London water supply infrastructure

London's water supply infrastructure has developed over the centuries in line with the expansion of London.

Beginning in the 16th century, private companies supplied fresh water to parts of London from wells, the River Thames and the River Lea. Further demand prompted new sources, particularly when the Agricultural and Industrial Revolution caused a boom in London's population and industry.

A crisis point was reached in the mid 19th century with the discovery that cholera arose from the extraction of water from the increasingly polluted Thames. The Metropolis Water Act 1852 banned this practice, allowing water companies three years to find other sources, but issues with contaminated water persisted. In 1904, London's water suppliers were taken into municipal ownership as the Metropolitan Water Board, which substantially upgraded the water infrastructure, building many new reservoirs. Ownership subsequently passed to the Thames Water Authority, before being re-privatised in the 1980s.

Today, the population of Greater London is supplied by four private companies: Thames Water (76% of population), Affinity Water (14%), Essex and Suffolk Water (6.6%) and SES Water (3.7%).^[1] The London area is classified as "seriously water stressed",^[2] receiving less rain than Rome, Dallas, or Sydney,^[3] and continued investment will be required to counteract the effects of climate change and a growing population in the 21st century.^[4]

Most of London's water is now supplied from five large water treatment works fed from the Thames and Lea, and to a lesser extent from aquifers and a desalination plant at Beckton. As of 2020,^[update] Thames Water's London zone, which serves the majority of London's water users, has the capacity to supply 2.3 gigalitres (510 million imperial gallons) of water per day.^[5]