Hydro-ecological relations in the Delta Waters
Hydro-ecological relations in the Delta Waters Hydro-ecological relations in the Delta Waters
In the sedimentation areas, there are clear signs that the ecological commuaities that are directly dependent on the quality of the bed have been disrupted. The long-term pollcy aims of the Wetherlands government are to improve the quality of riper beds and lake beds to such a degree that the aquatic ecosystems can fuaction satisfaccarily, quaranteeing optimum use of the water systems. Short-term policy objectives are to obtain further information about the present quality of the river beds, the causes and effects of pollution and possible means of prevention. Furthermore, uniform standards for the aseessment of all types of soils and clean-up methods for the most polluted locations are being developed. In the last fifteen years almost 80 million m3 of pollnted river sediment have been deposited in the lower reaches of the Rhine, &use and Saheldt. The south-western reglon of the Netherlands can therefore justly he referred to as the sedimentation pit of these rivers. It is essential that clean-up operations in the river basins be iqlemented quickly. However. the eleaning-up af the river beds can on* really be considered when the contamination in the three rivers has been reduced t~ an acceptable level. As a result of consultation at international level, the Rhine riparian states have agreed measures to halve the discharge of a number of major pollutants in the Rhine basin between 1985 and 1495. If necessary, additional measures will be taken after 1995, in the event of failure to achieve the aims lald down in the agreements (such as the elininacion of d~positions of pollutant5 in sediment). The states bordering on the North Sea have arrived at similar agreements with respect to the t-ivers and these will have most effect on the Delta Fn this regard. once the transport of polluted sediment has been halted, a decision may be takw on the cleaning up of the estuary and lake beds. Those areas. where the sediment is of an unacceptable quality in view of the uses te which the wafer is put, are first in line for a clean-up operation. Other important criteria are whether or not: the polluted sediment is gradually heing covered by cleaner sediment as a result of natural processes, the effect which the puSlufed area has upon the surromding environment and the practicability of a clean-up operatioe from the technical and administrative points of view. As such operations are invariably costly, it will be necessary to give
considerable thought to drawing up the list of priorities. Clean-up operatiens are probably uenecessary in areas where a cleaner top layer is being deposited as a result of continuing sedimentation, as is happening in the Hollands Mep and the Land of Saeftinghe. Hwever, in cases where pollutants remain in the top layer and may be released and spread further afield, such measures must be emsidered. The degree of priority to be accorded to cleaning up the area is deteaed by the gravity of the effect of taking no action and by whether the source of palLution has been removed or continues te exist. The polluted harbours in the Eastern Scheldt region are to be cleaned up in the course of 1988. It is certainly worth considering cleasing up the pul$uted sediment in the br, the Nieuwe Menfede and the Biesbosch, as virtually no further deposits of clemer sediment can be expected in these aeeas in future. The need is all the more pressing because it has been prown thAt pollution seriously detracts from the funetion of this azea as a Wure reserve. since simiIar problems with polluted river sed*nts are Ekely to accompany the huildag of dams in other parts of the world with indnstrialixed catchmene areas, the experience gained in the Dutch Delta Project should prove to be generally applicable. Zxtensive hydraulic engineering projects have been csrried out over the last 25 years in the Delta area formed by the rivers Rhine, Meuse and Scheldt. This has resulted in parts of the Delta being divided up (compartmenta15zed) while other parts have been closed off. The time at which many of the opmations involved in dieding up these areas were carried out coincided with a pezioa during which the pollution in the three rivers reached its maximm level (1970-1975).
