London: Increased droughts and demand 

Emma writes*

To many, London means the Thames, Big Ben, and rain. But London shouldn’t be known for rain, as it receives less rainfall than Dallas, Rome, or Sydney. Looking to the future, Water UK suggests that London will face more severe, frequent droughts.

The city already experienced a major drought in the winter of 2011-12. Facing shortages, London’s water utilities asked for a drought permit to allow them to increase supply. If it wasn’t for the extremely wet spring and summer to follow, heavy restrictions on demand would have been necessary. As droughts are likely to occur more frequently and as precipitation will become more uncertain, London cannot expect to always be saved by rain.

Thames Water gets 30% of its water from aquifers and 70% from the River Thames and the River Lee. Rainfall influences river flows and groundwater levels. According to Professor Adrian Butler of Imperial College London, the issue is that London relies on winter rainfall to meet demand for the entire year. “If you have a succession of dry winters, you are facing a catastrophe in summer.”  Due to climate change summers are likely to become drier and winters will be wetter. The increased rainfall in the winter will likely be experienced as extreme downpour which is hard to capture and save for drought. Thames Water anticipates that summers will be 3C warmer and 18% drier on average by 2050. In the United Kingdom, climate change will decrease available water by 7-17 percent.

A lower and uncertain supply is not London’s only issue. The population of London is expected to increase by 100,000 each year and is likely to be above 13 million in 2050. The growing population in combination with household growth is predicted to increase the water demand in London and the Thames Valley by 46-90%, depending on the conservation scenario. Besides greater population and household sizes, hotter and drier summers also raise water demand. The 2018 heatwave lead to a 30 percent increase in household water demand. The figure below compares London’s increase in demand with its decrease in supply, showing how their difference — a gap indicating shortage — will increase over time.

London supply and demand (megaliters per day) Source [pdf]
Bottom-line: London is not the rainy city we imagine. Due to climate change, the city is likely to experience droughts more frequently and more severely, resulting in a decrease in water supply. In combination with an increase in demand due to population and household growth and climate change, London’s risk of water shortages is increasing.


* Please help my Water Scarcity students by commenting on unclear analysis, alternative perspectives, better data sources, or maybe just saying something nice 🙂

Author: David Zetland

I'm a political-economist from California who now lives in Amsterdam.

6 thoughts on “London: Increased droughts and demand ”

  1. Thank you for sharing a little more about London Emma! I have learned a lot from reading this!
    I must say that I also see a lot of parallels with my own case study (Atlanta) where droughts combined with population growth come together to amplify scarcity challenges. I would love to connect and maybe share our findings as we continue moving forward with research! Another point that stood out from your post is the “imagined” rainy city. Do you think that the perceptions of water abundance contribute to current consumption levels?

    1. Hi Ana Nico,

      Thank you for your comment.
      I definitely think that our perception of water abundance influences our consumption. When we perceive a place as rainy, there are often no visual cues to remind us of water scarcity. The possibility of water being scarce is unlikely to cross our minds when we see it as abundant. This also influences the way we consume it, as it reduces incentives to save water, and thus could lead to increased consumption. We need to stop perceiving water as abundant in order to lower consumption, and thus use water in a way that is appropriate to its scarcity.

  2. Hi Emma, such an interesting but also surprising post. Indeed, I always connected London with a lot of rain. I am wondering though what an emergency drought permit is and how London was able to increase supply after the drought in 2011/12? Also, there are quite some similarities between London and my case study city as Cape Town as well, relies on exclusively rainwater and has an increasing population. However, differences in income, equality, and financial means might lead to different approaches to fight scarcity. I think it is worth it to compare these approaches and see how external factors influence the solution-finding process.
    Lastly, I think many people (including myself) did not see water scarcity in Europe as a risk of climate change. At least as nothing to be concerned about so soon. Your post and also the graph really empathized the risk of water scarcity and its urgency to act.

    1. Hey Laura,

      Thank you for your comment!

      A drought permit allows water utilities to take out emergency supplies in case of a serious deficiency of water supply or an extreme shortage of rainfall. The drought permit authorizes the water utility to take water from additional (specified) sources and modifies obligations or restrictions water utilities face concerning the abstraction of water.
      The drought London faced in 2011/12 was ‘solved’ by the extremely wet spring and summer that followed. The large amount of rainfall was enough the bring the reservoirs back to their normal capacity.
      It is interesting that there are many similarities between the situation in Cape Town. I am curious to see if and how the approaches of the two cities differ.
      I was also surprised to see how pressing water scarcity is in London. It sadly is something we should be concerned about and needs to be acted upon rapidly to stop it from worsening.

  3. Hi Emma! Very nice post. It was very easy to read and follow your (chain of) ideas and you started strongly with that captivating fact and ended with the shocking illustration of the discrepancy between supply and demand that awaits London around the bend. One question that came to me as I read through, beyond my surprise at the introductory fact, is: how is their estimate increase in temp predicted at an average of 3°C? the grand max of the world is 2°C by that point no? Perhaps I have the number wrong but its quite surprising to hear this because London strikes as such a cold and wet place. Additionally, when you speak of drought, how exactly is it defined for London? I’m guessing it must be relative to something correct (because it can’t be the same kind of drought as California right….)?

    1. Hi Clara,
      Thank you for your comment!
      An increase of 2 degrees celsius is indeed the tipping point for the world. The 3 degrees increase mentioned in this blog post is the regional increase in London’s average summer temperature. Regional and seasonal variations are not included in this number. The winters might be colder and other areas around the world might not experience such an increase in temperature. The global average temperature increase can thus lay belwo the 2 degrees celsius.
      The U.K defines a drougth as a period of at least 15 consecutive days with rainfail below 0.2mm. This illustrates that there still can a very small amount of rain during a drought. I can imagine that this differs from California’s definition.

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