Really great read. And whilst a hot topic, I didn’t see anything about data centres and their water usage; surely demand is going to rocket due to them too??
Much of southern and eastern England is indeed underlain by major Chalk *aquifers*, which is not quite the same as your chalk streams. The chalk acquifer for London is buried beneath impermeable London Clay & is recharged by rainfall on the downs & Chilterns... although this in turn sustains groundwater-fed chalk streams.
So regional water-supply system serving the South East draws heavily on groundwater resources that are hydraulically connected to sensitive rivers elsewhere. I see by chance that there is another Hannah Ritchie on LinkedIn “PhD | FGS | Hydrogeologist at Envireau”, who you might connect with on this!
Finally, is privatisation the cause, or a regulatory system that was focused on reducing consumer water bills at the expense of longer term investment? The lever was indirectly in the hand of government
Many thanks, Hannah, for another excellent piece with well-reasoned logic (and a few surprises!).
In addition to endorsing Akara’s pertinent comment about data centres, I would also highlight that reduction in consumption through efficient fittings and user behaviour offer real potential gains. And these are not just in water supply itself, but in associated processes such as purification, water heating, and drainage and waste treatment.
I’m unsure of the UK regulations for water-efficiency, but a few years ago in New Zealand I did an exercise on national shower usage (for a notional population of 5 million people). In summary, the widespread adoption of low-flow showers (say under 6 litres/minute) could potentially save the equivalent of a modest river flow of water (both freshwater and grey water) and a modest power station for water heating - all with commensurate financial savings.
Thank you, Hannah. This is a very useful reminder that water scarcity is not simply about how much rain falls, but whether we have the foresight to store, move, recycle and manage water for the future.
For me, the bigger leadership question is how we create water abundance for people, nature and prosperity before scarcity becomes crisis. 💧
Having a little personal knowledge of a reservoir that was completed in 90s/00s I was curious about the extent of the data on Wikipedia. The current list is from a report covering 90% of UK reserves, and my guess is there are at least a few more. One of the reasons reservoirs are no longer built is cost.. the area I know had gravel deposits which were sold to cover the costs (and more) up until that market crashed. Would be interesting to dig into this a bit more.. new reservoirs are very tricky for communities (it took 20 years for planning permission in the case I know of) so the picture isn't so simple. The bigger question is whether there will be enough catchment area and rainfall to fill new reservoirs.. let alone the existing ones. I've heard of data (but do not have it to hand) that suggests this may not be the case. Again, an interesting line of research...
Having now gone off and read up a little bit, it looks like it would need some improvements in the current tech in order to make this work. Apparently existing plants are not only pain to take offline and restart but they also have to run at maximum throughput. There is no way to throttle back the process.
Hopefully some bright people will come up with a better design eventually.
Thank you for this brilliant and well-reasoned analysis, Hannah. I particularly appreciated your clarity in showing that the core issue is seasonal precipitation imbalance rather than annual rainfall, as well as your pragmatic stance that we need both new storage and aggressive leak reduction.
Your point about Victorian achievements resonated with me. In Japan, historical records show that the monk Kukai led the massive restoration of the Manno Reservoir in 821, completing it in under three months through remarkable community mobilization and advanced civil engineering. While modern safety and regulatory contexts differ, it offers an inspiring historical reminder that overcoming planning inertia is possible.
To address local opposition and lengthy timelines, smart alternatives to massive new surface reservoirs might also help—such as riverbed dredging to expand channel retention, multi-functional retarding basins, and underground storage that upgrade existing infrastructure with minimal disruption.
Crucially, as you highlighted the urgency of leak reduction, underground water leaks pose severe public hazards by washing away subsoil and causing dangerous road sinkholes.
Fortunately, modern diagnostic tools—such as miniature pipe-crawling inspection robots paired with AI-driven network mapping—can now detect hidden leaks and identify aging materials (like lead pipes) before catastrophic bursts and collapses happen. Integrating proactive diagnostics with smarter spatial storage designs could help bridge the supply deficit much faster.
Careful, Hannah. The political-managerial class in the UK thinks that words are all-important--you must, must say the right words--and real world events are negligible. (Until, of course, one such event affects one of their own.) You came very close to criticising the government there.
