In the TIDE project a zonation approach was set up for cases when it was more sensible to compare only certain areas of the 4 estuaries Scheldt, Elbe, Weser and Humber instead of considering the whole estuary. In order to be able to directly compare certain characteristics e.g. ecological functioning, research questions, measures and management issues, basis zones of equal properties were chosen.
The zonation approach consists of a nested zonation 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. The project partners agreed on setting km “0” of all estuaries at the inland tidal boundary on the longitudinal axis and using the Venice system for a comparable zonation, even when this approach differed from those used by the different partners in the past. The freshwater zones were divided according to their morphology, residence time and/or usage, based on expert judgment by each TIDE-partner because they were too long for the intercomparison exercise.
This report describes the levels of the zonation and provides maps indicating the single zones as well as the basic characteristics of these zones (length, volume, surface, average depth, salinity, residence time, anabranches and tributaries). Residence times listed herein gave a good first indication, but they will be uniformly recalculated for all TIDE estuaries taking into account the tide.
For the zonation based on the Venice system salinity calculations were carried out, based on the median values of chlorinity for the 6 year period (2004-2006).
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