Jaldhak or Dichu originates from the Kupup Lake, a small glacial lake in Sikkim. It gains volume through the confluence of two other streams near Bindu, viz., Bindu Khola and Dudh Pokhri. The combined stream meet at Bindu to increase the volume of Jaldhaka River, thus forming a riverine boundary with India and Bhutan in the left bank. The main tributaries that join the river on its right bank are the Murti, the Jholung khola, the Naksal Khola, the Sutunga and the Jarda in the lower reach. The Diana, Rehti-Duduya and Mujnai are the main left bank tributaries.
Jaldhaka River at the Nakshal Picnic Ground, India - Bhutan Border
The river flows through the three North Bengal districts of Kalimpong, Jalpaiguri and Cooch Bihar. The entire watershed is the most fertile agricultural zone along with the Teesta Basin. The upper course is famous for crops like ginger, medicinal herbs and fruits like oranges and pomegranate. The middle course comprising Jalpaiguri district is entirely tea and corn dominated and the lower course is dominated by rice, jute and tobacco. The inter-river formed lands are cultivated with crops like bamboo and mat sticks. In the lower basin, the inter-river lands are cultivated with banana.
The river enters Bangladesh at Ghoksadanga district to meet the Brahmaputra or the Jamuna as it is known there.
Floods
River Jaldhaka, along with River Teesta have caused major flooding multiple times in Bangladesh during monsoon season between June and September.