In the rural and semi-rural environment many sources of contamination may impact surface water quality. In addition to nutrients from agricultural activities, contaminants occurring at low concentration so-called trace contaminants are a growing issue for water quality. To address this issue and investigate mitigation measures, the Berlin Centre of Competence for Water (KompetenzZentrum Wasser Berlin) developed a collaborative research project called Aquisafe, in association with the Indiana University – Perdue University Indianapolis (IUPUI), the German Federal Agency for the Environment “Umweltbundesamt” (UBA) and Veolia Water. The project aims at investigating mitigation zones such as constructed wetlands or riparian zones to improve the quality of surface water with respect to diffuse pollution. Before using models and conducting field experiments, the first part of the project is an extensive analysis of the nature, occurrence, and risks of source water contamination in rural and semi-rural areas. This is the subject of the poster. The objectives of this first part of the project are (i) to provide background information on surface water and its use in Europe, particularly regarding drinking water supply, (ii) to investigate the characteristics of the families of pollutants that are potentially of interest, and finally (iii) to select the most relevant trace contaminants to be investigated in future field experiments. To reach these objectives, an extensive literature review was carried out, using different criteria to select the relevant families of pollutants and then the individual substances. The screening process is currently in progress and includes a collection of substance characteristics that will be used for subsequent selection, such as toxicity or persistence in the environment. Key figures and information were collected concerning the nature, use and vulnerability of surface water in Europe that provides 70% of total water abstraction (drinking water, industry and agriculture) in Europe. The main pollutant families of interest for the screening process were the following: pesticides used in agriculture (e.g. glyphosate or isoproturon), pollutants coming from the spreading of animal waste on land (e.g. veterinary pharmaceuticals or hormones), pollutants coming from the spreading of sludge from wastewater treatment plants (e.g. heavy metals or hormones), pollutants from natural areas (e.g. flame retardants in forests), and pollutants from transportation networks (e.g. heavy metals from vehicles). Consequently in a rural or semi-rural area, the land use in the watershed plays a key role in the selection and assessment of priority pollutants coming from diffuse sources and entering surface waters. The work is still in progress concerning the review of pollutant families, and will lead to the final screening at substance level, providing a list of key contaminants for the other work packages within the Aquisafe project. Eventually, corresponding data for the same issues in the United States will be added and provide a comparison between the two continents.

The application of hydrodynamic sewer modelling allows for detailed description of complex hydraulic situations. However, for large systems long-term calculations with hydrodynamic models still require high computation times. This paper shows a possibility to overcome this problem by using a hybrid sewer model, which is a conjunction of conceptual and mechanistic modelling approaches to combine the calculating speed of conceptual models and the accuracy of mechanistic models in one model. The implementation of a hybrid sewer model was performed and tested in two case studies, in Berlin (Germany) for 6 representative catchments and in Herent (Flanders, Belgium) for one sewer system, using the hydrodynamic modelling software InfoWorks CS. Besides the motivation of the case studies on the sewer systems in Berlin and Herent this paper presents the methodologies developed for a hybrid simplification of the sewer network model, considering the calibration of the simplified network as well as the evaluation of the simplification performance. The use of a hybrid model for both case studies is then evaluated and the transferability of the methodologies is discussed.

Within the project SAM-CSO it shall be tested if the Open Modelling Interface and Environment (OpenMI) can be applied to link models of the Berlin sewerage (modelled in the urban drainage software InfoWorks CS,Wallingford Software) to a river water quality model. This report gives an overview on the OpenMI and its application. Chapter 1 outlines the general background of integrated water management and integrated modelling as it is aimed at by the European Water Framework Directive. The development process, which resulted in the release of the OpenMI is summarized in chapter 2. An introduction to the objectives, the concept and the technology of the OpenMI is given in chapter 3. Chapter 4 lists case studies in which the OpenMI has been applied. In Appendix B, each of the reported studies has been described in generalized form. A matrix showing all model links, which have been established within the case studies, has been developed. Finally, in chapter 5, an overview on other model linking approaches is given. This report shows that in many use cases the Open Modelling Interface could be used successfully for model linking. Even out of Europe, at a workshop of the U.S. EPA it is stated that, in terms of the ability to go between different temporal and spatial scales, a framework such as OpenMI might have the necessary flexibility. Actually, it was found that in many cases models of the InfoWorks software family have been part of the OpenMI linked systems. In cases of many interaction points between models, the OpenMI mechanism may not be applicable. In the Berlin case the impact of combined sewer overflows on the water quality of the receiving river shall be examined. With far less than a hundred interaction points between sewer model and river model it is assumed that the OpenMI could be used for a successful model linking. The difficulty within the SAM-CSO project may be to find an apropriate river quality model, which is ready to be linked to InfoWorks CS using the OpenMI. Unfortunately, there are few use cases reported in which a freely available river water quality model was involved. The water quality model QSIM of the German Institute of Hydrology (BfG) that is used within the project is currently not equipped with OpenMI. Nevertheless, using the OpenMI mechanism for model linking is assumed to be a promising approach. It is expected to become an internationally accepted standard. As the OpenMI specification is fully free, anyone may contribute to its further development. The OpenMI Association will give advice to modellers and will be open to discussions on improvement of the OpenMI. With the OpenMI linking mechanism not only models can be linked. Modules for calibration, optimization, statistical evaluation etc. can be part of an OpenMI system as well as components for generic data access or visualization. It will be tested, if the integration of such a module for statistical evaluation into the CSO impact assessment method (to be developed within the project SAM-CSO) is applicable and useful.

The importance of integrated modelling of urban wastewater systems is ever increasing, also due to the European Water Framework Directive. In order to facilitate its practical application, the Central European Simulation Research Group (HSG) has prepared a guideline document, suggesting a seven-step procedure to integrated modelling. Findings of recent research and application projects in Central Europe have been integrated in the guideline. The present paper outlines this guideline document. The full guideline will be made available on the Internet.