Addressing imbalance in water supply and demand: innovation and behaviour change

California, USA: Michael Drennan, Vice President, WSP California Water Business

California experienced a serious drought between 2011 and 2017 – it’s been recognised that this is a result of climate change – we’ve seen markedly less snow over that period, which is important to our water supply. As a result, the region has needed to focus on water scarcity, and diversifying our supply.

The largest municipal water agencies in the state – responsible for Los Angeles and Southern California – have set visionary goals which aim to: recycle up to 100% of wastewater, capture more stormwater, recharge more groundwater and conserve more water. One initiative has been offering ratepayers up to $3 per square foot to replace their grassy lawns with drought tolerant plants. They have also implemented massive public education programs and regulations to modify behaviour regarding water usage (water conservation, low-flow toilets, low-flow shower heads, reducing outdoor landscape watering). Since 1990, the state has successfully reduced water use per capita by 20-30%.

In Southern California, WSP is working with Arcadis and Balfour Beatty to build a new wastewater recycling plant that will treat 10 million gallons per day (438 litres per second) and recharge a local groundwater drinking aquifer. In San Diego meanwhile, there is a multi-billion-dollar, multi-year indirect potable reuse project in progress that will use advanced treatment technology to purify 30 million gallons per day (135 million litres per day) of recycled water.

LA Sanitation runs a recycled water filling station outside one of its water reclamation plants. The disinfected water here can be collected by residents for free and used in place of potable water for landscaping.

Sweden: Anna Dahlman-Petri, Senior Consultant in Water at WSP

In Sweden we historically have had a lot of fresh water and few historical issues with supply. However, for the last several years in a row, we have experienced drought. With climate change this is likely to become an increasing challenge.

Like the UK, we have also experienced flooding issues, like a cloudburst event in central Stockholm, which affected city-centre properties and as a result, was very high profile.

In locations like Stockholm, where the population is rising, addressing these challenges within existing capacity is increasingly an issue. 

We’ve started to look at new technologies and solutions that can increase supply – like desalination, combined with behaviour change campaigns. We’re using sustainable urban drainage schemes to help mitigate extreme rainfall. 

At a consumer level, we need to address similar challenges to the UK: cost isn’t a strong motivator of change. As we move to a climate of greater extremes, the public need to be more aware of potential supply issues and the work that goes into ensuring continuity of supply. 

The challenge is: how much can you intervene in how much water individuals use? Can we expect them to only use a certain amount of water when brushing teeth or use the washing machine at certain times? We could nudge consumers or businesses towards using water outside of peak hours. Could industry for example, draw more on water supplies at night?

It’s interesting to see from the UK results that people would be willing to moderate their behaviour for environmental reasons. We need to learn from that.

I’m quite surprised by the UK research finding that people think their tap water is of insufficient quality. The UK has some of the highest quality tap water in the world, so it strikes me that this is something that should be addressed by utilities. In doing so, they could draw on the environmental aspects of it: according to data from the Swedish Institute for Food and Biotechnology, the transport of bottled water gives rise to 1,000 times the carbon emissions of the same amount of tap water. 

In Sweden, we have the ‘Kranmärkt’ label – an initiative led by the Swedish Water & Wastewater Association. This label is applied to businesses and organisations who choose tap water over bottled water. 

Read WSP in Sweden's research

South Africa: Karen King, Senior Associate (Hydrology)

South Africa, and particularly Cape Town, experienced severe and prolonged droughts in 2019. It resulted in lengthy water cuts to private homes throughout the country. 

As a result of our supply issues, we have a tiered pricing schedule: a basic, initial volume of water used every month – an amount that is essential to survival, is very inexpensive, the next set volume is more expensive, and so on until what is termed ‘luxury water’ is very expensive.  A lesson learnt is that these tiers should be steep – piped potable water in SA is still used wastefully as it is under-priced.  

I would expect water pricing to be more effective in changing the behaviour of industry than citizens. The financial benefits of reuse, for example, can be used to the advantage of both industry and the natural environment.

There may be a way to communicate the long-term risks of failing to reduce consumption – needing to change the time of day we cook, clean and bathe, for example – if consumers don’t make short-term smaller-scale changes in behaviour.