The Karnali rises in the northern slopes of the Himalayas in Tibet, in the glaciers of Mapchachungo, at an elevation of about 3,962 metres (12,999 ft) above sea level.

[4] Cutting southward across the Sivalik Hills, it splits into two branches, the Geruwa on the left and Kauriala river on the right near Chisapani to rejoin south of the Indian border and form the proper Ghaghara.

It flows southeast through Uttar Pradesh and Bihar states to join the Ganges downstream of the town of Chhapra, after a course of 1,080 kilometres (670 mi).

Now a 900 MW project is going to be constructed in this river In India, the administrative districts in the Ghaghra catchment are Ambedkar Nagar, Ayodhya, Gonda, Azamgarh, Barabanki, Basti, Ballia, Bahraich, Deoria, Gonda, Gorakhpur, Sant Kabir Nagar, Lakhimpur Kheri, Mau, Sitapur of Uttar Pradesh and Siwan district in Bihar.

[2] Bardia National Park is the largest and most undisturbed protected area in the Karnali River basin, covering 968 km2 (374 sq mi) on the southern slopes of the Sivalik Hills.

At Chisapani Gorge, the swift-flowing Karnali River emerges from the Shiwalik Range onto the broad plain and flows purposefully through the semi-tropical jungle.

The park is famous for two Asian elephant herds, several deer species, gaur, nilgai, Himalayan tahr, serow and goral.

The Karnali supports the endangered mugger crocodile, the gharial, a few remaining South Asian river dolphins and the golden mahseer.

The Karnali provides the upper range for the Gangetic river dolphin (Platanista gangetica), the largest freshwater mammals found on the Indian subcontinent.

They are often found in places where human activities are most intense and they are sometimes accidentally caught by the local people who live in the lower Karnali basin.

These dolphins are at their farthest upstream range and isolated by the Girijapuri Barrage (a low gated dam), located about 16 kilometres (10 mi) downstream of the Nepal–India border ( in Mihinpurwa district Bahraich).

Disturbance and environmental degradation associated with geotechnical feasibility studies and bridge and road construction for the dam already may have contributed to a decline in the number and range of dolphins or susu above the Nepal-India border.

The feeder channel taking off from the Lower Sarda Barrage is 258.8 kilometres (160.8 mi) long, feeds the five branches of Dariyabad, Barabani, Haideganj, RaeBareil and Purva, and is designed to carry a discharge of 765 cubic metres per second (27,000 cu ft/s).

Apart from in the foothills of the Himalayas where most of the streams were simply fast-moving water throughout the greater part of the year and not navigable when flowing rapidly, most of the rivers with steadier currents had boats on them.

With the exception of eastern parts of Bengal where abundance of water in the natural network of channels sustained and continued to provide a suitable mode of transport of goods and people, the railways had almost entirely replaced the waterways as communication lines throughout the country by the end of the 19th century.

There is a great urgency to carry out detailed study of the Karnali river to develop modern inland waterway by applying various channel improvement technologies.

According to the legend, Urmila, wife of Lakshmana, performed samadhi by drowning herself on the banks of the river Sarju, and it is believed that her soul attained salvation at Rama's feet.