IIRC, some substantial construction on new reservoirs did happen recently, after a long—heh—drought.

goes looking

premierconstructionnews.com/…/holcim-uk-awarded-s…

Holcim UK Awarded Supply Contract for UK’s First Reservoir in Over 30 Years

Holcim UK is delighted to announce its appointment by Future Water MJJV Ltd to supply essential materials for the construction of the UK’s first reservoir in over 30 years – Portsmouth Waters’ Havant Thicket reservoir. The reservoir is an environmentally-led project that will help to safeguard internationally rare chalk rivers in Hampshire by providing an alternative, sustainable source of water.

The reservoir, which is being delivered by Future Water MJJV Ltd, a joint venture between Jones Bros Civil Engineering UK and JT Mackley & Co Ltd, is expected to be completed by the early 2030s. It is estimated to take approximately three years to fill and will have the capacity to hold up to 8.7 billion litres of water, playing a crucial role in enhancing water security for the region.

gov.uk/…/government-steps-in-to-build-first-major…

Government steps in to build first major reservoirs in 30 years

New reservoirs will supply three quarters of a million homes and unlock the building of tens of thousands more as part of the Plan for Change