Hydrological characteristics of the Oualidia and Sidi Moussa lagoon complex (Morocco)

Abstract. As part of the hydrological monitoring of the Oualidia-Sidi Moussa lagoon complex during 2014-2015 period, a network of hydrological stations was set up in both lagoons. These stations were selected based on the needs of algaculture and shellfish farming trial facilities established within the lagoons. Monthly hydrological monitoring allowed for the characterization of their ecosystem through the seasonal variability of physicochemical parameters during low and high tide cycles. At low tide, the waters are cold, nitrate-enriched throughout the year, and experience significant warming in summer and autumn. At high tide, the waters are generally saltier from upstream to downstream, as the less dense freshwater masses remain localized in the upstream areas of the lagoons. The shallow upstream parts of both lagoons are characterized by a high percentage of organic matter due to the dominance of fine sediment, a result of weak hydrodynamics. In contrast, downstream areas are dominated by coarser sediment and have a very low organic matter content, facilitated by the presence of stronger currents, especially during spring tides.