Integrated modelling of urban watercourses

Abstract

The paper describes an integrated modelling study that was undertaken as part of the investigations into improving the performance of the urban wastewater system of Belfast, Northern Ireland. The objective of the study was to assess the impact of the combined sewer overflow (CSO) discharges from the current and proposed upgraded sewer system on the major receiving water-courses in the Belfast urban area. The study employed the methodology of the Urban Pollution Management Manual, 2nd edition, implemented through simplified integrated urban wastewater modelling tools to assess the impacts of the CSO discharges on both inland and tidal receiving waters. The Blackstaff River is predicted to achieve its long-term water quality objective if the proposed sewerage upgrading scheme is implemented and the quality of the upstream tributaries is improved. The proposed sewer upgrading will cause a significant improvement in dissolved oxygen levels throughout the Lagan impoundment. This should allow the impoundment to achieve its environmental quality objectives. The overall study concluded that the proposed sewer upgrading scheme will allow the long-term environmental objectives for both the Blackstaff and the Lagan to be achieved, provided improvements to other sources of pollution are also addressed. The study demonstrated that the methodology employed is suitable for the investigation of large and complex systems where limited data are available.