The Army Corps of Engineers is trying to manage the Mississippi River, the world's third biggest watershed after the Congo and Amazon. But blasting two miles of levees to ease a threat to Cairo, Illinois means flooding farms in Missouri, and there's rising concern down the river all the way to Louisiana and Mississippi. Flood levels have dropped in Illinois, but Missouri farmers are going to court, and there've been precautionary evacuations in Tennessee. Last week, Governor Haley Barbour started warning about possible flooding in Mississippi. Michael Grunwald writes about efforts to manage water resources for Time magazine.