The Rohni or Rohini River rises in the Chure or Siwalik Hills in Kapilvastu and Rupandehi Districts of Nepal's Lumbini Zone and flows south into Uttar Pradesh state, India. At Gorakhpur it becomes a left bank tributary of West Rapti River, which in turn joins the Ghāghara above Gaura Barhaj, then Ghaghara in turn joins the Ganges.

According to an account in several Buddhist texts, Kapilavatthu the town of the Sakyans and Koliya the town of the Kolyanswere situated on either side of the Rohini river. The cultivators of both towns worked the fields watered by the Rohini river. One year, they did not have enough rain and finding that the paddy and other crops were beginning to shrivel up, cultivators on both sides wanted to divert the water from the Rohini river to their own fields. Those living in Koliya said that there was not enough water in the river for both sides, and that if only they could channel the water just once more to their fields that would be enough for the paddy to mature and ripen. On the other hand, people from Kapilavatthu argued that, in that case, they would be denied the use of the water and their crops would surely fail, and they would be compelled to buy from other people. They said that they were not prepared to go carrying their money and valuables to the opposite bank of the river in exchange for food. Both sides wanted the water for their own use only and there was much ill will between them due to abusive language and accusations on both sides. The quarrel that started between the cultivators came to the ears of the ministers concerned, and they reported the matter to their respective rulers, and both sides prepared to go to war.