Image by Chris Montgomery


Client: Dwr Cymru Welsh Water


Dwr Cymru Welsh Water (DCWW) supplies drinking water and wastewater services to approximately 1.4 million homes, 3.1 million people, in Wales and the border locations of England. Annually, DCWW is required to report on the size of its ‘usually resident’ population and to indicate the likely scale of any hidden & transient populations (excluded from the published usually resident total).  Hidden and transient populations can have both a permanent and/or seasonal impact, the latter relating to tourist populations in particular.

The COVID-19 pandemic has had a profound effect on all aspects of UK society, altering individual and household behaviours and the normal operation of all aspects of the UK economy. The social and economic disruption has resulted in important changes to the UK’s hidden and transient populations, with changes to the arrival of short-term residents, the use of second homes, the mobility of domestic visitors, plus the constraints on international arrivals and departures.

To reflect this, DCWW commissioned Edge Analytics to provide updated hidden and transient population estimates for its area of operation, taking account of the latest available evidence and considering the impact of the easing of COVID-19 restrictions upon hidden and transient populations. In particular, DCWW sought to understand the impact on domestics tourism to Wales, in light of the domestic restrictions easing, plus the continued constraints on international travel.


Edge Analytics used its Hidden & Transient Population Model to estimate population totals in each Water Resource Zone and Wastewater Zone, taking account of specific hidden and transient sub-groups: Irregular Migrants, Short-term Residents, Second Address Residents, Domestic Day Visitors, Domestic Night Visitors, and Foreign Night Visitors.

Evidence was drawn from published research and reports, the latest statistical releases from Welsh Government, Office for National Statistics and the Department for Works and Pensions, plus survey evidence on accommodation occupancy and domestic tourism trends. 

Benchmarked against a ‘normal’ year, the analysis derived hidden and transient estimates, adjusted in line with the latest evidence on the impact of COVID-19. Monthly estimates were derived for 2020 and 2021, providing seasonality profiles for each population, reflecting the phases of COVID-19 restrictions.

A Final Report, accompanied by key datasets and associated visualisation, provided the basis for the formal consideration of hidden and transient populations in providing for water and waste services within DCWW’s mandated business planning process.