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Ground water management and its consequences in Delft, the Netherlands as observed by Persistent Scatterer Interferometry

Freek J. van Leijen(1) and Ramon F. Hanssen(1)

(1) Delft University of Technology, Kluyverweg 1, 2629 HS Delft, Netherlands

Abstract

Infrastructure in Delft, the Netherlands, is threatened by ground water. As large parts of the country, Delft is situated below mean sea level and maintenance of ground water levels is therefore of high importance. Subsidence in combination with ground water level rise has resulted in severe problems, especially in the last 20 years. Currently, the difference between ground level and mean ground water level is at certain locations only 50-60 cm, with even lower margins during periods of heavy rain. Especially buildings in the historical city center which are often founded on wooden poles are vulnerable for these relative high ground water levels.

Apart from natural causes, artificially induced subsidence and ground water level fluctuations deteriorate the situation. Industrial activities in Delft have been withdrawing ground water since 1916. The amount of extraction has changed over time and has a seasonal cycle. The withdrawal causes subsidence and has direct and indirect effects on the relative ground water level. Lately, due to changes in the production process, the use of ground water has become unnecessary. As instant termination of the extraction process would have a severe impact on the already sensitive ground water situation, a gradual decrease of the extraction volume is proposed. However, because of the unique soil decomposition in the Dutch coastal area (sand, clay, peat), even the effects of a gradual decrease can not be predicted very well. A more profound understanding of the relation between ground water extraction, subsidence (or uplift) and ground water level is therefore necessary.

In this contribution Persistent Scatterer Interferometry (PSI) results of the city of Delft are used to deduct a relation between ground water extraction and subsidence. Time series of the extraction volume are related to the PSI results. Furthermore, since 2000 the ground water levels at 150 locations are measured automatically on an hourly basis, providing a unique opportunity to relate subsidence with the actual ground water level. The PSI results are validated using leveling data. Using ERS1/2 as well as Envisat data, the full period between 1992 to 2007 is analyzed.

 

Workshop presentation

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry