Twenty more "Niles" needed to feed growing population-leaders
Former world leaders urge U.N. Security Council to make water top concern
Dozens killed in clashes between Sudan army and rebels
Military spokesman says 45 rebels and 21 civilians were killed in the violence, among them women and children
S. Sudan's first Khartoum ambassador urges trade not war
Ambassador says Sudan's Bashir has promised to help speed up the return of thousands of southerners still trapped in legal limbo on the northern side of the border