Cape Town’s Water Map was launched during an intense drought, estimated to be a 1 in 590-year event, when the city was at risk of running out of water. Water consumption, while much reduced, remained persistently higher than the saving levels required in spite of water restrictions and extensive awareness campaigns. It was critical to rapidly reduce water consumption especially in single-family residential homes, which accounted for more than 54% of all water consumption in Cape Town. Analysis of water consumption for individual households showed large differences in water use within neighbourhoods. This suggested that individual households were responding very differently to the water crisis.

The main goal of the water map was to publicly acknowledge households that saved water, thereby normalizing and incentivising water conservation behaviour. A further aim was to demonstrate to skeptical citizens that compliance with the severe water restrictions imposed by the city was not only feasible but had already been achieved by their friends and neighbours.

The Water Map was an integral part of the city’s drought response strategy that emphasised public awareness, transparency and the empowerment of citizen by providing ample information on water usage.

An online spatial viewer using GIS data displayed colour-coded green dot symbols to indicate single-residential properties achieving water saving targets:

• Dark green dot: household using 6 000 or less litres per month

• Light green dot: household using between 6 000 and 10 500 litres per month

Properties where individual meter readings were unavailable (e.g. sectional title property or group housing) and properties without accurate water use information (e.g. properties with estimated water consumption) were indicated by grey dot symbols.

The map was supported by a media campaign (“Let’s Paint This City Green”) that praised water-saving households and encouraged all households to achieve similar savings. A frequently asked questions document and supporting information were prepared in order to contextualize the map, provide guidelines for its use and interpretation, and provide information on how the thresholds for the green dots were calculated. The Water Map was further promoted by press releases and social media posts reporting on the total number of green dots achieved each month, which were timed to coincide with the monthly map update.

The Water Map viewer was developed and updated by City of Cape Town officials using existing software. It was thus developed and maintained at no additional cost to the City.

The design of the Water Map was informed by previous behaviour research undertaken at the City by rearchers from the University of Cape Town Environmental Policy Research Unit in terms of a research partnership agreement.

Key stakeholders in this project were:

• City of Cape Town: Water Demand Management Branch – project lead
• City of Cape Town: Communications Department – communication strategy, marketing, website and social media
• City of Cape Town: Legal Support Services – legal evaluation and legal input
• City of Cape Town: Information Systems and Technology – web viewer development and maintenance
• City of Cape Town: Corporate GIS Department – data structure and web viewer design
• City of Cape Town: Finance & Commercial – monthly water consumption data
• University of Cape Town: Environmental Policy Research Unit, School of Economics – application of behavioural science theory and input on web viewer design and evaluation

The map was first published in January 2018, and after the first media reports the website experienced some of the highest Internet traffic ever by a City of Cape Town webpage. Within the first week, a number of local newspaper articles on the map had been published, and it received substantial attention on social media.

Residential water use dropped considerably and Cape Town’s overall water use declined by 55% from pre-drought levels – the greatest water saving ever achieved by a metropolitan sized city. In May 2018 the International Water Association awarded a Certificate of Achievement to the City for reducing water demand by 55% in two years without resorting to intermittent supply. These water saving achievements greatly contributed to the City not running out of water and “avoiding Day Zero“.

Water saving behavior increased dramatically in the months following the launch of the Water Map as shown by the graph below. By March 2018, half of the City’s households were using only 6000 litres or less per month (equivalent to approximately 50 litres per person per day or less) and 80% were using 10 500 litres or less.

In May 2018, the City awarded “green dot” status to 400 000 water saving households – the highest number achieved to date.

While the Water Map played an important role in encouraging water saving behaviour, Cape Town’s remarkable water saving achievements should be attributed to responsiveness of Cape Town’s citizens and businesses, the City’s overall drought communication strategy, the January 2018 announcement by the mayor of Cape Town that Day Zero was likely to occur unless more people saved water, the introduction of higher water tariffs in February 2018 and more stringent water restrictions as well as the intensification of efforts to lower water network pressures from December 2017.

The publication of the Water Map raised concern that the map could stigmatize households or suburbs not complying with the severe water restrictions in place at the time. A further concern was that the map could actually discourage water saving behavior by drawing attention to the large number of households that were non-compliant with the water restrictions and still using too much water.

These concerns were mitigated by focusing on positive behavior and by only identifying households on the map that were saving water. City communications emphasized the importance of social cohesion in the drought crisis and stressed that the map did not necessarily imply compliance or noncompliance with water restrictions. Possible reasons for higher water consumption, such as a high number of household occupants or an undetected water leak, were also outlined. A complaints line was established to investigate and correct potential errors.

Concerns that the water map would exacerbate tensions between different socioeconomic groups did not ultimately materialize, and it is thought that the map may even have helped reduce stigmatization and scapegoating by showing that every neighborhood, rich or poor, included households that were saving water. No defamation suits have been filed, and the city received few complaints regarding the infringement of privacy. All reported errors were investigated, and very few actual errors were found.

The Cape Town Water Map is of relevance to cities in water stressed regions. It was highly effective in raising water saving awareness and an important mechanism for encouraging behavioural change during the recent Cape Town drought crisis. It is particularly effective as a drought intervention as it is quick to implement, low-cost and effective in high and middle income areas which generally consume more water relative to low income areas.

The Water Map and earlier Cape Town based research indicates that public acknowledgement and “reward” can be a powerful force for behavioural change.

• City of Cape Town, Water Map information page, www.capetown.gov.za/watermap
• City of Cape Town, Water Map viewer, https://citymaps.capetown.gov.za/waterviewer/
• City of Cape Town’s Water Map, Journal of American Water Works Association, September 2018, https://awwa.onlinelibrary.wiley.com/doi/pdf/10.1002/awwa.1154
• City of Cape Town, 15 January 2018, Press Release: Let’s paint this city green. http://www.capetown.gov.za/Media-and-news/Let's%20paint%20this%20city%20green
• City of Cape Town, 27 June 2018, Press Release: Cape Town achieves record number of green dot households in May, http://www.capetown.gov.za/Media-and-news/Cape%20Town%20achieves%20record%20number%20of%20green%20dot%20households%20in%20May