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The objective of this study is to propose a modelling approach to quantify the contribution of mains coastal catchments of North Africa in sediment and nitrate fluxes to the Mediterranean Sea. We use the Soil and Water Assessment Tool (SWAT) on the biggest coastal rivers, Moulouya (55 860 km2), Tafna (7200 km2), Chelif (44 694 km2) Oued el Kebir (8 824 km2) and Medjerda (23 213 km2). Simulation was performed monthly from 2003 to 2013. The model represents correctly the dynamics of water, sediment and nitrate flux. Rivers carry between 22 .103 to 390 103t yr-1 of sediments and Oued el Kebir contributes with 55% of the total amount, while nitrate fluxes vary from 182 to 1715 t yr-1 and Moulouya contributes with 32% of the total quantity. The simulations show us that the North African dams stocked a large amount of sediment (98%) and nitrates (39%) transported by rivers.

International audience; Abstract Here, we simulate carbon dioxide (CO2) sequestration in 300 major world river basins (about 70% of global surface area) through carbonates dissolution and silicate hydrolysis. For each river basin, the daily timescale impacts under both the RCP 2.6 and RCP 8.5 climate scenarios were assessed relative to a historic baseline (1969-1999) using a cascade of models accounting for the hydrological evolution under climate change scenarios. Here we show that global temporal evolution of the CO2 uptake presents a general increase in the annual amount of CO2 consumed from 0.247 Pg C·y-1 to 0.261 and 0.273 Pg C·y-1, respectively for RCP 2.6 and RCP 8.5. Besides, despite showing a general increase for the global daily carbon sequestration, both climate scenarios present a decrease between June and August. Such projected changes have been mapped and evaluated against changes in hydrology, identifying hot spots and moments for the annual and seasonal periods.