Hydro-ecological relations in the Delta Waters
Hydro-ecological relations in the Delta Waters Hydro-ecological relations in the Delta Waters
Table 1 PCB levels in ees of grebes from the Haringvliet basin and sore clean reference amas (values in ~g/kg) basin areas PCB 138 4 900 - 18 500 120 - 1 450 PCB 153 9 MO - 16 500 205 - 2 $50 PCB 186 1 850 - 3 450 10 - 195 Recent research also show8 that cormrants, a fish-eat*g spaeies at the end of the fopd chain, are reproducing far leas snecessfully iU the northern part of the Delta region (Biesbasch) than in other areas (Boudewijn, et al. 1989). In a number of colonies along the major rivers (IJssel. Rhine and Waal) the reproduction rate is two to three rirpes higher than in the Biesbaach, and it is four tines highex in areas witb a relatively low level nf palltLTian. (See Table 2). Table 2 Number of puns leaving the nes per clutch, in a d e r connorant colonties in 1988. of &ss with a MBj or river areas Biesbosch reiatfrely low level of gollrttion OV Oude Venen (Friesland) BW B~ede Water CVoorne) W Wijhe (Gelderse IJseel3 0 OZst (Gelderso TJssel) P Pannerden (Upper Rhine) W Baaften (Waal) bB Dordrse BSeabosch
Bio-essay Weriments with polluted sediment from Due of the smaller harbours in the Delta region (&resicens) revealed effects on oyster larvae (Crassostrea Awulatal and a ernstacean Lhthypreia). Even when B large proportion of Clew sediment was added to the polluted harbour sludge, mortality rates were demonstrably affected by pollution (Hnrk, 19883. The effects of increasing pollution in water md riverbeds are al-so noticeable in the Western Srheldt estuary. The popuLation of hatbaur seals (Phoca vitulina) has now disappeared. Food chains in rhe eastern part of the estuary have been dfsthed and the number of benthic organisms significaatly raduced. It is acknowledged that the amounts of cabmiwu now exceed acceptable leveLs for hum consumption. particularly in flounder (Platickthys flesus), in shellfish such as mussels (Mytilus edule) aad in sea plants such as Aster tripolium and Salicornfa spec., foutld in the Lad of Saeftinghe area. 6 CONCLXISIONS AI43 FINAL ReMaaKS Although water quality and the condition of the beds we*e not taken intn consideration at the time of the origtnal decisions concerning the phasing and implementation 05 the Delta Plan, it is now recognized that the separation of parts of the Delta from the waters of the Rhine and Eeuse, as part of the compartmentalization programme for the regiwn, has played a significant role in wtntainSs& a satisfactory level of quality in the majority of the beds in the Delta. As a result, the quality of the sediment in tlle central secrion of the estuary is clese to natural backgrrrwd levelS. However, the closure of an estuary such as the Rarin8vliet ean lead to large amounts of polluted river ~ilt settling in new sedimentation areas. An other ntethod af controlling the distribution of contaminated rmaterial is to limit the tkrou~hpm of water if sluices for water management are available in the colnpartment~llzation-dams. This idea has, for instance, been incorporated into the plan for managing the quanrity of water of Lake Zaoin.
- Page 1 and 2: Netherlands organkation fw applied
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- Page 35 and 36: ShLOUONS, W. and BYSINK, W.D., 1981
- Page 37 and 38: are taken. The first year after the
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- Page 43 and 44: , 0.66 m 0,s - 0.02 1989 I 0.86 - 0
- Page 45 and 46: Table 3 Eutrophication of the Volke
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- Page 58 and 59: EUTROPHICATION OF ESTUAAIES AND BRA
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- Page 70 and 71: Table 3 PreUmInary carbon budget of
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Table 1 PCB levels <strong>in</strong> ees of grebes from <strong>the</strong> Har<strong>in</strong>gvliet bas<strong>in</strong> and<br />
sore clean reference amas (values <strong>in</strong> ~g/kg)<br />
bas<strong>in</strong><br />
areas<br />
PCB 138 4 900 - 18 500 120 - 1 450<br />
PCB 153 9 MO - 16 500 205 - 2 $50<br />
PCB 186 1 850 - 3 450 10 - 195<br />
Recent research also show8 that cormrants, a fish-eat*g<br />
spaeies at<br />
<strong>the</strong> end of <strong>the</strong> fopd cha<strong>in</strong>, are reproduc<strong>in</strong>g far leas snecessfully iU <strong>the</strong><br />
nor<strong>the</strong>rn part of <strong>the</strong> <strong>Delta</strong> region (Biesbasch) than <strong>in</strong> o<strong>the</strong>r areas<br />
(Boudewijn, et al. 1989). In a number of colonies along <strong>the</strong> major<br />
rivers (IJssel. Rh<strong>in</strong>e and Waal) <strong>the</strong> reproduction rate is two to three<br />
rirpes higher than <strong>in</strong> <strong>the</strong> Biesbaach, and it is four t<strong>in</strong>es highex <strong>in</strong><br />
areas witb a relatively low level nf palltLTian. (See Table 2).<br />
Table 2 Number of puns leav<strong>in</strong>g <strong>the</strong> nes per clutch, <strong>in</strong> a d e r<br />
connorant colonties <strong>in</strong> 1988.<br />
of<br />
&ss with a MBj or river areas Biesbosch<br />
reiatfrely low<br />
level of gollrttion<br />
OV Oude Venen (Friesland)<br />
BW B~ede Water CVoorne)<br />
W Wijhe (Gelderse IJseel3<br />
0 OZst (Gelderso TJssel)<br />
P Pannerden (Upper Rh<strong>in</strong>e)<br />
W Baaften (Waal)<br />
bB Dordrse BSeabosch
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