In the north of the department; the Oise, traversing the northwest, with its tributaries the Serre and the Aisne, the latter of which joins it beyond the limits of the department; and the Marne and the Ourcq in the south.
Below Kuhsan it receives fresh tributaries from the west.
River transport has some local value on the upper Sao Francisco and its larger tributaries, and this will be greatly increased when the Central do Brazil railway reaches the head of navigation on that river.
Reaches Benevento, near which it receives several tributaries; then curves round the mountain mass to the N.
None of the tributaries of the La Plata system thus far mentioned is navigable except the lower Pilcomayo and Bermejo for a few miles.