Fountain Girl by Patricia S. Bowne

SPFBO8

Paio's brother has come back to the village! But he's come home to die, and to require a promise that will change her life. She has to reveal the magic talent she's hidden, go to the far-away city of Selanto for training, and find his lost child -- before the water they all depend on is lost forever. Paio doesn't realize that the people most determined to stop her are right in front of her.