Hydro-ecological relations in the Delta Waters

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wind erasson, desaliuation, aeration, physical and chemical ripening and decalcification). The time scale of these processed differs from some manths or years lwind erosion) to tens or hundreds of years (decalcificetion). In the beg-ing t?e effects of theae individual processes are quite clear. Wen the new ecosystems grow older it is getting more and mors difficult to separate them from each other and from the internal aynamics of the developin& ecosystems theirselves. Figure 7 (acbording to Drost and Visser. 19111) gives a pod fdea how the abiotic envixo~meut of different soil types behaves in relation €0 desaUnation. On well percolating soils desalination goes vezy fa&. Mter some years there is already a rathez large freshwater body in the soil. Glycophyloue hmbs and grasses can soon caloniee the bare sou and mrwal shrub and then woodlmd deve,loplaent follows. CLay Layers in the wail profile stagnate desalination and then this process can take tens of years. In autumn and Winter the sail is satiuaced fast and most of ttle rain water will stagmac@ and ran off supetficially. Aere only the upper soil layers will have E freshwater body and this will evaporate cempletely in stmmer. In tthis type of habitat halophylous plant species dominate in the primary vegetation development. !Frees and shrubs can hardly colonize the vegetation giving it tbe character of open grassland for a long time. 3.3 Management of water and land Uatex manasement is especially important on flat shores, where emaller or larger areas can be inmdated during some time. This is of great importance for €he suraival and germination oppnrtunitiea 4f certain plant species. A good exanple how this can influence the fauna is fouad n Lake Creuelmen. Aere the bird species of scarcely vegetated shell shores and beaches axe declining (e.g. Kentish Plover, see Fig. 5). bcaose ef continuing vegetation development. Ffaybe there is a possi- bility to maintain a larger area of this type of breeding habit& by raising the waterlevel OS the lake in autumn or winter time during several weeks. Then a lareer part of the shore is inundated by saline water, slowing down further vegetation development.
In the terrestrial habitats it is of weat impartance how the nutrient cycles of the ecosystem and the structure of the vegetativn are influawed. The nutrient cycles detenatee growing and feeding conditions for plant and animal species, whLle vegetation structure is of great iaqrortance for their survival. Rmtghly speaking we can distinguish three ways af nature managemeqt: spontaneous developdent. rcewing and grazing. Each of these managerneat types has its om results and (financial) costs. Sponfaneous development will lead to woodland ultinatelp, a l e mowing keeps areas open and rich in herbs. Orazing is in between these two types and the rcanlt depends on gra~ing intensity. It is an attractive type of management to create a habitat with a ~aried structure of grassland and shrubs in a semi-natural way. Grazing anlmaLs l~ndigenrms herbivorous herds as well as domestic cattle) we large areas in traditihsl patterus. Some parts of the area are (year after year) more intensively grazed than others. In this way Fazing can enlarge the differentiaties of the abiotic envirpmenc creating additional stimuli for mre diversity in developing ecosystems. In the lens run it will not only result in grassland. Even for natural woodkd development grsing (of course in very low densities) can be a good cyse of management. 4 BALBNCE OF ECOSYSTEM DETFELBFXE4T UP TO BOW The fitst embankment of a large estuary in the South-West Netherlands tbok place some 30 years ago (Lake Veere, 1961). Since that time several othsr areas folloved. with difTerent abiotic enviroweuts and different types of water systeqts. As indicated above ecosyste& i3evrlop- ment is still going on and eves in the oldeat aress it will take tens or even hunrtreda of years before the new t~rresrriai habitats will be stabilized. Notwithstanding these facts we ri1.l try to make up some balance fxom a pine of view of nature conservativn and manaseoee. Firstly we wst natice that chere is a great loss of valuable (semi-) terresrrial habitats in the esttmfes of the South-West Wetherlands as a consequaRce of the Delta Work$. (The lv,ags of aquatic ecosystems and tidsl flat6 is leet out of oonsideration.) After the enclosniuze of the
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Netherlands organkation fw applied
Page 4 and 5:
TNO Commlitee on Hydrological Resea
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2 RIVER WATER AM) THE QPALITH OF TB
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B.J.M. Baptist BIJkswaterstaat. Tid
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This approach will put to use what
