Hannah with chief scout Bear Grylls and Jack Abrey
Hannah Kentish, from Abbey Wood, is travelling to the island on March 29, where she will in take part in Scout camp activities aimed at raising awareness of the importance of safe, private toilets and good hygiene.
The 23-year-old will then travel to local communities to encourage people to change their habits, which could save the lives of thousands of people.
Hannah, who attended Bexley Grammar School, said: “I’m really excited about the trip - but also quite nervous.
“I joined the scouts when I was 10 years old because one of my neighbours was joining and I was quite a shy child - and now I am getting the trip of a lifetime out of it!”
Nearly 12 million people in Madagascar do not have access to clean water and 21 million people do not have anywhere safe to go to the toilet, meaning 2,100 children die every year from diarrhoeal diseases.
Hannah said: “You just assume that clean water is something people do have access to generally. It just blew my mind that so many people are living in those conditions.”
Hannah will be able to teach the skills she learns in Madagascar to Scout groups in the UK that have pledged to support the WaterAid charity.
“When I was young, the thing I loved about the Scouts was it was different from school and a different environment where I got loads of opportunities to do new stuff. Scout leaders are like mentors rather than teachers.
“Now it is about being able to give something back and support young people on their own journey.”
WaterAid aims to help ensure everyone in the world has access to clean water by 2030 as part of the A Million Hands campaign, which 209,000 young people have signed up to support.