Magnetotelluric Method in the Exploration of Deeper Aquifers

Electrical methods are commonly used in groundwater investigations but in case of deeper aquifers the electrical tomography cannot achieve deeper targets and the electrical sounding cannot ensure a complete and dense space coverage. In such a case the use of the magnetotelluric method can provide for great depths of research, as well as a good space sampling. The capabilities of the MT-method are shown in two examples of deeper groundwater investigations carried out in the north-western Croatia. In the Gotalovec area the aquifers are fractured carbonates (Triassic and Miocene) underlying thick series of Neogenic clays and marls. On the basis of all results a conclusion can be drawn that the MT-method should be applied first in similar model in order to define potential aquifers and indicate the most favourable micro-locations where reflection seismics can be applied as the latter allows for a more precise mapping of aquifer depths and faults. The second geological model, investigated in the Apatovac area, is very complex consisting of clastic and magmatite bodies. The MT-method provided for a complete and clear solution to the structural relationships in the area and gave a precise definition of the deep narrow diabase body which is mineral water aquifer.