TY  - JOUR
A1  - Ronczka, Mathias
A1  - Günther, Thomas
A1  - Grinat, Michael
A1  - Wiederhold, Helga
T1  - Monitoring freshwater–saltwater interfaces with SAMOS – installation effects on data and inversion
Y1  - 2020
VL  - 18
IS  - 4
SP  - 369
EP  - 383
JF  - Near Surface Geophysics
DO  - 10.1002/nsg.12115
DO  - 10.23689/fidgeo-4720
N2  - A major problem for the freshwater supply of coastal regions is the intrusion of saltwater into aquifers. Due to extensive extraction of freshwater to suffice increasing drinking water demands and/or in periods of reduced groundwater recharge, the equilibrium state may be disturbed. The result is an upconing or movement of the fresh–saline groundwater interface, which reduces the local drinking water resources at coastal regions or islands. The saltwater monitoring system (SAMOS) is a vertical electrode chain installed in a backfilled borehole. It provides a solution to observe the transition zone in detail, both temporally and spatially. We present monitoring data of the first year from three locations - with different geological conditions that show disturbances in the resistivity distribution that result from the drilling processes. A clayey backfilling, for example, can lead to beam-like artefacts, and a mixed fluid within the backfilling changes its bulk resistivity, both leading to misinterpretations. We performed data inversion under cylindrically symmetrical conditions in full-space in order to separate these resistivity artefacts from the undisturbed background. Data inversion reveals that it is possible to separate drilling effects on the resistivity distribution from the undisturbed background. Thus, an interpretation of the natural transition zones can be made immediately after the installation.
UR  - http://resolver.sub.uni-goettingen.de/purl?gldocs-11858/9066
ER  -