Evidence Base for Large-scale Water Efficiency: Phase II Interim Report

Several regions of the UK are already under serious water stress as a result of increasing population density, demographic change, increasing demand due to more intensive lifestyles and a climate in which extreme rainfall events and drought are becoming more and more prevalent. Future climate scenarios and population predictions suggest that more areas will be affected in the future.

In the past, there has been a perception in the water industry that there is insufficient evidence in the UK of the ability of water efficiency to deliver water savings cost-effective enough for it to be able to play its part in a twin track approach to water resource management, in which it contributes as a demand management measure alongside supply-side resource measures. In Ofwat’s final determination for PR09, six water companies in England and Wales were awarded funding for largescale water efficiency programmes.

This shows that water efficiency does have an important role to play in helping the UK to meet these challenges. The Evidence Base represents the best current available knowledge of water efficiency in the UK. This report does the following:

  • Presents the robust, measured water savings from water efficiency trials and projects in the UK
  • Explicitly details the uncertainty in the results and reveals structure in the distribution of water savings
  • Presents the typical costs involved in each trial
  • Develops a set of scenarios for large-scale water efficiency programmes, which include water savings, Average Incremental Cost (AIC) and Average Incremental Social Cost (AISC).
  • Compares measured water savings to theoretical water savings to direct future savings estimates for water savings measures
  • Estimates carbon emissions and energy savings for each trial
  • Makes recommendations for further work for the Evidence Base and for key stakeholder group


Ike Omambala et al


9 February 2010


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