Please help I am searching for a book?

I read this story when i was young it was translated so i do not know the original name,

the story was about a city where water is very expensive and the poor can barely afford it, a lost cloud enter the city and befriend a poor little girl and together they find out that the emperor is keeping all the water so the girl and the cloud work together to free the water and make it again available for every one.

if you can help i need the name of the story and the author.

thank you for your help in advance.