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Trilateral Wadden Sea Plan Eighth Trilateral
Governmental Conference
on the Protection of the
Wadden SeaStade, Germany,
October 22, 1997
6 Estuaries The estuaries in the trilateral cooperation are delimited on the landward side by the mean brackish water limit, and on the seaward side by the average 10‰ isohaline at high water in the winter situation. In terms of the Wadden Sea Area, the estuarine areas are thus the areas between the 10‰, isohaline as defined at the sea side up to the mean brackish water limit of the rivers, and at the landward side of the rivers, the areas outside of the main dikes or, where the main dike is absent, the spring-high-tide-water line including the corresponding inland areas to the designated Ramsar and/or EC-Bird Directive areas.
Estuaries include the river mouths with a natural water exchange with the Wadden Sea. Such brackish areas belong to the transition zone between rivers and tidal waters. There are four such estuaries in the Wadden Sea Area with 'open access' to the Wadden Sea, namely the Varde Å in the Danish Wadden Sea Area and the Elbe, the Weser and the Ems in the German Wadden Sea Area, whereas no estuaries have been preserved in the Dutch part.
Status The estuaries serve as a migration route for migrating fish like Houting, Salmon, Trout and Sturgeon. They are bordered by salt marshes in which Reed and Sea Club-rush can dominate large areas, instead of Sea-purslane and other salt marsh species. The flocculation of clay minerals stands for a muddy soil, with a benthic fauna that suits the needs of birds like Avocet, Redshank and Spotted Redshank. The brackish salt marsh vegetation produces more biomass than any other salt marsh, attracting large numbers of ducks and geese that feed on the vegetation and the seeds that are released during the autumn.
Brackish areas are also important inundation areas. Many of these brackish salt marshes have been reclaimed and several river outflows (especially the smaller ones) have sluices that prevent natural mixing of fresh and salt water and the establishment of transition zones. In The Netherlands, initiatives have been taken to modify sluicing regimes aiming at achieving more natural transitions between fresh and salt water.
The estuaries of the rivers Elbe, Weser and Ems constitute the seaward access routes to the major German sea ports. Management of these marine navigation routes is a matter of public interest and regulated by law. The Elbe and the Weser estuaries are among the most industrialized regions of the Wadden Sea Area.
The Varde Å estuary has morphologically remained in its natural state, but is subject to a very intensive agricultural exploitation.
Targets Protection of valuable parts of the estuaries.
Maintaining and, as far as possible, restoring the river banks in their natural state.
Assessment The ecological importance of the river Ems is, in comparison with the other estuaries, to be valued as high, with a good water and sediment quality. The situation has been aggravated over the last ten years i. a. with the deepening of the river and the associated ecological impacts. In spite of increasing shore protection with artificial constructions, the river foreshore is in a semi-natural state with a relatively extensive agricultural use.
The development of the Weser estuary for shipping, the embankment of river banks and harbor and industrial developments have resulted in significant alterations in morphology, hydrography, flora and fauna. One of the consequences is that the deposit of mud in the outer part of the estuary is larger than in the natural situation and also, that a cloud of dispersed material has emerged.
Dredging and embankment of the river Elbe, and the concomitant developing of industries and harbors in the area, have significantly changed the ecological system. There are only very few sites in the estuary which can be regarded as natural or undisturbed. The remaining foreshore areas are protected by artificial groins and may be defined as semi-natural foreshore areas.
The Varde Å estuary has been maintained unregulated, whereas the agricultural use of the marshes and meadows has been intensified.
How to proceed The relevant policies for water and sediment and brackish marshes also apply to the relevant elements of the estuaries.
In considerable parts of the German estuaries, human use has the priority. Shipping routes and harbors are to be managed for their intended purposes. It is, nevertheless, necessary to maintain and restore ecological functions of the estuaries. To this end, a concept is currently being worked out for the German estuaries with the aim to examine possibilities for protection of valuable parts and maintain and, as far as possible, restore the river banks to their natural state.
In the Varde Å estuary, an extensification of the current agricultural use is the aim and a restoration project has been initiated.Assessments of the environmental impacts of new activities, compensation and mitigation, and restoration projects are central elements in policy and management. Where necessary, the protection of valuable parts of the estuaries not yet protected must be undertaken.
The sluicing regime must be modified in some areas to obtain a more regular volume of fresh water drained off from the mainland and to ensure better opportunities for migrating fish.
6.1 Trilateral policy and management The policies for important elements of the estuaries, i.e. the water, the salt and brackish marshes, and the rural area, have been formulated in Chapter 2, 3, 8 and 9 respectively. The relevant parts of these policies also apply to valuable parts of estuaries. It concerns here, in particular, dumping of dredged material, agriculture, hunting, fisheries, recreation and energy.
6.1.1 The extension, or major modification, of existing harbor and industrial facilities and new construction shall be carried out in such a way that the environmental impact is kept to a minimum and permanent, or long lasting, effects are avoided and, if this is not possible, compensated. In the Conservation Area, new, not yet approved plans for new construction, as well as for the extension or major modification of existing harbor and industrial facilities, are not allowed unless such is necessary for imperative reasons of overriding public interest and if no alternative can be found. (Identical with 4.1.5).
6.1.2 The deepening of shipping lanes in the estuaries will be carried out in conjunction with an overall assessment of how to compensate and mitigate the measures.
6.1.3 The impact of dumping dredged materials will be minimized. Criteria are, amongst others, appropriate dumping sites and/or dumping periods. (Identical with 4.1.15).
6.1.4 Valuable parts of the estuaries will be protected and river banks will remain and be restored in their natural state, as far as possible.
6.1.5 The transition zone between fresh and salt water should be as natural as possible.
6.2 Trilateral projects and actions 6.2.1 A joint report of existing inventories and their results to determine the valuable parts including river banks and the legal and/or administrative protection of valuable areas in the estuaries. The results will be discussed on a trilateral level, for example, to determine possibilities for restoration projects including the restoration of transition zones.
6.2.2 The results of a Dutch study into the best locations for the restoration of estuarine transition zones (potential areas: Westerwoldsche Aa, IJsselmeer, Amstelmeer, Lauwersmeer and polders) where fresh/salt water exchange takes place (pumping stations) will be evaluated, after which additional measures might be taken.
6.2.3 In Lower Saxony, a concept is currently being worked out for the German estuaries with the aim to examine possibilities for the protection of valuable parts and maintain and, as far as possible, restore the river banks to their natural state.
6.2.4 A trilateral evaluation of the results of the above mentioned studies which will be taken into consideration in the further elaboration of the Plan.
6.2.5 The initiation of a project, in close cooperation with responsible port authorities, with the aim of investigating how harbor developments and environmental protection can be reconciled.
6.2.6 The evaluation of the running reintroduction project of the Houting in Denmark and Schleswig-Holstein and the consideration of further actions in other rivers of the Wadden Sea.
6.2.7 The restoration of the Varde Å estuary through extensifying agricultural use and restoring natural hydrological conditions.
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