The Scheldt estuary from past to future: setting the scene

The Scheldt estuary, the tidal part of the river Scheldt, is 160 km long, which is little less than half the total length of the river! This situation came about since the Middle Ages due to a complex interaction between sea level rise and large scale embankments resulting in a gradual upstream movement of the tidal limit. The presence of tidal marshes and flats along the whole salinity gradient is a rather unique feature and their inherent biological value resulted in many conservation measures. However, the estuary is nowadays subjected to many anthropogenic pressures resulting in habitat loss and degradation, bad water quality and increased risks of inundation. Some major trends will be presented. Water quality is improving, oxygen levels increased, heavy metal concentrations decreased but nutrient loads still increase and signs of eutrophication can be seen. Major morphological changes occurred and very high sedimentation rates on both tidal marshes and flats result in a change of inundation period, on marshes leading to major changes in vegetation. Towards the future we will have to deal with major new challenges: what will be the impact of global change (sea level rise, changes in discharges), the impact of changes in land use and management in the Scheldt basin, morphological changes in the estuary due to further dredging etc. The possible consequences of some of these expected changes will be explored