London, built astride the River Thames and under the tidal influence of the North Sea, is expected to keep growing from the present day population of 8.6 million to 10 million by 2031xxxviii. It is located in the most populated and driest part of the United Kingdom – an area classified by the UK Environment Agency as being ‘severely’ water stressed. One of the city’s main concerns is maintaining a secure and sustainable supply of fresh water, especially as Thames Water, the main water utility for London, estimates that without action, demand for water will exceed supply by 213 million litres of water per day by 2025xxxix. This deficit reflects a combination of the expected increasing demand for water from a growing population, the projected decreasing availability of rainfall in warmer, drier summers due to climate change, and need to integrate the European legislative requirement to protect unsustainable water abstractions. The city government is working closely with Thames Water on a twin-track programme to balance supply and demand for water through improving the water efficiency of existing properties while seeking new climate-resilient water resources.


The aim of achieving greater water security will be met through a combination of actions. Firstly by reducing the demand for water through fixing leaks in the main water distribution networks, ensuring new development is water efficient, and implementing an integrated programme of retrofitting water efficient devices, installing smart water meters and raising awareness of the financial and environmental benefits of being more water efficient to encourage behaviour change among consumers. In parallel, Thames Water is working to understand the resilience of new water supply options to long-term future challenges. This involves modelling how well individual and combinations of water supply options (for example a new reservoir, desalination, etc.) respond to future challenges despite deep uncertainties about the impact of climate change, energy costs, population growth, etc. The aim is to develop an optimised portfolio of water supply options that provides the greatest resilience and environmental benefits for the best value.

Reasons for success

London recognised the economic and environmental benefits of saving water resources and implemented its household water efficiency retrofits based on a detailed cost-benefit analysis. The city also explores partnerships with a number of stakeholders, from water utility to energy efficiency service providers, to help share the efficiency retrofits’ cost. 

C40 Good Practice Guides

C40's Good Practice Guides offer mayors and urban policymakers roadmaps for tackling climate change, reducing climate risk and encouraging sustainable urban development. With 100 case studies taken from cities of every size, geography and stage of development around the world, the Good Practice Guides provide tangible examples of climate solutions that other cities can learn from. 

The Climate Change Adaptation in Delta Cities Good Practice Guide is available for download here.  The full collection of C40 Good Practice Guides is available for download here.  

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Key Impact
The City recognised the economic and environmental benefits of saving water resources and implemented its household water efficiency retrofits based on a detailed cost-benefit analysis
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