A large part of the basin is so dry as to be considered a desert.

By the early 1960s many of the native species were no longer present in the northern part of the basin.

As a result, precipitation amounts over these parts of the basin are larger in winter than those given above.

The central part of the basin is covered by smooth plains material.

The smaller, southern part of the basin falls almost exclusively in Chad.

At times, parts of the basin were below the sea.

The tributary river systems in this part of the basin are small.

It is a major source of natural gas in the northern part of the basin.

It forms in the marine part of the basin during the base level fall.

The plan would leave huge parts of the 1.9-million-square-mile basin vulnerable to further exploitation.