Transport of dissolved and suspended solids from three coastal rivers (North Central Algeria)

The Soummam, Isser and Sebaou river catchments occupied together 16 000 km2; they are regulated by several dams intercepting over one billion m3 of freshwater. The catchments are heavily populated (3 million inhabitants) and mainly submitted to agricultural and household wastes. The objectives of this work were to estimate the loadings in dissolved (TDS) and suspended (TSS) materials into the receiving coasts and to assess the dam effects on their retention, to better understand soil erosion, salinization and shoreline sedimentation. The TDS and TSS were measured two times a month during the period March 2010-February 2011 at the entrances and exits of the dams and at respective river outlets. The TSS was found largely removed in the dams at high rates reaching 60 to 99%. Also, the TDS was highly retained (46 to 81%) depending on the dams. The specific erosion rates reach (28 to 59 t km-2 yr-1 for the TSS and 0.1 to 2.3 t km-2 yr-1 for the TDS according to the river). Even if the TDS were removed in the dams at high rates, their specific loadings were paradoxically very elevated indicating a large soil salinization in lower basins. Despite the great masses introduced into the adjacent coasts, the soil fertility is expected to large alteration.