The Kamala originates from Churia Range near Maithan which is near Sindhuliagarhi in Sindhuli District of Nepal at an elevation of 1,200 metres (3,900 ft).[1][2] It flows in a southerly direction crossing Kamala Khoj area and after passing through a gorge above Chauphat it flows into the terai area of Nepal at Chisapani.[2]The Kamala forms the border between Siraha and Dhanusa districts in the terai. During the monsoon the river swells up and thus causes devastating river bank erosion.[3] Tao River and Baijnath Khola River merges with Kamala at Maini[4]
It enters Indian territory in Madhubani district in Bihar, 3.5 kilometres (2.2 mi) upstream of Jainagar. A barrage known as Kamala barrage has been constructed by the State Government near Jainagar. It joins the river Kareh (Bagmati) at Badlaghat in Khagaria district[1] and the combined stream flows into the Koshinearby. While one of its branches leads to the Bagmati another leads to the Kosi.[4]
In the lower reaches it follows the course of the Balan and is therefore also known as Kamala-Balan.