Lake Chad Evaporation 1973 to 1987

Located on the edge of the Sahara and bordering four countries—Chad, Cameroon, Nigeria, and Niger—the immense area of this land locked lake has nearly disappeared in recent years. Persistent drought has caused the lake to drop from its former sixth place position in the list of world's largest lakes; it is now one tenth its former size.

The basin of the lake is not naturally deep, so the surface area of the lake tended to spread out, keeping the total depth to little more 23 feet (7 meters). In recent years, rainfall patterns have begun to change, and tributaries to Lake Chad have not been refilling the basin as rapidly as they used to. The lush, productive flora and fauna fed by the wetlands of the shallow lake have suffered as a result.

This has led to significant changes for various communities of people that live in the vicinity of the Lake. While for some the now exposed lake bed has enabled new land to be cultivated, much of the available fresh water that might have been used for irrigation is no longer dependable. As rainfall rates appear to be declining year after year, people living nearby develop even greater dependence on the lake, draining it even faster.

See http://svs.gsfc.nasa.gov/stories/earthday2001/index.html