Question to the Department for Environment, Food and Rural Affairs:

To ask the Secretary of State for Environment, Food and Rural Affairs, whether his Department uses sewage to estimate population changes.

Defra does not routinely measure population changes and therefore does not use sewage monitoring for this purpose.

Sewerage undertakers account for population changes in their business planning by using local Government growth plans and population data supplied by the Office of National Statistics.

Sewerage undertakers use projections of population growth at a sewerage catchment level to assess future capacity needs within their Drainage and Wastewater Management Plans (DWMP). Since 1 September 2024, sewerage undertakers in England are required to prepare, publish and maintain a DWMP. The DWMP is a key evidence base to inform future capacity needs in the sewerage undertakers' business plans.