RANKING STRATEGIES FOR STORMWATER MANAGEMENT UNDER UNCERTAINTY - SENSITIVITY ANALYSIS

The disadvantageous consequences of stormwater perturbations of receiv ing water quality in urban environments can be attenuated by exercisin g control at various locations across the sewer network, wastewater tr eatment plant, and the stream itself. As part of a long-standing progr amme of research on developing an integrated approach to the managemen t and real-time control of water quality in river basins, the paper ex amines the sensitivity of the associated strategies to model uncertain ty. Specifically, results are presented for a case study based on a 10 km stretch of the River Cam as it passes through the city of Cambridge in eastern England. The options for control are restricted to design and operational features of the wastewater treatment facility. Assessm ent is according to maximum and cumulative values of mass flows of amm onium-N and biochemical oxygen demand, together with the duration of d issolved oxygen concentration below 4.0 gm(-3), at the downstream boun dary of the system. A straightforward analysis of the sensitivity of t hese criteria to changes in the parameterisation of a model for receiv ing water quality shows that the ranking of strategies is robust in th e face of model uncertainty. Minor differences in ranking occur as a f unction of whether judgement is based on ammonium-N or the other two a ttributes of water quality and whether attention is focused on the tre atment plant in isolation or performance across the system as a whole. However, such conclusions must be qualified by noting that our analys is has been limited in its scope and elementary in its treatment of un certainty. (C) 1997 IAWQ. Published by Elsevier Science Ltd.