- Page 1 and 2: Netherlands organkation fw applied
- Page 4 and 5: TNO Commlitee on Hydrological Resea
- Page 6 and 7: 2 RIVER WATER AM) THE QPALITH OF TB
- Page 8: B.J.M. Baptist BIJkswaterstaat. Tid
- Page 11 and 12: This approach will put to use what
- Page 13 and 14: Estuaries that have not been influe
- Page 15 and 16: 2 CHIWGES XN TEE DELTA The Delta ar
- Page 17 and 18: area decltned cnnside~ably, leadins
- Page 19 and 20: Plan, then it is apparent tbt the s
- Page 21 and 22: Tiddl flats df the Eastem Seheldt v
- Page 23 and 24: tracefore possible to convert the a
- Page 25 and 26: Figsrlre 7 Changes in the cadrnrum
- Page 27 and 28: prevention measures are desirable h
- Page 29 and 30: elationships between different spec
- Page 31: Bio-essay Weriments with polluted s
- Page 35 and 36: ShLOUONS, W. and BYSINK, W.D., 1981
- Page 37 and 38: are taken. The first year after the
- Page 39 and 40: The Hollands DiepJnaringpllet is pa
- Page 41 and 42: In 1976 the determination of chlozo
- 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
- Page 49 and 50: 4 WAGBEET MEdSIIRaS TO PEEVBT OR LT
- Page 51 and 52: Table 5 gives estimtes of the phosp
- Page 53 and 54: In principle, two states of equilib
- Page 55 and 56: Zooplankton (Alma affinis) Pike (Es
- Page 58 and 59: EUTROPHICATION OF ESTUAAIES AND BRA
- Page 60 and 61: The average discharge of Xhine and
- Page 62 and 63: and only l-2% cows frm the aive Sch
- Page 64 and 65: highest trophic potential: nutrient
- Page 66 and 67: period 1980-19$3 in an increase of
- Page 68 and 69: model calculations reveal that a ni
- Page 70 and 71: Table 3 PreUmInary carbon budget of
- Page 72 and 73: Water life of Lake Grevelingen
- Page 74 and 75: macrophytes livkg on or rooting in
- Page 76 and 77: less predictable for water managers
- Page 78 and 79: ILWNEWIJK, A.. KEIP, C., 1988. De v
- Page 80 and 81: XBE CHANGING TmAL LAMXiCAPE I N TEE
considerable thought to draw<strong>in</strong>g up <strong>the</strong> list of priorities.<br />
Clean-up operatiens are probably uenecessary <strong>in</strong> areas where a cleaner<br />
top layer is be<strong>in</strong>g deposited as a result of cont<strong>in</strong>u<strong>in</strong>g sedimentation,<br />
as is happen<strong>in</strong>g <strong>in</strong> <strong>the</strong> Hollands Mep and <strong>the</strong> Land of Saeft<strong>in</strong>ghe.<br />
Hwever, <strong>in</strong> cases where pollutants rema<strong>in</strong> <strong>in</strong> <strong>the</strong> top layer and may be<br />
released and spread fur<strong>the</strong>r afield, such measures must be emsidered.<br />
The degree of priority to be accorded to clean<strong>in</strong>g up <strong>the</strong> area is<br />
deteaed by <strong>the</strong> gravity of <strong>the</strong> effect of tak<strong>in</strong>g no action and by<br />
whe<strong>the</strong>r <strong>the</strong> source of palLution has been removed or cont<strong>in</strong>ues te exist.<br />
The polluted harbours <strong>in</strong> <strong>the</strong> Eastern Scheldt region are to be cleaned<br />
up <strong>in</strong> <strong>the</strong> course of 1988. It is certa<strong>in</strong>ly worth consider<strong>in</strong>g cleas<strong>in</strong>g up<br />
<strong>the</strong> pul$uted sediment <strong>in</strong> <strong>the</strong> br, <strong>the</strong> Nieuwe Menfede and <strong>the</strong><br />
Biesbosch, as virtually no fur<strong>the</strong>r deposits of clemer sediment can be<br />
expected <strong>in</strong> <strong>the</strong>se aeeas <strong>in</strong> future. The need is all <strong>the</strong> more press<strong>in</strong>g<br />
because it has been prown thAt pollution seriously detracts from <strong>the</strong><br />
funetion of this azea as a Wure reserve.<br />
s<strong>in</strong>ce simiIar problems with polluted river sed*nts are Ekely to<br />
accompany <strong>the</strong> huildag of dams <strong>in</strong> o<strong>the</strong>r parts of <strong>the</strong> world with<br />
<strong>in</strong>dnstrialixed catchmene areas, <strong>the</strong> experience ga<strong>in</strong>ed <strong>in</strong> <strong>the</strong> Dutch<br />
<strong>Delta</strong> Project should prove to be generally applicable.<br />
Zxtensive hydraulic eng<strong>in</strong>eer<strong>in</strong>g projects have been csrried out over <strong>the</strong><br />
last 25 years <strong>in</strong> <strong>the</strong> <strong>Delta</strong> area formed by <strong>the</strong> rivers Rh<strong>in</strong>e, Meuse and<br />
Scheldt. This has resulted <strong>in</strong> parts of <strong>the</strong> <strong>Delta</strong> be<strong>in</strong>g divided up<br />
(compartmenta15zed) while o<strong>the</strong>r parts have been closed off. The time at<br />
which many of <strong>the</strong> opmations <strong>in</strong>volved <strong>in</strong> died<strong>in</strong>g up <strong>the</strong>se areas were<br />
carried out co<strong>in</strong>cided with a pezioa dur<strong>in</strong>g which <strong>the</strong> pollution <strong>in</strong> <strong>the</strong><br />
three rivers reached its maximm level (1970-1975).
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