Mist rises above River Rapti in the winter mornings at Chitwan National Park. Chitwan. by Nikki Thapa

Rapti in the east is a diminutive river that drains the Chitwan Valley and serves as the northern boundary of the Chitwan National Park, it converges with the Narayani River. The river traverses the Mahabharat Range and is fed by various tributaries viz Samari, Karra, Kukhreni, Reu, Panchand from the left, and Lothther and Manahari from the right.

The West Rapti River spans both Nepal and India and originates in the Mid-Western Region, it flows through the Awadh and Purwanchal regions of the Uttar Pradesh state in India. Ultimately, it merges with the Ghaghara, a significant left-bank tributary of the Ganges, known as Karnali in Nepal. The tributaries of the West Rapti are Lungri Khola, Jhimruk Khola, Ami River, and Rohini River, while Arun Khola contributes from the right.

This river holds historical significance, particularly for the Janajati ethnic groups of Nepal, and is called the "Airavati River" and serves as a tributary to the Sarayu, one of the sacred rivers in the Buddhist midland.

River Rapti flowing through the Chitwan National Park. Chitwan. by Nikki Thapa