In this work, we present the results of study of physicochemical parameters of sediments from the retaining Sidi Chahed dam, and the use of GIS to achieve a relationship between the geological nature of the watershed and sediments of this retaining of dam from ASTER image. The physicochemical characterization of the sediments was make in order to determine the main factors that govern the exchanges of various forms of phosphorus at the water-sediment interface, and of determining the geological nature of the land crossed by the tributary waters feeding the dam retaining.
The results obtained showed that the average values of carbonates of calcium and pH, which are respectively 36% and 8.3, are more important. The comparison of the geological map and the hydrographic network map shows that the majority of grounds crossed by the tributary waters feeding retaining of dam are the marl and limestone of Miocene, which increases the percentage of calcium carbonate in the sediments of the retaining of dam and therefore favors the dominance of fraction of phosphorus CaCO3 -P (76%) in sediments.