| The objective of this project is to develop knowledge and methods for the implementation of the Water Framework Directive and other EU directives such as the Bird Directive and the Habitat Directive. In cooperation with the Directorate-General for Public Works and Water Management, WL / Delft Hydraulics worked on the development of a spatial analysis tool for ecological assessment: HABITAT. In this project, the applicability of Habitat for the implementation of the WFD and Bird and Habitat Directive was explored further. One of the possible applications which were examined is the use of Habitat to assess possible and feasible measures to achieve the environmental objectives. In order to search for possible applications of HABITAT and demonstrate how it may be used, a case study was conducted in cooperation with the national Institute for Inland Water Management and Waste Water Treatment (RIZA). For IJssel Lake, the potential occurrence of the Zebra mussel (Dreissena polymorpha) was modelled based on maps of environmental conditions. The results correspond reasonably well to the actual occurrence. The abundance of the Zebra mussel is one of the objectives of the WFD. An imaginary objective to be set as the exact objective for heavily modified waters has not yet been established. Using HABITAT, a spatial image was created of the limiting environmental conditions such as water level, soil type, and orthophosphate concentrations. Measurements should focus on improving conditions resulting in the largest suitable area. However, this example also demonstrated that some conditions cannot be changed as a result of unrealistic measures and consequent failure to achieve the objectives. This information can help policymakers with the formulation of environmental objectives. Based on this example, a document was written and other EU Directives studying the possible applications of Habitat for the WFD. This document has been sent to several water managers. A second case study focused on the river IJssel. In a discussion with RIZA, several steps which must be followed to meet the environmental objectives have been formulated and assessed for the possible application of HABITAT. In this case we studied whether a set of measures resulting from the project ' Room for the River ' would bring us closer to achieving the ecological objectives in and along the river IJssel. To perform this case study, the HABITAT tool has been filled with habitat-models for macrophytes and fishes. A description of the hydro-morphological conditions was derived from simulations with the WAQUA model for the IJssel. However, this model was calibrated for extreme hydrological situations through which the final results deviate from the actual situation. We propose to make these types of models suitable for the simulation of average hydrological conditions as this mainly determines the ecological conditions which make these models useful in the process of selecting effectiveness measures. Finally, another conclusion from the case studies is that more knowledge rules are needed with regard to impact-effect relationships. The current assessment method for Dutch water bodies presently exists of a large number of species. It is probably not feasible to create knowledge rules for all these species. Therefore, we propose to select indicator species or group species and set knowledge rules for these groups. |
