Last month, you might have seen two young girls on the side of London's buses, each hauling a jerry can of water that is more than half their weight.
Some 748 million people around the world do not have access to safe water. That is one person in 10. It is nearly always up to girls and women to hike treacherous, winding paths to fetch water for their families, and carry that heavy burden home again.
Ze and Solo are best friends from the African island of Madagascar. This is the last in a series following them as they share their story of what it means to be a girl.
Part 4: The road ahead
Solo and Ze are best friends. Like 12- and 13-year-old girls around the world, they talk about everything. But their conversations don't focus on music or boys. Even at this young age, their lives are consumed by the need for water.
Ze told me: "Solo and I talk about anything, if we start talking about having the water point up here, we don't stop talking until we get back.
"When I have a family it will be totally different. I hope we will be able even to wash and do our laundry here at home. And when we will have the water point up here, that old water point can be used for the rice field, it would be good for tomato and onion growing, so there would be more food. ... I will be able to plant flowers and trees all around, because it's not difficult anymore to have access to water.
"In the future, I will take care of my parents, like they have taken care of me. ...With clean water I will be stronger, I will be healthier. When water comes to my community, it is going to be wonderful here."
Pictures of a better future
The girls had never used a camera before. So we gave Solo and Ze small disposable cameras and taught them how to use them.
These are some of the images they captured of their everyday lives - stark and beautiful. But they bear little resemblance to the childhood I experienced and took for granted.
A portrait of Solo - WaterAid/Zemiso Iarinirina
WaterAid/Zemiso Iarinirina
WaterAid/Soloniaina Rasoambola, Zemiso Iarinirina
WaterAid/Soloniaina Rasoambola
In Madagascar, nearly 11 million people are without access to safe water, and more than 18 million people do not have access to even a basic toilet. More than 4,000 children here die every year of diarrhoeal diseases linked to the lack of safe water, basic toilets and handwashing.
WaterAid works with small remote communities like Solo and Ze's to provide safe water sources. In the community of Alakamisy, the installation of eight water taps around the village has transformed lives - making people healthier, their gardens more productive, and their animals stronger. Children are now able to attend lessons instead of hauling water, and adults have time to sell garden produce in the market.
Help WaterAid help Solo, Ze and thousands of girls like them this summer.
The Department for International Development has agreed to match all donations received this summer for WaterAid's campaign, To Be A Girl, to bring safe water and basic sanitation to some 130,000 girls in developing countries to bring better health, safety, education and a more promising future.
WaterAid/Abbie Trayler-Smith