In the northern portion of the delta, channels fill in between sand dunes during the flood season. Temporary lakes also fill during high floods. The water reaching these lakes is not returned to the river as flood waters recede.
The north receives far less precipitation than the southern portion. The mean annual precipitation there is just 200 mm (7.9 inches).
(Black stripes run through the 2011 image because of the Scan Line Corrector failure on Landsat 7 in May 2003.)