Himalayan River Evolution & Plains Formation

• While entering plains, rivers create flat valleys, ox-bow lakes, flood plains, braided channels, and deltas.
• In the Himalayas, river courses are tortuous, but they meander and shift frequently in the plains.
• The Kosi River, known as the 'sorrow of Bihar,' frequently changes its course.
• The Kosi carries much sediment from upper reaches, which gets deposited in the plains, blocking the course and causing the river to change course.

Evolution of the Himalayan Drainage

• There are differing opinions on the evolution of Himalayan rivers.
• Geologists believe a large river called Shiwalik or Indo-Brahma once flowed from Assam to Punjab and then to Sind, emptying into the Gulf of Sind near lower Punjab during the Miocene period (5-24 million years ago).
• The continuity of the Shiwalik formation and its lacustrine and alluvial deposits support this idea.
• The Indo-Brahma river is believed to have split into three main drainage systems: the Indus and its tributaries in the west, the Ganga and its Himalayan tributaries in the center, and the Brahmaputra in Assam and its Himalayan tributaries in the east.
• The split was likely caused by the Pleistocene upheaval in the western Himalayas.
• The Potwar Plateau (Delhi Ridge) became the water divide between the Indus and Ganga systems.
• The down-thrusting of the Malda gap between the Rajmahal hills and the Meghalaya plateau during the mid-Pleistocene diverted the Ganga and Brahmaputra towards the Bay of Bengal.

The River Systems of the Himalayan Drainage

• The Himalayan drainage includes several river systems.

The Indus System

• The Indus is one of the world's largest river basins, covering 11,65,000 sq km (321,289 sq km in India) with a total length of 2,880 km (1,114 km in India).
• The Indus, also known as the Sindhu, is the westernmost Himalayan river in India.
• It originates from a glacier near Bokhar Chu (31°15′ N latitude and 81°40′ E longitude) in the Tibetan region at 4,164 m altitude in the Kailash Mountain range.
• In Tibet, it is called 'Singi Khamban' (Lion's mouth).
• Flowing northwest between the Ladakh and Zaskar ranges, it passes through Ladakh and Baltistan.
• It cuts across the Ladakh range, forming a gorge near Gilgit in Jammu and Kashmir, entering Pakistan near Chilas in the Dardistan region.
• The Indus receives Himalayan tributaries like the Shyok, Gilgit, Zaskar, Hunza, Nubra, Shigar, Gasting, and Dras.
• It emerges from the hills near Attock and receives the Kabul River on its right bank.
• Other right bank tributaries include the Khurram, Tochi, Gomal, Viboa, and Sangar, originating in the Sulaiman ranges.
• The Indus flows southward and receives the 'Panjnad' above Mithankot.
• The Panjnad is formed by the five rivers of Punjab: the Satluj, Beas, Ravi, Chenab, and Jhelum.
• It finally discharges into the ocean.