Water Science & Technology Vol 66 No 2 pp 304313 © IWA Publishing 2012 doi:10.2166/wst.2012.178
Water quality-based assessment of urban drainage impacts in Europe – where do we stand today?
F. Blumensaat, P. Staufer, S. Heusch, F. Reußner, M. Schütze, S. Seiffert, G. Gruber, M. Zawilski and J. Rieckermann
Technische Universität Dresden, D-01062 Dresden, Germany E-mail: firstname.lastname@example.org
Eawag, Swiss Federal Institute of Aquatic Science and Technology, CH-8600 Dübendorf, Switzerland
TU Darmstadt, Darmstadt, Germany
ifak, D-39106 Magdeburg, Germany
CRP Henri Tudor, L-1855 Luxembourg-Kirchberg, Luxemburg
Institute of Urban Water Management and Landscape Water Engineering, Graz University of Technology, A-8010 Graz, Austria
Lodz Polytechnical University, PL-90-924 Lodz,Poland *HSG group – Central European Simulation Research Group (HSG) (www.hsgsim.org)
Traditionally, design and optimisation of urban drainage systems was mainly driven by cost efficiency, surface flood prevention, and later by emission reduction. More recent procedures explicitly include ecological conditions of the receiving water in the definition of acceptable pollutant discharges via sewer system and treatment plant outlets. An ambient Water Quality based impact Assessment (WQA) principle therefore requires an integrative system optimisation. However, a broad range of mostly national WQA protocols exist across Europe varying in structure and complexity, assessment concept, spatial and temporal scope and handling of uncertainty. This variety inherently implies a considerable risk of subjectivity in the impact assessment with highly variable outcomes. The present review identifies differences and similarities of WQA protocols in use and discusses their strengths and weaknesses through: (i) a systematic comparison of WQA protocols by selected attributes, (ii) a review of real-life cases reported in the literature and expert interviews, and (iii) an illustration of our main findings by applying selected WQA in an instructive example. The review discusses differences in structure and concept, which are mainly identified for simplistic WQA protocols. The application of selected protocols to an example case shows a wide variety of numerical results and conclusive decisions. It is found that existing protocols target different questions within the decision making process, which users should be more aware of. Generally, to make assessments more reliable, further fundamental research is required to fully understand the relationship between stressors and stream ecosystem responses which will make assessments more reliable. Technically, tools suggested in WQA protocols show severe deficiencies and an uncertainty assessment should be mandatory.
Keywords: decision making; integrated urban water management; receiving water quality; uncertainty analysis; water quality-based impact assessment
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