The demand for water in the UK is ever increasing and it has been forecast that in the not-too-distant future, demand will outstrip supply. In this two part article, I examine the reality behind the government’s plans to prevent the country running dry. Part one examines current capacity, projected demand and the constraints water companies face. Part two considers whether new reservoirs, storage facilities and desalination plants can meet the needs of a growing population, a shrinking area of land from which to draw water, and newly emerging sources of demand.
This analysis is based on the best publicly available data, interpreted by an informed lay observer rather than a specialist in the water sector. Its aim is to highlight some of the complexities facing decision-makers in the water sector and government as demand continues to rise.
Housing targets and water demand
In December 2024, then Prime Minister Sir Keir Starmer’s Plan for Change committed to delivering 1.5 million new homes in England by the next general election, due no later than 15 August 2029. In the period 2000-2025, over 3.75 million new homes have been built and if including net additional dwellings, that figure adjusts to 4.75 million. Whether a further 1.5 million homes represents a sustainable response to demand, or simply defers the same question to the next parliament, is one decision-makers will need to confront.
Centrally determined, formulaic housebuilding targets uniformly applied under successive governments regardless of price or location have contributed to decimation of vast swathes of the British countryside. What happens when the current target of 1.5 million new homes is met remains an open question; it seems reasonable to assume it will be followed by another.
Population and water consumption
England’s population in the middle of 2025 reached 58,834,800, according to the Office for National Statistics (ONS). At the time of writing, an error in the ONS’s subnational projections meant a corresponding population projection could not be drawn. However, the UK population is projected to grow, driven mainly by net migration – the balance between arrivals (on work, study and family visas, alongside returning UK citizens, resettled refugees and those granted asylum) and departures. Asylum seekers granted UK residency form a comparatively small part of the total – just under 250,000 according tothe House of Commons Library.
Water UK states that the average person uses 137 litres of water a day equating to slightly over 50cubic metres each year. Applied to England’s current population, this adds up to approximately 2.94 billion cubic metres of water annually.
Using the standard average of 2.36 people per household, 1.5 million new homes would house roughly 3.5 million additional people, requiring a further 177 million cubic metres water each year. This converts to a projected annual demand of approximately 3.12 billion cubic metres – a figure that does not take into account the demand for water that industry, infrastructure and the services of these new houses will need, and takes no account of the additional hard-standing that will reduce the amount of rainwater able to percolate into the ground and ultimately reach reservoirs.
Current storage capacity
Responding to a question from Tim Farron MP, the water minister Emma Hardy confirmed that the Environment Agency’s National System Simulation Model, which covers 90% of England’s supply system, shows the current national total storage capacity at 2.03 billion cubic metres for public water use. Set against projected demand of around 3.12 billion cubic metres, this points to a substantial and growing shortfall.
But storage is only one part of the water management cycle. There are also inputs, processing, distribution, wastewater treatment and clean discharge. The last of these is a persistent weak point, given the continued discharge of sewage into rivers and coastal waters.
Catchment areas and effective rainfall
Reservoirs are replenished by rainfall that either percolates into the ground or runs into streams and rivers within their catchment areas. The Environment Agency defines “effective rainfall” as rainfall available to percolate into the soil or produce river flow. The size of a catchment area therefore affects how quickly a reservoir will fill.
Runoff from hard-standing areas does not flow directly into reservoirs, but via ageing infrastructure and routes about which there’s little accurate information – local authority roads, ditches, streams and so on – before finally reaching the reservoir. Pollutants may get added in some of these, or filtered out to some degree in others. Currently, nobody really knows which will predominate. Improved digital mapping should, in time, clarify both what goes where as well as what happens to it on the way.
Future pressures
The Environment Agency has estimated a shortfall of nearly five billion litres of water a day by 2050 – equivalent to more than a third of the current water supply. Beyond housing, further demand will come from industry, businesses, agriculture and, increasingly and controversially, data centres. We don’t necessarily know how much this will add up to.
Reliable data on agricultural water use is scarce. A 2018 freedom of information request to the ONS for total agricultural water consumption over the preceding five years returned the response that the ONS does not hold this information, and no more current figures could be located.
A major unknown is the future water demand from data centres, particularly as the rapid expansion of AI drives demand. A recent UK government report on water use in data centres suggested this demand could be substantial. This could place significant additional pressure on local water supplies, particularly in areas already vulnerable to drought.
The scene is set
Taken together, the picture is one of a rising population and housing targets, several significant water-using sectors whose consumption is poorly recorded – or not yet known – a shrinking area of land able to generate effective rainfall, an increasingly unpredictable climate in which intense rainfall on dry, hard ground produces rapid runoff rather than absorption, and fast-emerging demand from data centres. In part two, I examine whether new reservoirs, storage facilities and desalination plants can realistically be expected to close this gap.
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