ln the Senegal middle valley, the salt distribution is not related to the present faint topography. This lack of logic is one of the major constraints for establishment of new irrigated areas. The salt distribulion is here studied to better understand its variability, and to describe its structure and spatial arrangement. Saline areas are delineated measuring the electromagnetic soil conduclivity (EM). The kriged map is compared to the aerial photograph. The salinity is distributed as stripes in the SW-NE direclion, fringing a former creek on the southem bank. The stripe is intersected by an actual creek bed, indicating that the salt distribution is ancienl and does not result from a recent remobilization of the marine salt incorporated in the soil. The relalionship between salt distribution and the former geomorphology allows us to survey the whole N'Galenka region using the EM measuremenls on selected transects.