To avoid reaching Day Zero, the campaign communicated clear, easy to understand actions that residents could take to conserve water. Examples of these behaviors included: flushing toilets using rainwater or grey water after defecating, taking sponge baths, using hand sanitizer in place of washing hands, and washing clothes less often. Posters designed to communicate these behaviors also outlined how much water might be used for various activities to remain under the 50 l limit. To keep water conservation at the forefront of everyday conversations and enforce positive social norms, a city-wide map was published and updated throughout the campaign that marked houses doing a good job saving water with a green dot.
Feedback was also regularly provided to residents whenever their water usage was going down, recognizing their efforts and motivating them to keep going. To encourage shorter showers, Cape Town partnered with some of South Africa’s most popular artists and had them cut down their top tracks to just two minutes (the ideal shower length). These shortened tracks were made available to residents to use while they showered and served as a light-hearted reminder to keep showers short. Throughout the challenge, businesses also became key influencers in changing water use behaviors as they increased conservation efforts among staff and customers in order to avoid high water prices.
Some businesses ran “dirty shirt” challenges to see how long employees could go without washing their uniforms while others placed signs in the bathrooms reminding people not to flush after urinating. In addition to the regular Day Zero campaign a school program was also implemented through a partnership between the University of Cape Town and Stellenbosch University. Branded the #SmartWaterMeterChallenge, this program encouraged students to harvest rainwater and bring water to school. 345 schools received smart water meters and basic infrastructure upgrades and were assigned a plumber that had a list of quick fixes and a budget of R 5,000. Schools were split into three groups for testing the impact of behavioral interventions – one group received weekly feedback reports with graphs illustrating water use, another group participated in an inter-school competition, and a third group served as the control.
Basic infrastructure repairs at the schools made by plumbers reduced water leaks by 28% within five days while the behavioral interventions led to reductions in water use of between 15% and 26%. City-wide, Cape Town measured the success of the Day Zero campaign using two main metrics – aggregate water served and reservoir levels/volumes. Additionally, research teams at the University of Cape Town and Stellenbosch University used smart meters to compare water use in a sample of homes in Cape Town to that of 103 homes in two other regions in South Africa, Mpumalanga and Gauteng. While these towns were not affected by the drought, they experienced similar drivers of change as Cape Town. While the most dramatic changes in behavior began in January 2018 with the launch of the Day Zero campaign, the City’s daily average water use fell from 1,200 million l (317 million gallons) in February 2015, to 500 million l (132 million gallons) in February 2018. From December 2017 to March 2018, the percentage of single-family homes using less than 10,500 l (2,773.8 gallons) of water per month increased from 64% to 81%, with those using less than 6,000 l (1,585 gallons) increasing from 31% to 49%. Consumers reduced average household water usage from 540 to 280 l/household/day over the 36 months between January 2015 and January 2018.