LONDON - One-quarter of the global population lives on the brink of running out of water, according to a new World Resources Institute analysis.

Those vulnerable populations are spread between 25 countries, mostly in North Africa and South Asia, that routinely use all of their available water, putting them one drought away from a “day zero” event in which taps begin to run dry.

The analysis projects that because of population growth and economic development, water scarcity will grow most quickly in sub-Saharan Africa, which will require four times as much water in 2080 as it does today.

Living with this level of water stress jeopardizes people’s lives, jobs, food and energy security. Water is central to growing crops and raising livestock, producing electricity, maintaining human health, fostering equitable societies and meeting the world’s climate goals.

Without better water management, population growth, economic development and climate change are poised to worsen water stress.