Hydro-ecological relations in the Delta Waters
Hydro-ecological relations in the Delta Waters Hydro-ecological relations in the Delta Waters
of the latter is compared with that of Lake Brielle, which is comparable in terms of morphology and residence time. Figure l shows the location of these water systems. Section 4 discusses the possible management measures with which the eutrophicatian problem of the Volkerak-Zoom lake system can be prevented or limited. NOORDZEE Figure 1 Location of Hollands DieplHaringvliet and Volkerak-Zoom lake system
The Hollands DiepJnaringpllet is part of the northern Delta basins, also called the lower area of the peat riiuers. This is the area where two large Western European rivers, the Ehine and the Mewe, discharge into the sea. The river vater enters the area from the east along thtee river channels and can. in principle, reach the sea via two routes. When the Rhine discharge is less than 1700 m3/s tbe Haringvliet sluices ip the west rermtin closed and all the river water enters the sea via the New Waterway. At Rhine discharges abwe 1700 ms/s the Hazingvliet sluices are also used to discharge the riaer water. These sluices are, haqeaer, ~nly opened at low tide. This management of the hringvliet sluices obviously has repercussions on the water movement in the Hollands DieplHaringvliet and henee also on the eutrgphicatios sitnatLon. The eutrophlCation situation of the basins ~im he characterized as falLows. Large amounts df nitrogen and phosphate are brought in by the rivers, thns the concentrations of nutrienks are high. Howevet, it is striking that in these waters a low biamass of algae U usually formd. Rlsa. tlie bbmass of algae usually decreases fxom east torest; as a ~le, the £eves* algae are found near the Wingvliet ailuices. Generally. fev blue-green algae oceur in these waters and the trausparency is reasonable on the whole; near the Karisgpliet sluices a twsperencg of 1 to 1.5 m is regularly found. The relatively low biarsasses of algae are often attributed to the influence of toxic substances. It will be shown below that the watez movemat provides a plausible exalanation. Figure 2 shows the chasges in mean snmaer Level of chlorophyl along che traject from Lohith to the Earingttliet aluices for the pear 1982. Chloropbyl is an indicator of the amaunt of algae in the water. From Figure 2 it can be seen that there is a clear decrease in the biomfass of algae along the traJect. However, the picture changes if we look at figures from other years. Figure 3 shows the mean smmer levels of chfwrdphyl between Lohith and ehe Earinpliet slaices in 1976, L982 and 1987.
- Page 1 and 2: Netherlands organkation fw applied
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- Page 25 and 26: Figsrlre 7 Changes in the cadrnrum
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- Page 33 and 34: considerable thought to drawing up
- Page 35 and 36: ShLOUONS, W. and BYSINK, W.D., 1981
- Page 37: 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
- Page 47 and 48: Laks Volkarek ---- Lake Zoom 0.40 0
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of <strong>the</strong> latter is compared with that of Lake Brielle, which is<br />
comparable <strong>in</strong> terms of morphology and residence time. Figure l shows<br />
<strong>the</strong> location of <strong>the</strong>se water systems.<br />
Section 4 discusses <strong>the</strong> possible management measures with which <strong>the</strong><br />
eutrophicatian problem of <strong>the</strong> Volkerak-Zoom lake system can be<br />
prevented or limited.<br />
NOORDZEE<br />
Figure 1 Location of Hollands DieplHar<strong>in</strong>gvliet and Volkerak-Zoom lake<br />
system
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