The correct sequence of the tributaries joining the Ganga from West to East is Gomati - Ghaghara - Gandak - Kosi.

Gomati: It is a plains-fed river that originates from Gomat Taal (Fulhaar Jheel) in the Pilibhit district of Uttar Pradesh. It joins the Ganga near Varanasi.

Ghaghara: It originates in the Mapchachungo glaciers near Mansarovar in Tibet. It flows through Nepal before joining the Ganga at Chhapra, Bihar.

Gandak: It rises in the Nepal Himalayas between the Dhaulagiri and Mount Everest. It enters the Ganga plain in Bihar and joins the Ganga at Sonpur near Patna.

Kosi: Known as the 'Sorrow of Bihar', it originates in the Himalayas (Tibet/Nepal) and joins the Ganga near Kursela in the Katihar district of Bihar.