■ Colloque GEOFCAN Géophysique des sols et des formations superfic ie lle s 11-12 septembre 1997, Bondy, France BRGM, INRA, ORSTOM, UPMC Abstracts et Résumés étendus 17 I Abstract The numerous hill lakes, recently constructed in central Tunisia, have to prevent the risks of soil erosion. The knowledge of soil distribution in the watershed is required to optimize the implementation of anti- erosive devices. Geophysical and pedological prospectings were carried out in the lower part of El Gouazine watershed. Electromagnetic and electrical methods were applied along three toposequences and the variation of resistivities were compared with pedological observations. In spite of scarce geological information, the geophysical approach complete the pedological observations and precise the limits of four soil types. Gérard Bellier 1 , Nourredine Gaaloul 2 , Jean-Olivier Job 3 , Jean-Pierre Montoroi 1 , Patrick Zante 3 1 ORSTOM, Laboratoire des Formations Superficielles, 32 Avenue Henri Varagnat, 93143 Bondy cedex, France 2 INRGREF, rue Hédi Karray, B.P. 10, 2080 Ariana, Tunisie 3 CENID RASPA/ ORSTOM, Programme de recherche sur la dynamique des sels dans la Comarca Lagunera, A.P. 225-3, Z.I 35071, Gomez Palacio, Dgo, Mexique 4 ORSTOM, 5 impasse Chahrazed, B.P. 434, 1004 E l Menzah 4, Tunisie nterprétation pédologique de données électromagnétiques et électriques. Application au bassin versant d’E l Gouazine (Tunisie centrale)