(CNN) Our connection to water is elemental; it courses through our bodies, winds through our cities and countryside, covers 70 percent of the Earth's surface.
Yet the lifeblood of our planet is facing a crisis. Around one in three people worldwide, or 2.2 billion, lack access to safe drinking water near their home. Every day, 800 children under five die because of contaminated water and poor sanitation.
By 2025, half of the world's population will be living in water-stressed areas -- when resources in a region or country are insufficient for its needs.
Deepika Kurup, 21, had a comfortable upbringing in Nashua, New Hampshire. Her father was a civil engineering professor who encouraged her interest in science and allowed her to set up a laboratory in the garage.
Her India-born parents took her to visit the country every year, and it didn't take long for the young girl to realize how different it was from the United States.
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One day, at 14 years old, she noticed children around her age using plastic bottles to collect water so obviously dirty she wouldn't go near it. "That really struck me," she says. "That's the only water that they have to drink and that same water they use to wash their clothes and cook their food."
Kurup understood that not having access to clean water meant not having clean clothes or food. She learned that for girls, it also restricts access to education, because they cannot attend school when they have their period.
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"So water also affects women's health and ... how women can contribute to the economy, because instead of spending time with their family and instead of spending time working and raising money, women have to walk hours on end every day to go collect water," she says. "That definitely is not something that I used to see in the United States and so I wanted to do something to change that.
"Just realizing how much of an impact water has on the everyday lives of millions of people around the world is ... what drew me to this problem."
In response, Kurup created an affordable and effective water purification system -- a cement-like composite material that is activated by sunlight to dramatically reduce the number of bacteria in water.
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The material can be molded into different shapes: a rod placed in a drink bottle; a disc or pot to filter the water or a coating for the inside of a water tank. "I definitely see it as something that could be scaled up or scaled down to whatever works best for the community," says Kurup.
She got to show her invention to Barack Obama in 2012 and won a slew of awards, including "America's Top Young Scientist" in 2012; the US Stockholm Junior Water Prize in 2014 and the National Geographic Explorer Award at the 2015 Google Science Fair.
But as the accolades piled up, Kurup recognized that "this solution alone isn't going to be what solves the water crisis" -- the problem is just too complex.
"There are a lot of different ways to approach it," she says. "Some ways might be better than others in different situations." Her sunlight-activated material will be more effective in sunny parts of the world, for example.
Kurup believes the solutions lie in a combination of policy, scientific research and activism. "I think it's definitely going to be the integration of different solutions when it comes to tackling such big challenges, like climate change, or other environmental issues or other medical issues," she says.
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She has just completed a degree in neuroscience at Harvard and is about to start a medical degree at Stanford.
She has been studying global health policy and hopes to learn more about it during her degree, and spend a year working in medicine in India.
Kurup patented her technology last year and is searching for a company that is already working in the developing world to implement it.
"Specific communities have specific needs and so I would like to see my technology deployed in a space where that community would really, really benefit from it," she says. "There are so many different avenues in which you can impact the world around you ... working with patients on an individual level, but also working on policies that can shape lives on a much bigger scale."
Kurup still returns to India every year, and sees young people who face a daily struggle for clean water.
It reminds her of how the rivers that sustain us ebb and flow -- they cannot be taken for granted.