It drains a tract of 180 miles long by 150 broad before bursting through the Elburz mountain chain, and descending upon the low country which skirts the Caspian.

Rising in Persian Kurdistan almost from the foot of Zagros, it runs in a meandering course with a general direction of north-east through that province into the district of Khamseh, where it suddenly sweeps round and flows in a bold curve at the foot of lofty and precipitous rocks, first northwest and then north, nearly to Miana, when it doubles back upon itself, and turning the flank of the Zenjan range runs with a course nearly south-east to Menjil, after which it resumes its original direction of north-east, and, rushing down the pass of Budbar, crosses Ghilan to the Caspian.

Though its source is in direct distance no more than 320 miles from its mouth, its entire length, owing to its numerous curves and meanders, is estimated at 490 miles.

It is a considerable stream, forded with difficulty, even in the dry season, as high up as Karagul, and crossed by a bridge of three wide arches before its junction with the Garongu river near Miana.

In spring and early summer it is an impetuous torrent, and can only be forded within a short distance of its source.
The Jaghetu and the Aji-Su are the two chief rivers of the Urumiyeh basin.