The larger problem is the soils failure to absorb the winter rain. Until you fix the soil. Holding in resivoirs leaves much loss to evaporation. Hydrated soil fills springs and is recycled via trees back into rain. Water is in cycle with life, pipes break the cycle, ultimately making things worse.
It's perhaps worth recalling that it wasn't just 'the Victorians' in the abstract that built much of the pre-1992 capacity, but public enterprise in the shape of local government. Is there a role here for strengthened Mayoral authorities? - the private sector has clearly failed.
I think that there may be alternatives to more surface water reservoirs - which can help where appropriate. Managed aquifer recharge is being used more and more in many countries - to store wet season rainfall for use in drier periods. I am not sure of the feasibility in the UK - in terms of access to appropriate aquifers - but it has been studied in the UK. Various documents and journal papers are available. One paper for a project in Suffolk indicated that the cost of storage was 18% of an equivalent storage reservoir (Hiscock et al 2024). Research is ongoing at Cambridge University.
The ? Is, will it just flood off removing topsoil and not being absorbed. Or has the soil been restored to high absorbing state. Probably not. So that wetness will mostly returned quickly to the ocean leaving risk to droughts behind. Read up on the flood drought cycle .
On privatisation: I don't think it's the case that water companies don't want to build reservoirs. Rather, it is the regulatory system where water companies needs special approval for their investment plans (or at least to charge what it'd cost to make the investments). The water regulator has prioritised lower bills (new build reservoirs add to bills) and therefore most of the water measures have been around conservation rather new supply.
In the Eastern Scottish Highlands, we've had a lovely summer: no heatwaves, very comfortable and enough rain for the farmers. Some reservoirs haven't recovered from a few dry years yet. The west coast has had quite a bit of rainfall - a relatively wet July and very green.
https://www.wildlondon.org.uk/nature-reserves/woodberry-wetlands
A lovely place to visit - perhaps a model of how to run a reservoir that people view as a comunity asset rather than something to oppose?
This would be a great approach. And water bodies in cities will also keep them cooler.
Really great read. And whilst a hot topic, I didn’t see anything about data centres and their water usage; surely demand is going to rocket due to them too??
Is it possible to break the data down by region? The UK has seen its annual rainfall increase, but is this true for somewhere like Kent?
Hi Hannah, many thanks for an excellent post.
Much of southern and eastern England is indeed underlain by major Chalk *aquifers*, which is not quite the same as your chalk streams. The chalk acquifer for London is buried beneath impermeable London Clay & is recharged by rainfall on the downs & Chilterns... although this in turn sustains groundwater-fed chalk streams.
So regional water-supply system serving the South East draws heavily on groundwater resources that are hydraulically connected to sensitive rivers elsewhere. I see by chance that there is another Hannah Ritchie on LinkedIn “PhD | FGS | Hydrogeologist at Envireau”, who you might connect with on this!
Finally, is privatisation the cause, or a regulatory system that was focused on reducing consumer water bills at the expense of longer term investment? The lever was indirectly in the hand of government
Many thanks, Hannah, for another excellent piece with well-reasoned logic (and a few surprises!).
In addition to endorsing Akara’s pertinent comment about data centres, I would also highlight that reduction in consumption through efficient fittings and user behaviour offer real potential gains. And these are not just in water supply itself, but in associated processes such as purification, water heating, and drainage and waste treatment.
I’m unsure of the UK regulations for water-efficiency, but a few years ago in New Zealand I did an exercise on national shower usage (for a notional population of 5 million people). In summary, the widespread adoption of low-flow showers (say under 6 litres/minute) could potentially save the equivalent of a modest river flow of water (both freshwater and grey water) and a modest power station for water heating - all with commensurate financial savings.
Thank you, Hannah. This is a very useful reminder that water scarcity is not simply about how much rain falls, but whether we have the foresight to store, move, recycle and manage water for the future.
