Today, billions of people are still living without safe water–their households, schools, workplaces, farms and factories are struggling to survive and thrive. In other parts of the world, water might traditionally have been abundant, but a changing climate and under-financed infrastructure pose new challenges.

March 22nd is World Water Day, dedicated by UN-Water to raising global awareness on the human right to access clean water and sanitation. The day represents a step on a long path–getting us closer to realizing the sixth Sustainable Development Goal (SDG1) of the UN 2030 Agenda. This year, World Water Day addresses the human right to water under the theme Water for all—leaving no one behind.

But first, let us take a step back to ask what “safe water” means. Under the UN’s definition, safe water is shorthand for a “safely managed drinking water service”–water that is accessible on the premises, available when needed, and free from contamination. The immediate thought might be to confine the issue of leaving no one behind to areas with less developed water supply infrastructure, extremely high population densities or naturally severe water stress. However, the application is much broader, and extends across the world. The key lies in understanding what leaving no one behind means from within one’s own sphere of influence. Even in California, which ranks as the world’s fifth largest economy, well over half a million people lack access to improved sources of water.2