Will London run out of water?

Over the past few years, Thames Water has missed its leakage reduction targets. In 2017, the failure to meet these leakage reduction commitments cost the water company an £8.55m fine from the water regulator, only a fraction of the £100m the water company paid investors in dividends in the same year. Recognizing the scale of investment and effort required, the company now says it is directing all its resources towards upgrades and maintenance rather than dividends.

But there are limits to what can be achieved just by fixing leaky pipes or getting people to water their lawns less often. Though such measures are useful, they will not safeguard London’s water supplies against the more extreme combinations of growth and climate change.

Water recycling
Instead, the city’s water managers have been thinking about innovative ways to augment supplies. Potential solutions include building new reservoirs or transferring water from other parts of the country. More radically, London could start recycling its wastewater back into the river Thames. This would involve advanced treatment of wastewater from a sewage treatment works that is then returned to the Thames river downstream of an abstraction point. This would allow for more abstraction upstream, without compromising the environment’s water needs.

How should London choose between these different alternatives? The city needs something that’s not too expensive, that keeps residents happy with the price, taste and appearance of the water, while also reducing the risk of the taps running dry.

My colleagues and I looked at the various options – new reservoirs, water transfers, desalination and recycling – and the model we developed shows that the recycling of treated wastewater back into the river makes most sense from an economic and risk reduction standpoint.

Water recycling works in Singapore, where water is reused time and again, thus closing the loop between supply and demand – an example of the circular economy.

Yet all this requires a change of thinking. Traditionally, investments in new pipes or reservoirs are based on estimates of future water availability and needs. These estimates are based on past observations, which means that water engineers look at how much rain there was in the past and then assume that there will be as much in the future. Typically, this results in infrastructure that delivers a secure supply of water at the lowest cost possible – under “normal” conditions.

However, the future will be significantly different from anything imagined when water supply systems were first built. We will have to leave more water in the rivers for aquatic ecosystems to thrive. We will have to deal with more erratic rainfall.

To prevent London from becoming the next Cape Town, individual residents will have to use water as wisely as possible. And their water managers will have to focus on what will work even in an era of significant climate change.

Edoardo Borgomeo is Honorary Research Associate, University of Oxford. This article is published courtesy of The Conversation