Long-Term Projections of Domestic Water Demand: A Case Study of London and the Thames Valley

This case study implements long-term projections of domestic water demand for a UK water company, Thames Water. Projections of per household consumption (PHC) and households were combined to yield future demand. Regression models predicted PHC using the determinants of occupancy, property type, ethnicity and rateable value, drawing on 2006–2015 domestic water-use data as a baseline. A model was developed for diffusing savings in per capita consumption (PCC), drawn from published studies of interventions. PCC declines were converted to PHC reductions using baseline ratios. Interventions were grouped into Business as Usual, Light Green (limited intervention), and Dark Green (extreme intervention) scenarios. Projected households were generated by property type, occupancy, and ethnicity for Thames Water’s resource zones for 2011 to 2101 and multiplied by projected PHCs to yield water-demand projections. By 2101, the 2011 water demand of 1,225 million liters a day grew 90% under Business as Usual, 69% under Light Green, and 46% under Dark Green.