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Drainage: The river system of an area is called drainage. The area drained by a single river system is called the drainage basin.
Depending on the slope of land, underlying rock structure and climate of an area, the streams in a drainage basin form certain patters. Different types of drainage pattern are as follows:
(1) Dendritic Drainage Pattern, (2) Trellis Drainage Pattern, (3) Rectangular Drainage Pattern, (4) Radial Drainage Pattern
- Dendritic Drainage Pattern: When the river channel follows the slope of the terrain, it develops dendritic pattern. The stream and its tributaries resemble the branches of a tree. Hence, it is called dendritic pattern.
- Trellis Drainage Pattern: When a river is joined by its tributaries at almost right angles, it develops a trellis pattern. Trellis pattern develops where hard and soft rocks exist parallel to each other.
- Rectangular Drainage Pattern: When rocks are strongly joined, then rectangular pattern develops.
- Radial Drainage Pattern: When the streams flow in different directions from a central peak or dome like structure, a radial pattern is developed.
It is important to note that a combination of different patterns may develop in the same drainage basin.
The drainage systems in India can be divided into two major groups, viz. the Himalayan Rivers and the Peninsular Rivers.
The Himalayan Rivers:
Most of the Himalayan Rivers are perennial, i.e. they have water throughout the year.
A river along with its tributaries forms a river system. There are three river systems in the Himalayas, viz. Indus, Ganga and Brahmaputra River Systems.
The Indus River System
- The river Indus originates in Tibet; near Lake Mansarowar. It enters India in the Ladakh district of Jammu & Kashmir.
- Zaskar, Nubra, Shyok and Hunza are the main tributaries which join the Indus in Kashmir region.
- After flowing through Baltistan and Gilgit, the Indus emerges from the mountains at Attock.
- Sutlej, Beas, Ravi, Chenab and Jhelum join together and enter the Indus near Mithankot in Pakistan. After that, the Indus flows southwards and finally reaches the Arabian Sea, east of Karachi.
- Indus is 2900 km long. The Indus plain has a very gentle slope. A little over one-third of the Indus basin is located in India; in the states of Jammu & Kashmir, Himachal Pradesh and Punjab. The rest of the portion is in Pakistan.