Wastewater management in cities

The map that helped save Cape Town

Around 2016 to 2018 an extraordinary drought swept through Cape Town. The effect on the famous city was so severe, officials asked residents to stick to dramatic water restrictions. Capetonians had to limit their household water use to 50 litres of water per person per day.

Across the world, people sat up and took notice; especially when the mayor announced Day Zero was close. This was when water supply to households would be turned of, and people would have to queue for water at public points.

Staring at his computer screen in his office at the municipality’s Water Demand and Strategy branch, Ken Sinclair-Smith could see part of the solution. Ken specialises in information management and analysis, geographic information systems and water modelling.

“People were telling us that they could not possibly use any less water,” he says, “but analysis of water consumption for individual households showed large differences, even within the same streets.” While people in one household would be limiting themselves to meet the restrictions, their neighbours might not. Some people were simply not doing enough.

Ken Sinclair-Smith, section head for the municipality of Cape Town’s Water Demand and Strategy branch

Getting every household to stick to the restrictions was critical. Up to 70% of water consumed in the city of Cape Town, was done so in households (informal settlements use about 4% of water). To save more water, the key was to have people use less in their homes. Not only were they the largest group of water users, but their savings would spill over into much smaller impacts on the economy, than if bulk industrial users had to cut their water use.

Seeing part of the solution clearly displayed in the figures and data that he worked with, Ken had a plan. It was a map.

A map like no other

Famous the world over for its relaxed and friendly locals and spectacular scenery, Cape Town was a tense place during that drought. In late 2017 it was very hostile, says Ken. In the press, a lot of letters from people in richer areas blaming people in townships for wasting water were published, for example. Other articles put the blame on tourists. “It was very much a case of blaming other people; of someone else being the cause of the problem.”

Launched in January 2018, the map addressed this by publicly acknowledging households that saved water.

The green dot map is born

Cape Town’s water map or, the so-called green dot map, showed the water use of individual properties with different coloured dots. The map was published on the City of Cape Town website where anyone could access it.

Light green dots represented households that used less than 10 500 litres per month (or 87 litres per person per day for a four-person household). Dark green dots were awarded to households using less than 6 000 litres of water per month (the equivalent of just 50 litres per person). Grey dots were also used to show properties where individual household meter readings were unavailable. These could include sectional title properties or group housing, and properties without accurate water use information.

A ‘nudge’ in the right direction

The final water map was designed as part of behavioural-nudging research conducted by the University of Cape Town Environmental Policy Research Unit. The city had also been working with the UCT researchers to test which interventions are best to ‘nudge’ people to change their behaviour for better outcomes; in this case, reducing their water use.

The map applied social norms as ‘nudge’ to save water, by providing feedback on how residents perform in comparison to their neighbours. The map also demonstrated that sticking to the severe water restrictions was not just feasible, but already being done by friends and neighbours.

Initially, the map made provision for red dots to indicate households that did not comply. However, the final decision was to rather highlight positive behaviour. In an already volatile environment, the city did not want to contribute to any stigmatization of households.

There were also concerns about infringement on people’s privacy. But, an assessment of the risk concluded that in the context of the seriousness of the crisis, there were legal grounds to justify the publication of the information. The severity of the potential catastrophe would constitute legal defenses in any potential defamation proceedings.

A rocky start

Ken says they received negative feedback at first, especially since the map went live before the accompanying media pack was released. Due to the initial backlash in the media, the map nearly got pulled completely.

On the flipside, Ken says this really helped put the map, well, on the map. “It got a lot of attention.” And, when the official media statement was released, it got even more coverage. In fact, the city’s website almost crashed due to the sudden increase in traffic.

With the launch of the accompanying media campaign, “lets paint this city green”, and extensive information on the website to put the map in context, it quickly became a valuable weapon in the city’s arsenal to help drive down water use. Mostly, media coverage was balanced, and the map received public support via various social media platforms.

In the months following the launch of the water map, water savings increased dramatically.

World-record water savings

By March 2018, half of the city’s households were using only 6 000 litres or less, reaching the 50 litres target. A further 80% were using 10 500 litres or less. By May, 400 000 households were marked with the prestigious green dot. In total, Cape Town’s overall water use dropped by 55% from pre-drought levels – the greatest water saving ever achieved by a metropolitan sized city.

Still, the exact contribution of the map would be hard to define. At the time, the drive to drop water use in Cape Town was a sustained drive from multiple directions.

For one, the mayor announced that Day Zero was likely to arrive unless more people saved water. The price of water increased, and stricter water restrictions were applied. The city ran continuous communication campaigns to motivate people to use less water, supported by easy and practical tips on how to do so. Substantial savings were also achieved by further lowering the pressure in the water network. (Less water come out of the pipes, and there are fewer bursts.)

Yet, as part of the overall effort to decrease water use in Cape Town, the map made an important contribution.

There are many lessons to be learnt from the Cape Town Water Map for other cities experiencing a similar crisis, especially for those with high- and middle-income areas where water consumption needs to be lowered.

Lessons from the map

For one, public acknowledgement and reward are powerful forces to drive behaviour change.

To create such a platform, especially one that can be controversial, collaboration across departments is essential. Support from a good communications team is integral, says Ken. In the case of the Cape Town Water Map, partners included the city’s Water Demand Management branch, legal support services, information systems and technology, the Corporate GIS Department, finance and commercial departments.

Prompt replies to public enquiries were also important. The city created a dedicated complaints line especially to handle complaints and enquiries. Quick answers to resolve any questions prevented unnecessary escalation of complaints.

Though quick to implement, and a low-cost intervention, he points out that the information systems necessary to have made the water map work effectively should not be underestimated.

Technology as part of the future for saving water

Though the map has now been taken offline, the City of Cape Town is still relying on technology to share information with the public. One of the most important tools is the water dashboard, that provides real time information to help reduce water consumption (another ‘nudge’).

This dashboard type report shows dam levels (measured by the National Department of Water and Sanitation) and how much water is available. It also shows whether water restrictions are necessary. Then, it provides projected dam levels up to the end of the hydrological year (1 October). This gives people more confidence that the situation is being managed, says Ken.

They key, he says, is that during times of crisis you cannot only rely on enforcement for people’s support. “When a water crisis hits, you need to bring the public along with you.”

Savvy use of technology and in Cape Town’s case, the water map, were essential to help people understand that, over and above interventions by the municipality, each and every person needed help save the city that they called home.



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