Budhi gandak is an important river but the other river by name GANDAK is much bigger river origineting from Himalyas in Nepal.The Gandak enters in India at the border of states of Bihar(W.Champaran Distt.) and Uttar Pradesh(Gorakhpur Distt.) and flows through East Champaran,Siwan Chhapra and into river Ganges At Hajipur(Vaishali Distt.) near Patna. Budhi gandak originates From W.Champaran near Ramnagar and Bagaha ,passes through various districts of Bihar( East Champaran , Mujaffarpur, Samastipur,Khagaria) and flows into river Ganges near Khagaria/Manasi.(sahsn@indiatimes.)