Abstract
The Donga Department is located in the northwest of Benin in an area made up of crystalline and crystallophyllic basement rocks where most of the groundwater resources are found in the area of weathered and conductive fractures. The carrying out of drilling campaigns in this department are often crowned with a significant number of negative boreholes (<0.7m3 /h) due to the poor choice of sites for drilling. This leads to situations of difficulties in supplying drinking water, or even more frequent shortages during the dry season. The objective of this study is to use geophysical methods characterize the fractured basement areas, with a view to improving the implantations and the sustainable management of the aquifers they contain. The application of the Protonic Magnetic Resonance (PMR) method made it possible to determine the hydrogeological properties of the fracture zones. As a result, the determination of the hydrodynamic properties shows that the WPMR, T2* and Sy values in 5 different localities of the study area are between 4 and 13% respectively, between 150 and 212.5 ms and between 2.3 and 8.2%. The minimum height of the water slide is 820 mm and the maximum height is estimated at 3672 mm for a water reserve of up to 2313 mm in the Donga gneisses. It emerges from this study that in the department of Donga the PMR water content is also a function of the particle size. T2* of the fractured zone.
Highlights
In the middle of the basement rocks, discontinuous aquifers are affected by tectonic dislocations which generate zones of fractures and weathered layers
These results reveal that the Protonic Magnetic Resonance (PMR) water content (WPMR) in the department of Donga varies according to the investigated sites and the geological formations in place
The calculation of the PMR water column indicates that the gneisses of Donga have the highest water column (3672 mm) and the granitoid migmatites have the highest WPMR with 13%
Summary
In the middle of the basement rocks, discontinuous aquifers are affected by tectonic dislocations which generate zones of fractures and weathered layers. The work of [2], [3], [4] under the same conditions in West Africa, [5], [6] in Greece and [7], [8] in India have proposed a hydrogeological prospecting approach This approach makes it possible to combine geology, hydrogeology and geophysics on the one hand.
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