Himalayas is source of five rivers which flow through Himachal Pradesh and provide abundance of water to the Indus-river basin. The Himalayan mountain chain has a dominant influence on the climatic conditions prevailing over Indian sub-continent. They lie in the path of rain-bearing monsoon winds and thus bring rain to a large part of India.
The drainage system of Himalaya is very complex. It is composed of both of rives and glaciers. In the Rig Veda, four out of the five rivers which flow through Himachal Pradesh, found mention, viz, Asikni (Chenab), Purushani (Ravi), Arjikiya (Beas), and Sutudri or Shatadru (Satluj). The fifth river Yamuna which rises from Yamunotri, has a mysthical relation to the sun. Today not only Punjab, but Himachal Pradesh is to be called the land of five rivers.
(a) Indus River System : The river Indus rises from the Tibetan plateau and enters the Himalaya in Ladakh. It enters the Kashmir region near its confluence with the river Gurtang, at an elevation of about 4200 mtrs. The drainage basin of the Indus river system extends from the Naga Parbat mass in the extreme Northern-Western part of the country to the Western slopes of the Shimla ridge in Himachal Pradesh.
It includes the whole of Jammu and Kashmir and most of the Himachal Pradesh. The extreme Northern tract of the Indus basin comprises of the cold deserts of Ladakh, Lahaul Spiti and Pooh. South of this tract lies the higher, Himalayan mountain wall. The lower and middle Himalayas occupy the central part of the Indus basin. The low rolling Shivalik hills occur along its Southern periphery.
Climatic conditions in the Indus river system vary from arctic to sub-tropical. The cold desert area remains devoid the rainfall and experiences heavy snowfall. The important rivers of this system are the Sutlej, the Beas, the Ravi, the Chenab and the Jhelum. Out of these five, four flow through Himachal Pradesh.
(b) Ganga River System : The drainage basin of the Ganga river system covers about one third of the Western Himalaya and the entire Central Himalaya. This basin extends from the Eastern face of the Shimla ridge in Himachal Pradesh to the South Western slopes of the Kanchanjunga massif on the Nepal Sikkim border, thereby including parts of Kinnaur, Shimla, Solan and Sirmaur district of Himachal and Garhwal, Kumaun and Nepal.
The Ganga is the most sacred river of India. The story off the Ganga from her source to sea, from ancient times to the modern period is the story of India’s civilization and culture. The Ganga has its source near Gomukh glacier, near Ganggotri (Uttrakhand). The Ganga is formed by two head streams namely Alaknanda and Bhagirathi. It enters the plains near Haridwar. The Yamuna meets this river at Allahabad known as Sangam. The Ganga is the master stream of the area. South of Farakka, the river divides into a number of channels to form ‘Sunder Ban Delta’ (Largest in the world). The main tributaries of the Ganga system are the Yamuna, Bhagirathi and Alaknanda, Kali and its tributaries, the Ghahra, the Gandak and the Kosi river. The important settlements between the bank are – Haridwar, Kanpur, Allahabad, Varanasi, Patna and Calcutta.