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Integrated Water Cycle Management and sewerage planning

12th May 2017

As the water industry moves towards Integrated Water Cycle Management (IWCM), this article looks at the level of integration of water resource and sewerage planning. With water companies currently concentrating on the delivery of water resource management plans (WRMP) for the next 25 years, this raises the question: how are sewerage services planned to reach a fully integrated water cycle management of water supply and sewerage services?

The need to plan sewerage services is driven from Section 94 of the Water Industry Act 1991. This puts a duty on wastewater businesses “to provide, improve and extend such a system of public sewers (whether inside its area or elsewhere) and so to cleanse and maintain those sewers and any lateral drains which belong to or vest in the undertaker as to ensure that that area is and continues to be effectually drained”. Therefore, the objective of sewerage planning is to identify the investment needs of the sewerage system in an integrated manner and hence fulfil this duty.

However, there remains an absence of any statutory requirement for wastewater businesses to undertake sewerage planning in the same regulatory way as the WRMP process. Wastewater businesses employ a range of different methods to plan sewerage investment over short, long and strategic periods. These methods include Drainage Area Plans (DAPs), Drainage Area Studies (DASs), and Sewerage Management Plans (SMPs). These activities address key issues and cover operational, structural and hydraulic needs. There is even reasonable alignment between the data sets required by both WRMPs and sewerage plans. For instance, supply and demand forecasts and balances are similar in nature, and the external macro influences on development such as population growth, resilience, environmental pressures, and economics apply equally to water supply and sewerage demands.

One issue that requires key attention in sewerage planning is climate change. This is critical in achieving a successful IWCM outcome in the future. With increasing water supply demand - hotter summers and lower rainfall - summer river flows are likely to decrease at a key time when receiving water courses need to meet their full recreational potential and sewage discharge dilution is limited. This will drive even tighter consent limits and hence further treatment and the limited use of or removal of combined sewer overflows.

So what is happening? Well, something, but perhaps not quite enough to say it is going to be sorted soon!

There has been a review of sewerage planning and drainage area plans undertaken by Atkins, and driven by Ofwat in 2011, and more recently Water UK has launched its 21st Century Drainage Programme. But there is little evidence freely available to suggest that integrated thinking and management will happen soon. There has been much said in the environment press over the last 5-10 years about catchment management and working with farmers in supporting the catchment based approach (CaBA). But this alone is not IWCM. True IWCM is about the interaction of water, wastewater, the environment and society across the whole water cycle. To address these issues regulation alone will not succeed. Changes in culture and business approach are required as a wider suite of challenges and complex issues are addressed. Thomson Ecology are leaders in the field of understanding the relationship between ecology and water and have a team of forward-thinking consultants that are dedicated to seeing IWCM support the needs of the environment and society over future years.

This is the second in a monthly series of water articles by Dr Phil Aldous, Director Water at Thomson Ecology. To speak to Phil directly, you can call him on 01483 466000 or email him on enquiries@thomsonecology.com


Image: courtesy of Bazalgette Tunnel Limited

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