Hydro-ecological relations in the Delta Waters

Bicropollutants (heavy metals and mganic compounds) became attaohed to
the fines in the sediment carried by the rivers, and this lea to the
Delta region also being affected by these contaminants. Ifowever,
because of compartmsntalization. eertain areas, namely Lake Grevelingen
and the tidal basin of the Eastern Scheldt, escaped the wave of
pollution. The qnautities of micropallutants in these areas are very
€lose to natural backgmund levels. The explanatian for this is that
the compartmentalization of these areas waa cmpleted before the
pollucibn in the Rhine and Meuse reached such high levels.
m contrast, the closure of the Itaringvliet esfuary led to the
formation of new sedimentation areas just prior to the time at which
ehe pollution in the mine and Wuee reached a peak. Thus layers of
contaminated material have settled in these sedimentation ar-S.
30% of the tutal am~unt of silt transported by the rivers Bhine and
Meuse is depasited in these areas.
Almost
Estuaries that hare mt been influenced by closure operations can also
undergo significant tempmrary sedimentation effeots. An uample of this
is the Land of Saeftinghe in the Western Scheldt estuary. h a result
of a rise in the sea level and a deepehg of the shipping channel, the
difference between low and higher water hqs increased which. in turn,
had resulted in a sigaiftcz~tLy greater deposition of silt on the
mudflats and salt marches. Blmosr 254: of the silt crsnspdrted by the
river Sehaldt settles in these areas. Although relatively little is
born about the effects that conraminated beds haae on the aquatic
ecosystem, there are clear signs that eecelogical contmu~iities whPch &re
directly dependent on the river bed environment can be disrupted. In
addition, the aouots of pollutants found in Certain organisms and
plants now exceed the maximum acoeptable levels for human cm%umption.
Future clean-up operations could be considered £m tbe conraminated
sedimentation areas when the level of pollutian from discharges into
the river baeiw has been sufficiently reduced. In view of th8 scale
and eeent of the sedimentatim layer concsrned, no solutions have yet
been fuund to this pmhlm.