The three important Himalayan rivers are the Ganga, the Brahmaputra and the Indus. The Indus originates in Tibet from lake Mansarovar. The main tributaries of Indus are the Satluj, the Beas, the Ravi, the Chenab and the Jhelum.
The Indus covers a distance of 2900 kilometres before reaching its destination. In 1960, Jawaharlal Nehru and Mohammed Ayyub Khan, the then President of Pakistan, signed a treaty known as the Indus Water Treaty. According to this treaty, India could use 20% of the total water carried by the Indus river system.
The river Ganga, is the longest river in India, and originates from the Gangotri glacier in the Himalayas. The Ganga starts off as the Bhagirathi, and is joined by the Alaknanda at Devaprayag. The major tributaries of Ganga are the Yamuna, the Ghaghara, the Gandak and the Kosi rivers. All these rivers originate in the Nepal Himalayas.
The peninsular tributaries that join the Ganga are the Chambal and the Betwa rivers. The interesting feature of the path of the Ganga from the Ambala water divide is that the river meanders a lot before reaching Sunderban. This is because the distance between Ambala and Sunderban is about 1800 kilometres. The slope along the path is very gentle, about one metre for every 6 kilometres. The flow of water is very slow, and as a result, the river develops large meanders.
Like the Indus, the Brahmaputra also starts in Tibet, from the east of the Mansarovar lake. The Brahmaputra river is slightly longer than the Indus, and flows its course eastwards, parallel to the Himalayas.
A major difference with the Ganga is that the Brahmaputra flows a course mostly outside of India. It enters India from Arunachal Pradesh through a gorge. The Brahmaputra gathers strength through its tributaries, the Dihang, the Dibang and the Lohit rivers.