Rivers
 The North Sea is fed with water from various rivers.The figure to the left shows the area from where this supply originates. The major rivers which influence the water quality of the North Sea are the Leie/Schelde from Belgium, the Rijn/Maas system from France, Germany, Belgium and the Netherlands, the Themes, the Humber and the Tyne from England and the Ems, the Elbe, the Weser and the the Eider from Germany. |
In Great Britain, the Thames, the Humber and the Great Ouse flow into the southern North Sea. There are no rivers in France that flow directly into the North Sea, but water from the Seine and the Somme enter the North Sea via the English Channel. The Schelde in Belgium and the Maas, Waal, Rijn and IJssel in the Netherlands are the important rivers that flow into the North Sea. In Germany, the important rivers that flow into the German part of the sea are the Ems, Weser and the Elbe. One third of the supply of fresh water to the Northern North Sea comes from melting water out of Norway and Sweden. A few rivers in the north of Great Britain also end in the Northern North Sea, the important ones being the Forth and the Tyne.
Besides water, rivers discharge mud, nutrients and pollutants are discharged by rivers into the North Sea and Wadden Sea. The supply of fresh water via the rivers fluctuates per season and per year. This fluctuation influences the salt level in the North Sea. The supply of mud via the rivers is much less amount-wise than what is transported via the Atlantic Ocean. However, the river mud as well as the water are often very contaminated with all kinds of pollutants, such as heavy metals.
Many contaminants sink at the river mouth because of the slower current and/or the chemical reactions with materials present in the water. Slowly but surely, these contaminants from the river mouths and the coast end up in the North Sea via the ever-present undercurrent. Dredging the waterways, and dumping the material in depots at sea, locally speeds up this process.
| Supply of polluted materials into the North Sea via the Rijn (in ton per year) |
| material | supply 1980 | supply 2000 (% of 1980) | reduction |
| cadmium | 18 | 5.5 (31%) | 69% |
| copper | 500 | 240 (48%) | 52% |
| lead | 320 | 150 (47%) | 53% |
| zinc | 2000 | 810 (41%) | 59% |
| PCBs | 0.22 | 0.08 (36%) | 64% |
| PAHs | 2.1 | 2 (95%) | 5% |
| source: directie Noordzee 2003 |
From the table above, it appears that the greatest success of reduction has been with cadmium and PCB pollution. PAHs remain a difficult material and the discharge of other heavy metals has been more than cut in half.
Weblinks
For more information about the Rijn, see: http://www.iksr.org/.
Source: de Vleet, Ecomare
