Whether it's China’s disappearing rivers or the empty reservoirs of Brazil, the world's safe and drinkable water is drying up. Raising awareness of the impending global crisis is Mina Guli, businesswoman and founder of water conservation charity Thirst, who is running the equivalent of 40 marathons, across seven deserts in seven continents – in just seven weeks.

You can watch some of her desert runs in these three videos.

“Most people don’t know that we’re going to run out of usable water,” says Guli, a Young Global Leader at the World Economic Forum, where a survey of 750 experts rated water scarcity the number one risk to global society over the next decade. “By 2030, there will be a 40% difference between the demand for water and the supply of water available. We’ve got 15 years to solve the water problem," she says.

In the past two decades, 55% of China’s rivers have disappeared due to industrial use. More than 70% of the western United States has been hit by drought, resulting in a loss to the Californian economy of around $2.7 billion. Increasing water stress is poised to trigger a global food crisis. “We think that it’s not going to be us any time soon," says Guli, "but the reality is, it is going to be us sometime soon.”