The Hydraulic Modelling of Sewerage Systems to Reduce Wet Weather Spillage

Melbourne Water have set a level of service for Melbourne's wastewater system - it shall contain all flows resulting from a 1 in 5 year storm without spilling to the environment. To achieve this, 18 000 kilometres of sewer will be assessed for its performance and where rehabilitation is required, the options investigated for their viability. The assessment, currently undertaken by Melbourne Water's Sewer Assets Team, involves the development of hydraulic models for relatively small sewer catchments. Local problems such as inflow and infiltration and undersized pipelines are determined and addressed. With the restriction on catchment size and the amount of flow monitoring undertaken, the models can be calibrated to accurately simulate the sewer system. In the past, rehabilitation works have been carried out on Melbourne's sewer system with little regard to their effects on connected pipelines primarily because the hydraulic tools were not available. Today, as well as being able to simulate flow characteristics within a sewer system, any works proposed for performance improvement can be investigated for their effectiveness on individual pipelines and on the integrated system.