In the first week of August 2026, water scarcity was reported across the trade press as a new barrier to the government's housebuilding targets. The figure attached to it was 61,600 homes.
The figure is real and the problem is serious. The research behind it was published on 29 January 2025.
Where the number comes from.
The Chartered Institution of Water and Environmental Management commissioned the policy consultancy Public First to model what water availability does to housing delivery, as part of its Enabling Water Smart Communities work. The findings were published on 29 January 2025.
The modelling found that water scarcity could prevent roughly 61,600 homes being built in the East and South East of England over the following parliamentary term, which is close to 40% of the additional housing those two regions need to meet their targets. It put the economic cost of the undelivered housing at around £25 billion.
Those are the numbers being quoted now. They are eighteen months old.
Why the age of it matters.
This is not a complaint about the research, which is careful and clearly dated by the people who did it. It is about what has happened to the number since.
A number does not become current by being repeated. It becomes older, while sounding newer each time.— The Editor · Ground Level, August 2026
A projection of what might happen over a parliamentary term, published in January 2025, is a different thing from a statement about where housing delivery stands in August 2026. Some of the period it modelled has now happened. Whether the constraint bit as hard as forecast, harder, or less hard is a question the original study cannot answer, because it was written before the answer existed.
This publication has just spent a fortnight correcting its own back catalogue for the same failure. A five year housing land supply figure from November 2025 and a housing need figure from December 2024 were both stated in the present tense long after the council had moved on. The correction notes are at the foot of the pieces concerned. It would be poor practice to fix that and then repeat it with somebody else's number.
So the honest position is this. The 61,600 is the best published figure available. It describes a projection made in January 2025. Anyone quoting it in 2026, including us, should say so.
What is not in doubt.
The underlying constraint is real and there is current evidence for it that does not depend on the modelling.
Cambridge is the clearest case and our infrastructure explainer set it out. The Environment Agency objected to housing schemes in 2022 and 2023 on the grounds that abstraction from the chalk aquifer was already damaging water bodies, and around 9,000 homes were effectively frozen. On 9 October 2025 Cambridge City Council passed a motion recording that the government's refusal to fund relocation of the waste water treatment plant at North East Cambridge would block at least 5,600 homes. The same motion noted that Anglian Water had objected to several planning applications in Cambridge on the grounds of a lack of waste water treatment capacity. Water stress in Cambridgeshire has also held back around 300,000 square metres of commercial development.
Sewerage is a separate constraint with the same effect. The Home Builders Federation documented at least 30,000 homes stalled across England in September 2025 because water companies could not accept the flows, of which an estimated 18,000 sat behind a single sewage works at Oxford.
And the August 2026 position is odd on its own terms. The Planning Portal reported on 6 August 2026 that applications submitted in England in the 12 months to June 2026 proposed 412,130 homes, a five year high. The same bulletin reported Rightmove's finding that the number of new-build developments coming to market had fallen to its lowest level in more than a decade. Applications are a measure of intent. Developments reaching the market are closer to a measure of what the ground can actually take.
The part that makes this a planning story.
The mechanism is the same one this publication keeps finding, and it is worth stating plainly because it explains why water arrives as a surprise.
A council's housing target is produced by the standard method: 0.8% of existing dwelling stock, multiplied by an adjustment derived from the ratio of house prices to local workplace earnings. There is no water term in that calculation. There is no sewerage term, no aquifer, no abstraction licence and no treatment capacity.
Water enters the system much later, as an objection to an individual planning application, by which point the number has been set, the local plan has allocated, and the council is being measured against a total it may not be able to deliver.
That is the same shape as the infrastructure problem generally. What makes water different is that it is the one constraint that cannot be negotiated away with a contribution. A junction can be upgraded and a school extended if somebody pays. An aquifer cannot be topped up. Under section 106 of the Water Industry Act 1991, and confirmed by the Supreme Court in Barratt Homes v Dwr Cymru in 2009, a water company cannot refuse a connection on grounds of inadequate capacity. So the legal right to connect and the physical ability to serve have come apart, and neither the developer nor the undertaker has the incentive to close the gap before the houses arrive.
The local version.
The Lechlade application this publication has been following is the same gate at field scale.
Natural England wrote to Cotswold District Council on 25 March 2026 saying it needed further information on the impact on the Cotswold Water Park Site of Special Scientific Interest, on groundwater, on foul drainage and on wintering birds, and that without that information it may need to object. As at 7 August 2026 it had issued nothing since. Thames Water commented on 10 July 2026. The application remains undetermined, four months past its own target date.
Harm to a protected site is not weighed against housing need in the ordinary way and outweighed by it. It behaves more like a gate. That is why the water and drainage points in that file matter more than the landscape ones, and it is the practical lesson for any parish looking at a scheme near a designated site.
What would actually answer this.
Two things, and one of them is a policy question rather than an engineering one.
The first is whether the standard method should carry a physical constraint at all. It does not. The December 2024 framework removed the clause, at paragraph 61 of the December 2023 version, that allowed an alternative approach to assessing need where exceptional circumstances such as an area's demographic characteristics justified it. That clause was about demographics, not capacity. The capacity route survived elsewhere. Paragraph 11(b)(i) of the December 2024 framework let a plan provide for less than its need where policies protecting areas or assets listed in footnote 7, such as National Landscapes, habitats sites and land at risk of flooding, gave a strong reason, and paragraph 69 set the housing requirement at the extent to which need can be met. Water supply is not on the footnote 7 list. It is the strongest case anyone could make for adding it, because it is the one constraint that cannot be bought.
The second is whether the Environmental Delivery Plans created by the Planning and Infrastructure Act 2025 will do for water what they are meant to do for nutrients. Natural England notified the Secretary of State in December 2025 of its intention to prepare 23 such plans, 16 of them addressing nutrient pollution, with the first consultations due during 2026. Pooled mitigation at catchment scale is the right shape of answer. Whether it delivers is the same question this publication has asked of every pooled mechanism since the Community Infrastructure Levy. Money is collected reliably. Delivery is harder to observe.
If you see 61,600 quoted anywhere this autumn, it is the January 2025 figure. There is not a newer one.