Page 13 and 14:
Estuaries that have not been influe
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2 CHIWGES XN TEE DELTA The Delta ar
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area decltned cnnside~ably, leadins
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Plan, then it is apparent tbt the s
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Tiddl flats df the Eastem Seheldt v
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tracefore possible to convert the a
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Figsrlre 7 Changes in the cadrnrum
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prevention measures are desirable h
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elationships between different spec
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Bio-essay Weriments with polluted s
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considerable thought to drawing up
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ShLOUONS, W. and BYSINK, W.D., 1981
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are taken. The first year after the
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The Hollands DiepJnaringpllet is pa
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In 1976 the determination of chlozo
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, 0.66 m 0,s - 0.02 1989 I 0.86 - 0
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Table 3 Eutrophication of the Volke
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Laks Volkarek ---- Lake Zoom 0.40 0
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4 WAGBEET MEdSIIRaS TO PEEVBT OR LT
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Table 5 gives estimtes of the phosp
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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$3 in an increase of
Page 68 and 69: model calculations reveal that a ni
Page 70 and 71: Table 3 PreUmInary carbon budget of
Page 72 and 73: Water life of Lake Grevelingen
Page 74 and 75: macrophytes livkg on or rooting in
Page 76 and 77: less predictable for water managers
Page 78 and 79: ILWNEWIJK, A.. KEIP, C., 1988. De v
Page 80 and 81: XBE CHANGING TmAL LAMXiCAPE I N TEE
Page 82 and 83: The storm surke of L&Z1 A.D., knorm
Page 84 and 85: osi* rn@8IOIP m .SL 4 Has F~~ULB 3
Page 86 and 87: During the 19th century man starts
Page 88 and 89: mudflats have retreated some 100-20
Page 90 and 91: aq811~33a.e~ pue 3pTatlJS uxaJsafi
Page 92 and 93: Erosion by waves of sandy shoals (c
Page 94 and 95: Lt has been estimated that the sedi
Page 96 and 97: Implementafion of the Delta Project
Page 98 and 99: ECOLOGICAL DEVELOWdENT OF SALT MAKS
Page 100 and 101: fn tidal water systems sedimentatio
Page 102 and 103: hierarchical position. Tn the egtua
Page 104 and 105: Of course. tke environmental change
Page 108 and 109: Fonner tirtal flats with saltmarsh
Page 110 and 111: Grevelingen. Lake Veere and Krammer
Page 112 and 113: As mentioned above aa important que
Page 114 and 115: A seaond important perspective for
Page 116: BEEEXNX, W.D. and 80ZBf&. J. L9M. T
Page 119 and 120: are determining the dfstrlbution af
Page 121 and 122: this volume or in Duutsaa, et aL, 1
Page 123 and 124: artificial waterflow was created af
Page 125 and 126: of waterbirds occur regulsrly. The
Page 127 and 128: . DISTRIBUXIOBI OF WATEJBIRoS OVER
Page 129 and 130: small bird$ extludiag them vill net
Page 131 and 132: In order to lsok for relatiouehips
Page 133 and 134: Table 3 Biomass of macroroobenthos
Page 135 and 136: freshwater basins. Clearly the pres
Page 137 and 138: scmthem bottueary o-f the winter di
Page 139 and 140: OCLURRENCE AND DIET QF B ~T .tUQ 80
Page 141 and 142: 5.2 H- factors Next to all fartors
Page 143 and 144: Bewick's Swans (Cygnus columbariusl
Page 145 and 146: m's activiries do not always have t
Page 147 and 148: measure affecting food supply or av
Page 149 and 150: DOQiWT$QS, G. 4 TWISK, F., 1987. De
Page 151 and 152: MEININGEB, P.L. and HAPEREX, A.M.M.
Page 153 and 154: PISCIVORES Litfle Grebe Great Crest
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IPYBRO-EGOLOOIOAL BELATIONB ZN THE
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apart from upstream purification; -
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Storm surge barrier Eastern Scheldt
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- In addition to existing managemen
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Nature is pliable. Belattvely young
Page 166 and 167:
Ro. 1. No. 2. SQ. 3. Investigations
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25. The relation between water quan
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Hydro-ecological relations in the Delta Waters

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