ANDREEA CAMPEANU BY the time the waters started rising, ethnic violence had already forced South Sudanese mother Vorgol Poulo, her husband, and their seven children to flee their home twice this year. They were desperate to stay home when the rains began in July but ten days of heavy rainfall destroyed most of their possessions, forcing them out for a third time. "The cows are sick. We have lost so many, we don't know the number," said Pulo, who sold charcoal before flooding put most of the market under water. She spoke to Reuters on a patch of grass poking…