“Day Zero” refers to the critical moment when a city's or municipality's water supply completely fails or drops to such low levels that regular tap water is shut off, forcing strict water rationing. Smaller cities in Australia and South Africa have already experienced recurring “Day Zero.” Today, these cities manage to avoid complete system failure through aggressive public conservation campaigns, reduced consumption, rationing, water recycling, and desalination.
Since 2019, at least 25 countries around the world, including Belgium, Bahrain, Chile, Iran, and Lebanon, representing nearly one-quarter of the global population, have faced extremely high water stress each year. This means they use more than 80% of their available water supplies (Source: WRI). In addition, several of the world's largest cities, including Cape Town in South Africa, which came close to “Day Zero” in 2018, as well as Sydney and Melbourne in Australia, Chennai and Bengaluru in India, São Paulo in Brazil, Jakarta in Indonesia, and Mexico City, have faced severe water shortages and have come dangerously close to reaching “Day Zero.”
There are multiple factors that contribute to “Day Zero,” including rapid population growth, prolonged droughts, poor water management, groundwater pollution, excessive irrigation, and climate change.