Gangtok District is an administrative district of the Indian state of Sikkim. It was renamed in 2021 as a result of administrative reorganisation of the state, which also saw three subdivisions of the East Sikkim district spawned off as a separate Pakyong district.

The Jaldhaka River (Pron:/ˌdʒælˈdɑːkə/), also known as Dichu, is a tributary of the Brahmaputra and a trans-boundary river flowing through India, Bhutan and Bangladesh with a length of 233 kilometres. It originates from the Bitang Lake at Kupup, Gangtok District, Sikkim, near the Jelep La pass below Dongkya Mountain Range. It flows through Pakyong District of Sikkim, India and then passes through forests of Samtse District of Bhutan where it flows for around 40 kilometres and than re-enters India at Bindu, Kalimpong district. Further it passes through Neora Valley National Park, Chapramari Wildlife Sanctuary and Gorumara National Park in West Bengal along with cities and towns, like Paren, Gairibas, Jhalong, Dhupguri, Falakata, Mathabhanga and flows through Kalimpong, Jalpaiguri and Cooch Behar districts in West Bengal, India before entering Bangladesh at Mogolhat, Lalmonirhat District of Rangpur Division. It is known as Dharla River in Bangladesh and flows through towns like Kolaghat, Phulbari and Kurigram City and Passes southwards until the Dharla debouches into the Brahmaputra River at Bagua Anantpur of Kurigram District. Due to the river's wandering over several international borders, only a small length of the river lies in Bangladesh and Bhutan and most of its path lies in India. In some places, this river is also known as Mansai river and Singhimari river.