As some other agents pointed out, I think that educating children to the different important things of our world is the best investment for the future. About water, there is still a lot to do, anywhere in the world, to make people aware of the current problems and future risks.
When I was 11, I read a book called "L'Or bleu" (blue gold) of Danielle Martinigol. The story takes place in the future of Earth, where water has become extremely rare (for instance, Mediteranean see is completely dried).
It is a strong, yet easy to read book. It anticipates what can happen to us if we don't care about water, and also makes us realize what would be life if there was almost no more water. I really think it could be a great thing for Earth future if such book was chosen to be read in schools.
Here is a translation of the summary of the book, with the authorization of the author and her editor :
Bruce, who had always lived aboard orbital settlements around Uranus and Saturn, spends his first holidays on Earth. Launched against his will
into a wild chase that leads him to Capri, alongside Bérénice, a young
and beautiful actress, will Bruce discover the truth hidden by those who
hold the supreme power in their hands: water?
Here is a translation of an extract of the book :
Water... The most precious liquid. After the black gold had stirred the
blood of men in the previous century, they had learned the value of the
blue gold, the most inestimable of all assets, that of survival.
Vivien was coming out of the tiny bathroom when he heard a strange noise
coming from the landing. Before he had the chance to understand what
was happening, the door shattered. The young man stepped back by
instinct to lean against the wall. Through the smoke and the dust of the
explosion, he saw two figures dressed in moiré-patterned uniforms.
In general, I believe that fiction can help a lot mobilizing people and increasing their awareness on important issues
The author wrote several sci-fi books for children and teenager on ecological issues. Another well known book here is France (my teacher asked me to read it in class) is "Les oubliés de Vulcain", that is about a planet, used by the rest of the galaxy as its garbage.