Completely Desert Basins

So dry that any overland flow is nonexistent and all water is absorbed by sand.

Dry Washes

Arid regions can have substantial rivers end in a non-channelized wash, all flow apparently absorbed by the sand. (sheet flow)

Non draining plateaus

flat areas (sometimes inland, sometimes coastal) where there is no evidence of water draining in any direction.

-18.16 17.16

Lakes with multiple drains

Deltas

Large rivers can have mutiple pours spanning a delta

The ambiguous ocean mask

Determining where the river ends and the ocean begins is not always clear.

Coastal Lakes

The upstream flow can end its journey at lake or lagoon that may or may not interact with the ocean. To complicate matters these coastal lakes can often spread parralel to the coast connecting by spurious little channels, subsuming multiple basins and potentially having multiple pours.

Examples

Libya (31.63 15.51)

Human Channelization

Diverting water out of rivers can cause drainages to merge or cause part of the flow to be directed into its own internal drain (Toshka Lakes on the Nile)