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2. 1. Introduction

This report synthesizes the proposed zonation of the 4 TIDE estuaries: Schelde, Elbe, Weser and Humber. The zonation can be necessary for the spatial distribution resolution and to be able to compare the estuaries. For a common basis, zones of equal properties have to be chosen. This zonation approach will be used in cases when it is more sensible to compare only certain areas of the estuaries instead of considering the whole estuary, e.g. for the different issues of ecological functioning, research questions, monitoring schemes, measures and management issues, etc. This is required in TIDE, more specifically in the work packages 3 and 4 considering the ecosystem services survey, the conflict matrix and certain aspects of the interestuarine comparison for ecology, hydro- and geomorphology.

The zonation approach takes the following conditions into account:

1. The zonation system should be flexible enough to cover different issues.
2. It should allow the direct comparison of certain areas of each estuary.

The first condition is met by having a nested zonation, consisting of 3 or 4 scale levels: the whole estuarine system (the estuary corresponds to one compartment or zone) on the first level and more compartment numbers on every scale below. It is important to have a good representation of zones on every scale. The second condition is met by the agreement to present the estuarine results according the standards that were set at the Bremen meeting (September 2010) and the Rouen meeting (June 2011): setting km “0” of all estuaries at the inland tidal boundary on the longitudinal axis and using the Venice system for a comparable zonation between the estuaries. Considering only the Venice system, the freshwater zone is too long to compare as a whole between estuaries. Therefore, it was decided to split the freshwater zone according to morphology, residence time and/or usage, based on expert judgment by each TIDE-partner.

In this report, first the levels of the zonation are described, maps indicating the single zones are presented, and the basic characteristics of these zones (length, volume, surface, average depth, salinity, residence time, anabranches and tributaries) are listed. Residence times listed herein give a good first indication, but will be uniformly recalculated by the hydrogeomorphological workgroup for all estuaries within TIDE, taking into account the tide.

Secondly, the zonation based on the Venice system is given for all estuaries. Therefore, salinity calculations are carried out, based on the median values of chlorinity for the 6 year period (2004-2006), wherefore the interestuarine comparison will be performed.

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