry (InSAR). InSAR methods show also a significant progress during the last decades when considering the subsidence sensed order of magnitude

Advances in groundwater protection strategy using vulnerability mapping and hydrogeological GIS databases

Groundwater vulnerability maps are useful for environmental planning and decision-making. They are usually produced by applying vulnerability assessment methods using overlay and index techniques. On the basis of a review of the vulnerability assessment and mapping methods, new research challenges in aquifers vulnerability assessment are identified.Operations like the parameter quantification, the vulnerability index computing, and the final classification, are affected by an empirical character which of course affects also the final product: the vulnerability map. In consequence, the validity of the resulted vulnerability maps must be evaluated in function of the objectives of the survey and in function of the specific characteristics of each studied zone. Analysing their uncertainty can represent the base for their validation. Uncertainty can be investigated through sensitivity analysis or through comparisons between vulnerability maps created using different methods. Both these strategies are developed in this study and illustrated from applications on practical case studies of vulnerability mapping.Applying the EPIK parametric method, a vulnerability assessment has been made for a small karstic groundwater system in southern Belgium. The aquifer consists in a karstified limestone of Devonian age. A map of intrinsic vulnerability of the aquifer shows three vulnerability areas. A parameter-balance study and a sensitivity analysis were performed to evaluate the influence of single parameters on aquifer vulnerability assessment using the EPIK method. This approach provides a methodology for the evaluation of vulnerability mapping and for more reliable interpretation of vulnerability indices for karst groundwater resources.Five different methods for assessing the intrinsic vulnerability were tested on a case study for comparison of their results. The test area consists in a slightly karsified basin located in the Condroz region (Belgium). The basin covers about 65 km² and the karstic aquifer provides a daily water supply of about 28000 m³ in drainage galleries. Several campaigns of measurements consisting in morpho-structural observations, shallow geophysics, pumping and tracer tests have provided useful data. The tested methods were: EPIK (Doerfliger and Zwahlen, 1997), DRASTIC (Aller et al., 1987), ‘German methods’ (von Hoyer & Söfner, 1998), GOD (Foster, 1987), and ISIS (Civita and De Regibus, 1995). DRASTIC and GOD represent classic approaches in vulnerability assessment. ISIS is a development based on DRASTIC, SINTACS (Civita, 1994), and GOD methods, where more importance is given to the recharge.EPIK was developed specifically for karstic geological contexts and the ‘German methods’ was developed in Germany for a broad range of geological contexts. Compared results are shown and commented. It seems that despite the fact that the EPIK method can better outline the karstic features about 92% of the studied area is assessed by this technique as low vulnerable. In contrast, the other four methods are considering extended zones of high or moderate vulnerability. From the analysis, it seems also that reducing the number of considered parameters is not ideal when adaptation to various geological contexts is needed.Reliability and validity of groundwater analysis strongly depend on the availability of large volumes of high quality data. Putting all data in a coherent and logical structure supported by a computing environment helps ensure a validity and availability, and provides a powerful tool for hydrogeological studies. A hydrogeological GIS database that offers facilities for groundwater vulnerability analysis and hydrogeological modelling has been designed in Belgium, for the Walloon Region. Data from five river basins, chosen for their contrasted applications that have been developed allow now further advances. However the basic concept of the database is represented by the commonly accepted ‘Georelational model’ developed in the 1970s, the database concept presents a distinctive character.There is a growing interest in the potential for integrating GIS technology and groundwater simulation models. Between the mentioned spatial database schema and the groundwater numerical model interface GMS (Groundwater Modelling System) a ‘loose-coupling’ tool was created. Following time and spatial queries, the hydrogeological data stored in the database can be easily used within different groundwater numerical models. This development can represent also a solid base for the physical processes integration within the quantification of the vulnerability methods parameters.The fundamental aim of this work was to help improving the aquifers protection strategy using vulnerability mapping and GIS. The results are offering the theoretical and practical basis for developing a strategy for protecting the groundwater resources

Urban Hydrogeology Studies

Urbanization is a pervasive phenomenon of our time, and sustainable urban development is one of the greatest challenges faced by the contemporary world [...

Sensitivity Analysis for the Epik Method of Vulnerability Assessment in a Small Karstic Aquifer, Southern Belgium

Applying the EPIK parametric method, a vulnerability assessment has been made for a small karstic groundwater system in southern Belgium. The aquifer is a karstified limestone of Devonian age. A map of intrinsic vulnerability of the aquifer and of the local water-supply system shows three vulnerability areas. A parameter-balance study and a sensitivity analysis were performed to evaluate the influence of single parameters on aquifer-vulnerability assessment using the EPIK method. This approach provides a methodology for the evaluation of vulnerability mapping and for more reliable interpretation of vulnerability indices for karst groundwater resources

Chronological reflection on monitoring urban areas subsidence due to groundwater extraction

Land subsidence affects urban areas worldwide. Sometimes it could be driven by intensive groundwater withdrawal to assure different urban needs and functionalities. Some of these urban areas have a long history of subsidence that covers almost a century. The aim of this paper is to present the evolution of several urban areas affected by land subsidence, the methods used to monitor vertical displacements along the decades in relationship to the groundwater extraction associated to the urban expansion, and the mitigation techniques used for countering the effects of intensive groundwater withdrawal. Even the originally applied subsidence monitoring methods (such as geometric levelling) are still very sensitive, in terms of time consuming, covered area, and financial effort, these methods might be complemented by new methods based on Synthetic Aperture Radar Interferometry (InSAR). InSAR methods show also a significant progress during the last decades when considering the subsidence sensed order of magnitude

Sensitivity analysis for the EPIK vulnerability assessment in a local karstic aquifer

Applying the EPIK parametric method, a vulnerability assessment has been made for a small karstic groundwater system in southern Belgium. The aquifer is a karstified limestone of Devonian age. A map of intrinsic vulnerability of the aquifer and of the local water-supply system shows three vulnerability areas. A parameter-balance study and a sensitivity analysis were performed to evaluate the influence of single parameters on aquifer-vulnerability assessment using the EPIK method. This approach provides a methodology for the evaluation of vulnerability mapping and for more reliable interpretation of vulnerability indices for karst groundwater resources

Current trends in the management of groundwater specific geospatial information

The purpose of this paper is to present the state-of-art of groundwater geospatial information management, highlighting the relevant data model characteristics and technical implementation of the European Directive 2007/2/EC, also known as the INSPIRE Directive. The maturity of the groundwater geodata management systems is of crucial importance for any kind of activity, be it a research project or an operational service of monitoring, protection or exploitation activities. An ineffective and inadequate geodata management system can significantly increase costs or even overthrow the entire activity ([1-3]). Furthermore, following the technological advancement and the extended scientific and operational interdisciplinary connectivity at national and international scale, the interoperability characteristics are becoming increasingly important in the development of groundwater geospatial information management. From paper recordings to digital spreadsheets, from relational database to standardized data models, the manner in which the groundwater data was gathered, stored, processed and visualized has changed significantly over time. Aside from the clear technical progress, the design that captures the natural connections and dependencies between each groundwater feature and phenomena have also evolved. The second part of our paper address the variations that occurred when outlining the different groundwater geospatial information management models, differences that depict the complexity of hydrogeological data

Conceptual model of hydrogeological information for a GIS-based decision support system of artificial recharge in semi-arid regions

FP6 STREP GABARDINE (Project Nb. 518118-1