Charles Ellicott Commentary Genesis 12:9

"And Abram journeyed, going on still toward the South." — Genesis 12:9 (ASV)

Toward the south.—The Negeb, or dry land, is so called because its soil is a soft white chalk, which allows the rains to sink through it; even in the valleys, the water runs below the surface of the ground. Though treeless, it is still rich in flocks and herds, but the water has to be collected in tanks and cisterns (Conder, Tent Work, ii. 87).