Hydraulic properties at the North Sea island of Borkum derived from joint inversion of magnetic resonance and electrical resistivity soundings

verfasst von

T. Günther, M. Müller-Petke

Abstract

For reliably predicting the impact of climate changes on salt/freshwater systems below barrier islands, a long-term hydraulic modelling is inevitable. As input we need the parameters porosity, salinity and hydraulic conductivity at the catchment scale, preferably non-invasively acquired with geophysical methods. We present a methodology to retrieve the searched parameters and a lithological interpretation by the joint analysis of magnetic resonance soundings (MRS) and vertical electric soundings (VES). Both data sets are jointly inverted for resistivity, water content and decay time using a joint inversion scheme. Coupling is accomplished by common layer thicknesses. We show the results of three soundings measured on the eastern part of the North Sea island of Borkum. Pumping test data is used to calibrate the petrophysical relationship for the local conditions in order to estimate permeability from nuclear magnetic resonance (NMR) data. Salinity is retrieved from water content and resistivity using a modified Archie equation calibrated by local samples. As a result we are able to predict porosity, salinity and hydraulic conductivities of the aquifers, including their uncertainties. The joint inversion significantly improves the reliability of the results. Verification is given by comparison with a borehole. A sounding in the flooding area demonstrates that only the combined inversion provides a correct subsurface model. Thanks to the joint application, we are able to distinguish fluid conductivity from lithology and provide reliable hydraulic parameters as shown by uncertainty analysis. These findings can finally be used to build groundwater flow models for simulating climate changes. This includes the improved geometry and lithological attribution, and also the parameters and their uncertainties.

Externe Organisation(en)

Leibniz-Institut für Angewandte Geophysik (LIAG)

Typ

Artikel

Journal

Hydrology and Earth System Sciences

Band

16

Seiten

3279-3291

Anzahl der Seiten

13

ISSN

1027-5606

Publikationsdatum

2012

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Gewässerkunde und -technologie, Erdkunde und Planetologie (sonstige)

Ziele für nachhaltige Entwicklung

SDG 6 – Sauberes Wasser und sanitäre Einrichtungen, SDG 13 – Klimaschutzmaßnahmen

Elektronische Version(en)

https://doi.org/10.5194/hess-16-3279-2012 (Zugang: Offen)