For me, the bigger leadership question is how we create water abundance for people, nature and prosperity before scarcity becomes crisis. 💧
Having a little personal knowledge of a reservoir that was completed in 90s/00s I was curious about the extent of the data on Wikipedia. The current list is from a report covering 90% of UK reserves, and my guess is there are at least a few more. One of the reasons reservoirs are no longer built is cost.. the area I know had gravel deposits which were sold to cover the costs (and more) up until that market crashed. Would be interesting to dig into this a bit more.. new reservoirs are very tricky for communities (it took 20 years for planning permission in the case I know of) so the picture isn't so simple. The bigger question is whether there will be enough catchment area and rainfall to fill new reservoirs.. let alone the existing ones. I've heard of data (but do not have it to hand) that suggests this may not be the case. Again, an interesting line of research...
How about solar powered desalination plants for summer backup only? Or are they just too expensive and small scale to be worthwhile?
Having now gone off and read up a little bit, it looks like it would need some improvements in the current tech in order to make this work. Apparently existing plants are not only pain to take offline and restart but they also have to run at maximum throughput. There is no way to throttle back the process.
Hopefully some bright people will come up with a better design eventually.
Thank you for this brilliant and well-reasoned analysis, Hannah. I particularly appreciated your clarity in showing that the core issue is seasonal precipitation imbalance rather than annual rainfall, as well as your pragmatic stance that we need both new storage and aggressive leak reduction.
Your point about Victorian achievements resonated with me. In Japan, historical records show that the monk Kukai led the massive restoration of the Manno Reservoir in 821, completing it in under three months through remarkable community mobilization and advanced civil engineering. While modern safety and regulatory contexts differ, it offers an inspiring historical reminder that overcoming planning inertia is possible.
To address local opposition and lengthy timelines, smart alternatives to massive new surface reservoirs might also help—such as riverbed dredging to expand channel retention, multi-functional retarding basins, and underground storage that upgrade existing infrastructure with minimal disruption.
Crucially, as you highlighted the urgency of leak reduction, underground water leaks pose severe public hazards by washing away subsoil and causing dangerous road sinkholes.
Fortunately, modern diagnostic tools—such as miniature pipe-crawling inspection robots paired with AI-driven network mapping—can now detect hidden leaks and identify aging materials (like lead pipes) before catastrophic bursts and collapses happen. Integrating proactive diagnostics with smarter spatial storage designs could help bridge the supply deficit much faster.
Careful, Hannah. The political-managerial class in the UK thinks that words are all-important--you must, must say the right words--and real world events are negligible. (Until, of course, one such event affects one of their own.) You came very close to criticising the government there.
The larger problem is the soils failure to absorb the winter rain. Until you fix the soil. Holding in resivoirs leaves much loss to evaporation. Hydrated soil fills springs and is recycled via trees back into rain. Water is in cycle with life, pipes break the cycle, ultimately making things worse.
It's perhaps worth recalling that it wasn't just 'the Victorians' in the abstract that built much of the pre-1992 capacity, but public enterprise in the shape of local government. Is there a role here for strengthened Mayoral authorities? - the private sector has clearly failed.
I think that there may be alternatives to more surface water reservoirs - which can help where appropriate. Managed aquifer recharge is being used more and more in many countries - to store wet season rainfall for use in drier periods. I am not sure of the feasibility in the UK - in terms of access to appropriate aquifers - but it has been studied in the UK. Various documents and journal papers are available. One paper for a project in Suffolk indicated that the cost of storage was 18% of an equivalent storage reservoir (Hiscock et al 2024). Research is ongoing at Cambridge University.
We have a new one here in the good old USA, It's name is Indiana. It used to be a State, but recently has turned into the USA's largest reservoir.
The ? Is, will it just flood off removing topsoil and not being absorbed. Or has the soil been restored to high absorbing state. Probably not. So that wetness will mostly returned quickly to the ocean leaving risk to droughts behind. Read up on the flood drought cycle .
On privatisation: I don't think it's the case that water companies don't want to build reservoirs. Rather, it is the regulatory system where water companies needs special approval for their investment plans (or at least to charge what it'd cost to make the investments). The water regulator has prioritised lower bills (new build reservoirs add to bills) and therefore most of the water measures have been around conservation rather new supply.
In the Eastern Scottish Highlands, we've had a lovely summer: no heatwaves, very comfortable and enough rain for the farmers. Some reservoirs haven't recovered from a few dry years yet. The west coast has had quite a bit of rainfall - a relatively wet July and very green.