Once one of the largest lakes in the world, it has shrunk considerably over the last 40 years. In the 1960s it had an area of more than 26,000 km². By 2000 it had fallen to less than 1,500 km². This is due to reduced rainfall combined with greatly increased amounts of irrigation water being drawn from the lake and the rivers which feed it, the largest being the Chari/Logon system. Because it is very shallow - only 7 metres at its deepest - its area is particularly sensitive to small changes in average depth, and it consequently also shows seasonal fluctuations in size.