Chapter 3. Drainage

• term drainage describes river system of an area. Small streams flowing from different directions come together to form main river, which ultimately drains into a large water body such as a lake or a sea or an ocean.
Drainage Basin: area drained by a single river system is known as a drainage basin.
Water Divide: Any elevated area, such as a mountain or an upland that separates two drainage basins is called a water divide.

Drainage System in India
Indian rivers are divided into two major groups:
• Himalayan rivers
• Peninsular rivers

Himalayan Rivers Peninsular Rivers
(1) Most of Himalayan rivers are perennial which means they have water flow throughout year. Peninsular rivers are seasonal.
(2) These rivers receive water from rain as well as from melted snow from high mountains. flow of these rivers depend on rainfall.
(3) Two major Himalayan rivers, Indus & Brahmaputra originate from north of mountain ranges. Most of rivers of peninsular India originate in Western Ghats and flow towards Bay of Bengal.
(4) Himalayan rivers have long courses from their source to sea. These rivers have shorter and shallower courses as compared to Himalayan rivers.

Himalayan River System
major Himalayan rivers are Indus, Ganga & Brahmaputra. A river along with its tributaries is known as a river system.

Ganga River System
• source of Ganga known as ‘Bhagirathi’ is fed by Gangotri Glacier and joined by Alaknanda at Devaprayag in Uttarakhand.
• Ganga emerges from mountains on to plains at Haridwar.
• Ganga is joined by many tributaries from Himalayas, a few of them being major rivers, such as Yamuna, Ghaghara, Gandak & Kosi.
• length of Ganga is over 2500 km. Farakka in West Bengal is northernmost point of Ganga delta where Ganga river divides into 2 parts:
(1) Bhagirathi-Hooghly flows southwards through deltaic plains to Bay of Bengal.
(2) mainstream flows southwards into Bangladesh and is joined by Brahmaputra. Further downstream, it is called Meghna. Meghna River flows into Bay of Bengal and forms Sundarban Delta.

Indus River System
• Indus is one of longest rivers in world with a total length of 2900 km.
• river Indus rises in Tibet, near Lake Mansarowar. It enters India in Ladakh, where it forms a picturesque gorge.
• Satluj, Beas, Ravi, Chenab & Jhelum join together to enter Indus near Mithankot in Pakistan. Zaskar, Nubra, Shyok & Hunza join Indus in Kashmir region.

Brahmaputra River System
• Brahmaputra rises in Tibet east of Mansarowar lake. This is slightly longer than Indus. On reaching Namcha Barwa [7757m] it takes a ‘U’ turn and enters India in Arunachal Pradesh through a gorge, where it is known as Dihang. river shifts its channel frequently.
• Dihang is joined by, Lohit, & many other tributaries to form Brahmaputra in Assam.

Peninsular Rivers
• main water divide in Peninsular India is formed by Western Ghats. Most of major rivers of Peninsula, such as Mahanadi, Godavari, Krishna & Kaveri flow eastwards and drain into Bay of Bengal. These rivers make deltas at their mouths. Narmada and Tapi are only long rivers, which flow west and make estuaries.
(1) Narmada Basin
• Narmada rises in Amarkantak hills in Madhya Pradesh.
• Narmada flows through a deep gorge at ‘Marble rocks’ near Jabalpur.
• At Dhuadhar falls river jumps over steep rocks.
• Narmada basin covers parts of Madhya Pradesh and Gujarat.
(2) Tapi Basin
• Tapi rises in Satpura ranges, in Betul district of Madhya Pradesh. Its basin covers parts of Madhya Pradesh, Gujarat & Maharashtra.
(3) Mahanadi Basin
• Mahanadi rises in highlands of Chhattisgarh.
• length of river is about 860 km. Its drainage basin is shared by Maharashtra, Chhattisgarh, Jharkhand, and Odisha.
(4) Godavari Basin
• Godavari is largest Peninsular river. Its length is about 1500 km. It rises from slopes of Western Ghats in Nasik district of Maharashtra.
• basin covers parts of Maharashtra, Madhya Pradesh, Odisha & Andhra Pradesh.
• Godavari is joined by a number of tributaries, such as Purna, Wardha, Pranhita, Manjra, Wainganga & Penganga.
• Owing to its length and area it covers, it is called Dakshin Ganga.
(5) Krishna Basin
• It rises from a spring near Mahabaleshwar.
• length of river is about 1400 km. Tungabhadra, Koyana, Ghatprabha , Musi & Bhima are some of its main tributaries. Its drainage basin is shared by Maharashtra, Karnataka & Andhra Pradesh.
(6) Kaveri Basin
• Kaveri rises in Brahmagri range of Western Ghats.
• total length of river is about 760 km. main tributaries of this river are Amravati, Bhavani, Hemavati & Kabini. Its basin drains parts of Karnataka, Kerala & Tamil Nadu. river Kaveri makes second biggest waterfall in India, called Shivasamudram falls.
• Besides these major rivers, there are some smaller rivers flowing towards east. Some of them are:
(1) Damodar
(2) Brahmani
(3) Baitarni
(4) Subarnrekha

Role of Rivers in Economy
• Rivers have been of fundamental importance throughout human history.
• Water from rivers is a basic natural resource, essential for various human activities.
• Rivers are used for irrigation, navigation, hydropower generation.

River Pollution
• growing need for water in homes, cities, factories, and farms is affecting quality of river water. Rivers are getting dirty because a lot of untreated sewage and waste water from factories are being dumped into them. Concern about increasing pollution of rivers led to launch of several action plans [called Namami Gange mission] to clean them up.

• India has many lakes. These lakes differ from each other in size and other characteristics.
• Most lakes are permanent, Some contain water only during rainy season.
• Some lakes are result of action of glaciers and ice sheets.
• Some have been formed by wind, river action and human activities.
• These lakes are attractive to tourists in places like Srinagar, and Nainital.
• A meandering river across a floodplain forms cut-offs that later develops into ox-bow lakes.
• Spits and bars form lagoons in coastal areas. Eg: Chilika lake, Pulicat lake and Kolleru lake.
• Lakes in region of inland drainage are sometimes seasonal. For example, Sambhar Lake in Rajasthan is a salt water lake which is used for producing salt.
• Most of freshwater lakes are in Himalayan region. They are of glacial origin. Wular lake in Jammu and Kashmir is result of tectonic activity which is largest freshwater lake in India. Some other important freshwater lakes are Dal lake, Bhimtal, Nainital, Loktak & Barapani.

Importance of Lakes
• Lakes are useful to human beings in many ways:
(1) Lakes help to regulate flow of a river.
(2) During heavy rains, these lakes prevent flooding.
(3) During dry season, these lakes help to maintain an even flow of water.
(4) Lakes can be used for developing hydel power.
(5) They moderate surrounding climate, maintain aquatic ecosystem, enhance natural beauty, and provide recreation.

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