The Territorial disputes of India and Nepal include Kalapani, Nepal claims that the river to the west of Kalapani is the main Kali river, hence it belongs to Nepal. But India insists that the river to the east of Kalapani is the main Kali river, and therefore claim the Kalapani area belongs to India. The river borders the Nepalese zone of Mahakali and the Indian state of Uttarakhand. The Sugauli Treaty signed by Nepal and British India in 4 March 1816 locates the Kali River as Nepal's western boundary with India. Subsequent maps drawn by British surveyors show the source of the boundary river at different places. This discrepancy in locating the source of the river led to boundary disputes between India and Nepal, with each country producing maps supporting their own claims. The Kali River runs through an area that includes a disputed area of about 400 km² around the source of the river although the exact size of the disputed area varies from source to source. Kalapani has been occupied by India's Indo-Tibetan border security forces since the Sino-Indian War with China in 1962.