Tokyo is currently the largest city in the World with a population of over 38 million people (greater Tokyo area - 13 million in the city itself). As a megacity, Tokyo experiences a range of sustainability pressures and water management is no exception. I was recently in Tokyo for a meeting to develop the International Water Association World Water Congress programme, which is being held in September 2018. Water use and water efficiency will be a key element of the programme linked to resilience issues. I visited the Tokyo Sewerage Museum "Rainbow" to learn more about water management in the city.
Water demand in Tokyo has fluctuated with economic growth and population increase. It is expected to peak between 2018 and 2027 at a maximum of 6 million m3 per day (Outline of the Tokyo Waterworks Bureau).
Average water consumption in England, UK, is around 140 litres per person per day. The EST At Home with Water report outlines water use for the UK based on a water and energy calculator. This results from this report showed showering to be the largest water user (25%) followed by toilet flushing and then other (cold tap) use.
London is the one of two cities in Europe in the top 50 worldwide by population. Current consumption in London is on average 146 l/p/d. Thames Water is forecasting a deficit in supply compared with demand of 864 million litres per day by 2100.
From the draft Water Resources Management Plan for Thames Water we can also compare where water is used in the home. The figures for unmeasured and measured (metered) households in London are below. For metered homes (the most comparable), the largest water use is personal washing followed by toilet flushing.
Where is water used in households in Tokyo?
Based on a survey by the Bureau of Waterworks in the Tokyo Metropolitan Government, average water use per person is about 230 litres per day. The highest use is flushing toilets (64l), followed by taking a bath or shower (55l) and cooking and washing dishes (53l).
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| Average water use in Tokyo is 230 litres per person per day |
The museum has an interactive household where you can actively use water and see how it drains away in the system. You can see how much water is used when you flush a toilet for example.
Water demand in Tokyo has fluctuated with economic growth and population increase. It is expected to peak between 2018 and 2027 at a maximum of 6 million m3 per day (Outline of the Tokyo Waterworks Bureau).
How does this compare internationally?
The International Water Association collects statistics on a range of issues, including household water use. The latest figures from 2014 are in the figure below, where Tokyo is within the top third of consumption.
Average water consumption in England, UK, is around 140 litres per person per day. The EST At Home with Water report outlines water use for the UK based on a water and energy calculator. This results from this report showed showering to be the largest water user (25%) followed by toilet flushing and then other (cold tap) use.
London is the one of two cities in Europe in the top 50 worldwide by population. Current consumption in London is on average 146 l/p/d. Thames Water is forecasting a deficit in supply compared with demand of 864 million litres per day by 2100.
From the draft Water Resources Management Plan for Thames Water we can also compare where water is used in the home. The figures for unmeasured and measured (metered) households in London are below. For metered homes (the most comparable), the largest water use is personal washing followed by toilet flushing.
How water efficient is Tokyo?
Comparing water efficiency based on per capita consumption alone is too simplistic as there are many different approaches to calculation and it doesn't account for wider factors that explain water use within cities.
The International Water Association Efficient Urban Water Management Specialist Group has been undertaking research on comparing water efficiency in cities over the past few years. I wrote a blog post about it here. When using a wider range of metrics as in the Sustainable Cities Water Index 2016, Tokyo is actually rated number 6, whilst London is rated 34. This can be attributed to greater metering and water recycling in Tokyo, even though the city has a higher PCC.
There is potential to reduce consumption linked to toilet flushing and showering/ bathing in Tokyo. This could come from improved efficiency of new devices, retrofit programmes and behaviour change. The Bureau of Waterworks states that they carry out a range of PR activities on concrete actions households can take to reduce consumption. They have also required manufacturers to develop and promote water efficient devices (Stable Supply of Potable Delicious Water).
Join the conversation on water efficiency through the IWA
The World Water Congress will take place on 16-21 September 2018. Come and learn more about water use in Tokyo, water efficiency, resilience and drought management. Super earlybird registration is open until 30 March!
We are also accepting abstracts for IWA Efficient 2018 until 30th April 2018. This is the major international conference on efficient urban water management and will be held in Manila.
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