Community Research and Development Information Service - CORDIS

Mapping freshwater discharge by underwater multi electrode profiling

UNDER WATER MULTI ELECTRODE PROFILING, so called UMEP, was used to produce a map of the underground resistivity at the sea bottom. Seven arrays were used and filtered to reach a data density of around one sounding every 5 metre. First results show apparent resistivities measured for seven depths of investigation levels. Results show that the longer electrode spacing ( 100m) shows resistive anomalies along the coast. The inversion process was a 1D inversion made by an automatic routine.

The water depth and resistivity are known, the number of layers is 3 and the resistivity of the deeper layer is less than 20ohm. It has been shown that the resistivity of the clay as well as the resistivity of the salt-water saturated sand is less than this value. The results can be represented on inversed profiles. The anomalies identified on the apparent resistive profiles are still present on the inversion results and correspond to outflows of fresh water. The results could also be presented in term of depth map of the interface between the resistive ( fresh water saturated sand) and conductive layers ( tertiary clay or salt water saturated sand).

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College Propedeutique
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