Earth is about 71 percent water. An overwhelming 97 percent of that water is found in the oceans, leaving us with only 3 percent in the form of freshwater—and much of that is frozen in the form of glaciers. That leaves just 0.3 percent of that freshwater on the surface in lakes, swamps, springs, and our main sources of drinking water, rivers and streams.
Despite our planet’s famously blue appearance from space, thirsty aliens would be disappointed. Drinkable water is actually pretty scarce.
As if that doesn’t already sound unsettling, what little water we have is also threatened by climate change, urbanization, pollution, and a global population that continues to expand. Over 2 billion people live in regions where their only source of drinking water is contaminated. Pathogenic microbes in the water can cause cholera, diarrhea, dysentery, polio, and typhoid, which could be fatal in areas without access to vaccines or medical treatment.
