Ganga river system: origin, course, tributaries and states
The Ganga rises at Gangotri, meets the Alaknanda at Devprayag, and flows about 2,525 km to the Bay of Bengal. Learn its main tributaries, the states it crosses, and why its basin matters.
The Ganga river system begins where the Bhagirathi, flowing from the Gangotri Glacier, meets the Alaknanda at Devprayag in Uttarakhand, and runs about 2,525 km through Uttarakhand, Uttar Pradesh, Bihar and West Bengal to the Bay of Bengal, fed by major tributaries such as the Yamuna, Ghaghara, Gandak, Kosi and Son.
Origin: two Himalayan streams become the Ganga
The Ganga does not start as a single stream. Its headstream, the Bhagirathi, rises at Gaumukh at the foot of the Gangotri Glacier in Uttarakhand, while the Alaknanda rises from glaciers near Satopanth and Bhagirath Kharak. The two meet at Devprayag, and from that confluence the river is called the Ganga.
From the hills the young river cuts through narrow gorges, then enters the northern plains at Haridwar. Himalayan rivers like the Ganga flow all year, fed by glacier melt in the dry months and by monsoon rain in summer, which is why they are called perennial rivers.
Course: from the Himalaya to the delta
Across the plains the Ganga flows past Haridwar, Kanpur, Prayagraj, Varanasi and Patna, gathering tributaries and spreading fertile silt over a wide floodplain. Its course is gentle here, so the river meanders and shifts channels over time.
Near Farakka in West Bengal, a barrage diverts part of the flow into the Bhagirathi-Hooghly channel, which flows past Kolkata. The main stream continues into Bangladesh, where it is called the Padma, and finally reaches the Bay of Bengal through the Sundarbans delta, a tide-dominated landscape of mangrove creeks.
Tributaries: left bank and right bank
The Ganga's left-bank tributaries, joining from the north, are the Ramganga, Gomti, Ghaghara, Gandak, Kosi and Mahananda. Its right-bank tributaries, joining from the south, include the Yamuna, Son and Punpun. Remembering the banks this way is a standard exam shortcut.
The Yamuna is the standout: it rises at the Yamunotri Glacier, passes Delhi, Mathura and Agra, and meets the Ganga at Prayagraj after about 1,376 km. Other major tributaries include the Son, which rises on the Amarkantak Plateau and runs about 784 km, the Ghaghara, which flows from near Mansarovar in Tibet for about 1,080 km, and the Kosi, which comes down from Nepal for about 729 km and is known for changing course and causing floods in Bihar.
Why the basin matters
The Ganga basin covers around 8.6 lakh sq km in India, making it the country's largest river basin, and its alluvial plains support rice, wheat, sugarcane and pulses for one of the most densely populated regions on Earth. The river is also a transport route: National Waterway-1 runs on the Ganga.
The basin's wildlife includes the endangered Ganges river dolphin. At the same time the river faces heavy pressure from sewage, industrial waste and urban runoff, and the government's Namami Gange programme aims to cut pollution, treat sewage and protect the river's biodiversity.
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Frequently asked questions
Where does the Ganga originate?
The Ganga takes shape at Devprayag in Uttarakhand, where the Bhagirathi, which rises at Gaumukh near the Gangotri Glacier, meets the Alaknanda, which rises from glaciers near Satopanth and Bhagirath Kharak.
What is the length of the Ganga river?
The Ganga is commonly cited as about 2,525 km long. Some sources give slightly different totals, because river length depends on where the source and the end of the main channel are measured.
Which is the largest tributary of the Ganga?
The Yamuna is the largest tributary of the Ganga. It rises from the Yamunotri Glacier, flows about 1,376 km, and joins the Ganga at Prayagraj, a meeting point known as the Triveni Sangam.
Which are the left bank tributaries of the Ganga?
The main left-bank tributaries are the Ramganga, Gomti, Ghaghara, Gandak, Kosi and Mahananda. The main right-bank tributaries are the Yamuna, Son and Punpun. Left and right are counted while facing downstream, in the direction the river flows.
Where does the Ganga meet the Bay of Bengal?
After the Farakka Barrage, the Bhagirathi-Hooghly distributary flows past Kolkata, while the main stream continues into Bangladesh as the Padma. The system ends in the Sundarbans delta and the Bay of Bengal.