Water resource management can be summed up in three words: “we don’t know”. The nature of the problem is that water is part of a natural cycle, so managing water resources is a process of managing risk. These words are being written at the end of May 2025 following the lowest Spring rainfall in the south-west UK for eighty years, but we don’t know what will happen next – precise weather forecasting more than 3 months into the future will always be impossible because the “butterfly effect” kicks in and the tiniest change in starting conditions can transform the outcome a few months later. So, readers of this article may know whether the UK suffered a drought in 2025, but the writer cannot.
Even after the event when you have the data, “a drought” is not a single or easily defined thing – environmental drought may affect river flow or ecology but not have much impact on farming; agricultural drought could affect crop yields but is very season-specific; groundwater drought might be something that develops over a period of four or five dry winters that most people barely notice. Then there’s water supply drought, which has been the focus of much of my career.
We tend to think about water supply in the same way that we think about air: we don’t think about it at all until we lose access to it, at which point it gets our undivided attention. But if the water supply system ever breaks down due to drought, it can really break. A hose ban is one thing, but standpipes in the street are quite another. The worst kind of breakage – the one to be avoided no matter what – is when the water supply simply stops. Unlike other essential services where it’s possible to implement some kind of backup – for instance, energy or telecoms – if you run out of water, it can stay that way for a long time because for every million people you supply, you will need a million tonnes of water per week. That’s too much of anything to just go and fetch, so if the worst ever happens it might just be too late to fix.
If you ask a member of the public whether the UK is a wet country, they will laugh at you – the answer is yes, of course; it’s our national joke. But the UK climate is actually rather special in global terms. No hot season, no dry season, no cold season, no wet season – just a gentle pattern of consistent and modest rainfall throughout a cool and rather cloudy year, and not unusual to get a day in July where the temperature is the same as a day in January. It’s relatively dry in global terms, but we have an ecology and a water supply infrastructure that relies on 50mm to 90mm of rainfall per month to keep ticking over properly. Essentially, we live on drizzle and hope it keeps coming.
But droughts can and do happen, so in the UK we create water resource management plans (WRMP) to cover a period of (at least) 25 years, and revisit them every five years. The plans target what’s needed to get through a record-breaking drought, and include “headroom” for when things go wrong, with a range of options to manage water supply and demand, including smart metering, new sources, better treatment and cuts in leakage. This is called the supply/demand balance and it’s worked well so far – we turn on the tap without a second’s thought, largely because every water supplier is working in the background, successfully operating an integrated supply network and keeping a diverse range of water sources running so that not all the eggs stay in one basket.
Yet the world is changing. UK rivers are short, so they drain quickly (unless, like our beloved chalk streams, they are fed by groundwater), and climate modelling indicates that in the south west by 2050, the Q99 flow (the flow exceeded 99% of the time) on some watercourses could hit zero, even on some watercourses where there is no abstraction at all. Rivers that have flowed since the last ice age could, in some future summers, just dry up. No fish, no macrophytes. This is a tragedy in its own right, but there’s also quite a frightening potential implication for water supply, because in an emergency, there would simply be no water to be had.
The focus for water resource management over the last thirty-five years has been on finding new and better ways to reduce demand, and I’m proud to have been part of this. Since I joined the industry in 1990, leakage has been cut by a third (or maybe more: leakage assessments in 1990 had some questionable assumptions, but we now have continuous monitoring and leakage alerts across entire networks). The easy wins on leakage are probably gone: high leakage areas have been located and addressed; pressure management has been installed so now we are shifting to more costly remedies such as area-wide mains replacement, but per capita consumption continues to fall with increased meter penetration and public awareness. Smart metering is bringing new ways to use big data sets to understand how things may change in the future, and the increased environmental stewardship ethos I have seen develop in the water industry and our wider society fills me with real hope for the future.
But demand reduction is only one side of the equation and I’ve come to realise that the next logical step in water resource management is surprisingly simple. Storage. Reservoir assets can last over a thousand years (the oldest known reservoir, Lake Homs in Syria, is said to be over 3,000 years old)1 and with stored water available, it’s still there waiting for you if it takes longer than expected to get everything working when drought strikes. Reservoirs are expensive, however, and they take up land, so since privatisation it’s been easier to defer and delay this infrastructure investment (the regulators’ term for “no”, is “we need more robust evidence”) rather than take the leap.
It is also very difficult in a small and relatively crowded island like the UK to find somewhere to put a reservoir. If it is sited at the top of a catchment it will be supplied by small watercourses so it will fill slowly (or require a pumped storage system), and it will have a significant impact on the downstream watercourse simply because it’s at the start of the river – and if this kind of location is also in an unpopulated area, it’s quite likely in a “wild” environment where ecological considerations are hugely important. Conversely, if a reservoir is sited towards the bottom of a catchment area, water quality may be poor, making it more costly to treat and it will almost certainly be in a populated area where people affected will have very strong opinions indeed about their home being in the footprint of a new reservoir.
Thankfully, these problems are at last starting to be solved. Although the newest reservoir in the UK (Carsington Water in Derbyshire) is now 33 years old, the case for more reservoir storage has finally been accepted by our government and schemes are in development – small ones at first, though a large proposed reservoir for the London area is making progress at last.
One of the most interesting is perhaps the Mendip Quarries reservoir scheme, which plans to take a superquarry due to be decommissioned in 2040, and repurpose this as a reservoir. The fundamental advantage with this scheme is that much of the construction has already been done, but there will be other opportunities out there which may be just as promising and we need to continue these investigations.
There will be challenges, and changes to our approach will be needed, but if we want a water supply system that remains resilient to a climate that’s changing in front of our eyes we will need to invest in infrastructure – and we will need to store water.
Patric Bulmer has been involved in the UK water industry for over thirty years, and was until 2024 the Head of Water Resource and Environment at Bristol Water. He now works as an independent consultant.
FWR Analysis Articles are designed to provide a view on topical issues across the water sector. This is an opinion article and does not necessarily reflect the views of the FWR, IES or the author’s current or past affiliated organisations.
Featured header image: Normanton Church visible over the reservoir at Rutland Water Nature Reserve © Matthew | Adobe Stock
- There is some debate over the Lake’s exact age, while sources state that the dam was built in 284 AD by the Romans, there are claims that the original reservoir dates back to the Ancient Egyptians under Pharaoh Sethi. ↩︎
