The Rhine/Meuse Estuary

Abstract

The Rhine is a major river (length 1328 km, catchment area 224,000 km2) flowing through several densely populated and industrialized areas in Switzerland, the Federal Republic of Germany, and the Netherlands, draining parts of France and Luxembourg as well. Important contributions of contaminants originate from the rivers Aare, Neckar, Main, Lahn, Wupper and Ruhr. The connections of the Rhine with the North Sea are the (open) Nieuwe Waterweg and the sluices in the enclosure dams of Ysselmeer and Haringvliet (Fig. 1). The long-term annual mean discharge (1901–1975) is 2200 m3S−1 at Lobith (Fig. 2) (RIZA 1982; RIWA 1984). Seasonal variations are between 980 and 9400 m3S−1, mainly due to irregular precipitation (Fig. 3a represents monthly averages for 1982 and 1983). About 10% of the Rhine discharge is directed through the river Yssel that discharges into the Ysselmeer (with a surface area of 1230 km2 and a mean depth of 4.5 m). The discharge through the Yssel is kept above 285 m3S−1 for shipping purposes. The residence time of water in Ysselmeer is about 6 months before it is sluiced into the Waddensea. Because of the strong decrease in water velocity at the entrance of the lake, the bulk of suspended matter is deposited in the Ketelmeer area. Turbidity in the Ysselmeer is lower, and biological activity, pH, and dissolved oxygen concentrations are higher than in the Rhine and Yssel rivers. This affects the behaviour of several contaminants.