Locale : Global (English)
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An aerial view of the Thames Valley water works in London

Thirsty work

Thames Water in the south east of England provides water and sewerage services for over a quarter of the UK’s population.

ClientThames Water
ExpertiseStrategic planning, option appraisal and stakeholder engagement


As with many utilities worldwide, Thames Water faces a considerable present and future challenge to secure water supplies for its customers.

Not only will Greater London’s population grow from 8M to 11M by 2050, but climate change will likely bring drier summers and wetter winters, providing less resource when it’s needed most and greater chance of flooding. If left unchecked, current forecasts predict a potential resource deficit of over 400Ml/d in London by 2040, equivalent to the water needed by around 2M people, and 800Ml/d by 2100. Thames Water required a long-term strategy, supported by the many interested stakeholders, to manage demand and, where appropriate, develop major new resources to secure supplies for London and the Thames Valley into the future.


We supported Thames Water in developing its water resource management plan for London with a 2100 planning horizon. We engaged collaboratively with stakeholders from the outset through regular technical groups and forums, to identify options, develop the methodology for options assessment and discuss the outcomes of the options screening process. At each stage, we requested and incorporated, or responded to, stakeholder feedback.

Our water resource planning experts investigated a wide range of options to strengthen the long-term resilience of Thames Water’s supplies, including:
• augmenting raw water resources with wastewater reuse
• reservoir development
• raw water transfers from other catchments such as the River Severn
• desalination
• groundwater development

We developed a three stage process to identify specific options for each resource type and to test the feasibility of each one, followed by a fine screening assessment where resource options of all types were compared. In all, more than 150 specific options were assessed. This enabled us to focus in on a ‘constrained list’ of around 40 options. Some of these could individually provide between 50Ml/d and 300Ml/d of additional water resource.

Integrating new and existing resources and assets efficiently, and at an affordable cost, were key considerations. To help, we developed an ‘elemental’ system to assist with the visualisation of how old and new would interact. This modular approach created elements for:
• treated water or augmented raw water supplies
• raw water conveyance
• raw water system reinforcement
• additional water treatment capacity
• treated water network reinforcement, including reinforcements to the London ring main

For each element we prepared conceptual designs, cost estimates and risk assessments that fed into Thames Water’s programme appraisal to identify the best value programme over the long term. The outcome from the water resources plan is a coherent action plan. It integrates options to manage demand, control leakage, develop new resources and reinforce the system. The strategy is underpinned with robust evidence and has been developed in close consultation with stakeholders throughout.

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