The
Gowd-i zerrah", i.e., Zerrah Depression (
Persian for "lake depression") is the lowest part of an inland
drainage basin covering large parts of southern
Afghanistan and
Iran known as the
Sistan Basin. The Sistan Basin is an
endorheic basin and encompasses a complex system of rivers, shallow lakes, marshes and wetlands as its
watershed, draining into the
Hamun Lakes in southeastern Iran. Occasional outflows from these lakes are carried back into Afghanistan by the seasonal Shile river to the basin's terminus, the Godzareh depression in Afghanistan. The
depression is flat and very shallow with fine textured
sediment at its lowest portions. The lowest section of the Godzareh depression is 467 m above sea level. The depression only receives
runoff water when the main tributaries are overflowing every 10 years on the average.