Drainage Systems in India

Drainage system explains the full river network and its area. Exam tip: study a river from source to mouth.

The direct answer is B: a water divide separates two drainage basins. A drainage basin is the area from which all water flows into one main river and its tributaries. A water divide is a higher ridge, hill, or elevated boundary; rainfall falling on its two sides flows into different river systems. Thus it acts like a boundary between neighbouring basins. Option B is correct because separation of drainage basins is the defining role of a water divide. Option A is wrong because a delta forms where a river deposits sediment near its mouth; a divide is usually found in higher land near the edges of basins. Option C is wrong because a divide does not keep a river away from the sea; rivers generally flow downhill and may ultimately reach the sea. Option D is wrong because pollution is caused by harmful substances and human activities, not by the natural boundary called a divide. Think of a roof ridge: water on one side runs one way and water on the other side runs another way. In an exam, connect water divide with basin boundary.

Himalayan rivers get water from snowmelt and rainfall. Exam tip: link perennial with water throughout the year.

Peninsular rivers depend more on rainfall. Exam tip: remember monsoon and river water together.

These five rivers are major rivers linked with the Indus system. Exam tip: remember Punjab rivers separately.

Bhagirathi and Alaknanda meet at Devprayag. Exam tip: remember this confluence for the beginning of the name Ganga.

Ganga and its tributaries deposit alluvial soil. Exam tip: connect alluvial soil with agriculture.

Yamuna meets the Ganga at Prayagraj. Exam tip: treat Yamuna as a major tributary of the Ganga system.

The Kosi is famous for floods and course shifting. Exam tip: remember it as a flood-prone river of the Ganga system.

The Brahmaputra is called Tsangpo in Tibet and Brahmaputra in India. Exam tip: remember the name with location.

In India, the Brahmaputra flows through the Assam Valley. Exam tip: connect Brahmaputra with north-eastern India.

Sundarbans Delta is linked with deposition by Ganga and Brahmaputra. Exam tip: connect delta with deposition.

Majuli is a famous river island associated with the Brahmaputra. Exam tip: remember Majuli with Assam and Brahmaputra.

Godavari is considered the longest river of Peninsular India. Exam tip: remember it by the name Dakshin Ganga.

These rivers flow eastward into the Bay of Bengal. Exam tip: remember east-flowing Peninsular rivers together.

Correct answer: B. Narmada and Tapi are important west-flowing Peninsular rivers. They flow through rift valleys and finally enter the Arabian Sea, unlike many major Peninsular rivers such as the Godavari, Krishna and Mahanadi, which generally flow eastward to the Bay of Bengal. A is incorrect because both Narmada and Tapi are Peninsular rivers, not Himalayan rivers. C is incorrect because they are independent river systems, not distributaries of the Ganga. D is incorrect because both rivers do reach the sea. The key comparison is direction and outlet: east-flowing rivers usually reach the Bay of Bengal, while Narmada and Tapi flow west to the Arabian Sea. This westward course is a distinctive drainage feature of the Peninsular plateau. Memory cue: “Narmada and Tapi take the westward route.”

Many west coast rivers have less deposition and more tidal influence. Exam tip: connect Narmada Tapi with estuaries.

Luni flows in Rajasthan and does not reach the sea. Exam tip: remember Luni as an example of inland drainage.

Dendritic pattern resembles branches of a tree. Exam tip: remember it as a common drainage pattern.

Direct answer: Option B is correct. A radial drainage pattern forms when streams flow outward in different directions from a central highland, dome, volcanic cone, or elevated area. The step-by-step idea is simple: the centre is high; gravity makes water move downslope; the slopes point away from the centre; separate streams therefore spread outward like the spokes of a wheel. Option A describes streams joining one mouth, not radial drainage. Option B states the defining condition. Option C is wrong because underground flow is not the defining arrangement of a radial pattern. Option D is wrong because the presence or absence of tributaries does not define radial drainage. Examples are drainage around some domes and volcanic cones. Memory cue: radial means rays moving away from a high centre.

In trellis pattern, tributaries join the main stream almost at right angles. Exam tip: treat it as structurally controlled pattern.

Rectangular pattern can develop under the control of rock structure. Exam tip: connect it with joints and faults.

Deposition dominates in a delta while tidal influence is important in an estuary. Exam tip: identify the process at river mouth.

A tributary adds water while a distributary branches away in delta region. Exam tip: identify both by flow direction.

In the upper course, river speed and slope can be greater. Exam tip: connect upper course with valley erosion.