Gitanjali Rao was selected from 10 finalists who had spent three months collaborating with scientists to develop their ideas.
Her device uses carbon nanotubes to detect the presence of lead.
Thousands of US water systems are reportedly contaminated by lead.
Gitanjali's invention was inspired by the scandal in Flint, Michigan, where officials are facing charges including manslaughter over water contamination in 2014-15, she told Business Insider.
Media captionFlint resident Melissa Mays: 'Our hair fell out'
