Drainage System

Introduction

What is a Drainage System?

A drainage system refers to the entire network of rivers, streams, and other water bodies that collect and transport surface water to a larger water body, such as an ocean, sea, or lake. It is influenced by topography, geological structures, climate, and human activities.

Importance of Drainage Systems

• Supports Agriculture – Rivers provide irrigation and fertile alluvial soil.
• Drinking Water Source – Major rivers supply water for domestic and industrial use.
• Hydroelectric Power – Rivers help in electricity generation (e.g., Bhakra Nangal Dam on the Sutlej).
• Navigation and Transport – Historically, rivers served as trade routes (e.g., Ganga and Brahmaputra).
• Ecological Significance – Supports biodiversity and ecosystems (e.g., Sundarbans mangroves).

2. Major Drainage Basins of India

A drainage basin (also called a catchment area) is the area from which a river and its tributaries collect water.

Major River Basins in India

River Basin	Major Rivers	States Covered	Drainage Area (sq. km)
Indus Basin	Indus, Jhelum, Chenab, Ravi, Beas, Sutlej	J&K, Punjab, Himachal Pradesh, Haryana	~1.2 million
Ganga Basin	Ganga, Yamuna, Ghaghara, Gandak, Kosi	Uttarakhand, UP, Bihar, West Bengal	~1.1 million
Brahmaputra Basin	Brahmaputra, Dibang, Lohit, Subansiri	Arunachal Pradesh, Assam, Nagaland	~580,000
Godavari Basin	Godavari, Indravati, Pranhita, Sabari	Maharashtra, Telangana, Andhra Pradesh	~312,000
Krishna Basin	Krishna, Tungabhadra, Bhima	Maharashtra, Karnataka, Andhra Pradesh	~258,000
Mahanadi Basin	Mahanadi, Seonath, Jonk	Chhattisgarh, Odisha	~141,600
Kaveri Basin	Kaveri, Kabini, Bhavani	Karnataka, Tamil Nadu	~81,155

3. Classification of Rivers in India

India’s rivers are broadly classified into two categories:

A. Himalayan Rivers

These rivers originate in the Himalayan region and are perennial, meaning they flow throughout the year due to glacial melt and monsoon rainfall.

Characteristics of Himalayan Rivers:

1. Perennial in Nature – Flow continues even in dry seasons.
2. High Erosion Capability – Due to steep slopes and heavy water discharge.
3. Long and Large Basins – Cover extensive areas (e.g., Ganga and Brahmaputra).
4. Tend to Meander in Plains – Rivers like the Ganga form bends due to deposition.
5. Delta Formation at Mouth – Large alluvial deltas (e.g., Sundarbans).

Major Himalayan River Systems:

1. Indus River System

• Origin – Mansarovar Lake, Tibet
• Entry into India – Ladakh region, J&K
• Major Tributaries – Jhelum, Chenab, Ravi, Beas, Sutlej
• Indus Water Treaty (1960) – India gets 20% of water, Pakistan gets 80%
• Example – The Sutlej supports the Bhakra Nangal Hydroelectric Project.

2. Ganga River System

• Origin – Gangotri Glacier, Uttarakhand (as Bhagirathi River)
• Joins Alaknanda at Devprayag → Forms the Ganga
• Major Tributaries – Yamuna, Ghaghara, Gandak, Kosi, Son
• Example – Sundarbans Delta (West Bengal) is the largest in the world.

3. Brahmaputra River System

• Origin – Mansarovar Lake, Tibet (as Tsangpo River)
• Enters India – Arunachal Pradesh (as Dihang)
• Major Tributaries – Dibang, Lohit, Subansiri
• Example – Causes severe floods in Assam due to high sediment load.

B. Peninsular Rivers

These rivers originate from the Western Ghats, Vindhyas, or Deccan Plateau and are seasonal in nature.

Characteristics of Peninsular Rivers:

1. Non-Perennial Flow – Depend on monsoon rainfall.
2. Flow Through Hard Rock Terrain – Less meandering than Himalayan rivers.
3. Shorter in Length – Comparatively smaller basins.
4. Delta and Estuary Formation – East-flowing rivers form deltas, west-flowing rivers form estuaries.

Major Peninsular River Systems:

1. Godavari River System

• Longest Peninsular River (1,465 km)
• Origin – Trimbak Plateau, Maharashtra
• Tributaries – Indravati, Manjira, Pranhita, Sabari
• Example – Polavaram Irrigation Project (Andhra Pradesh).

2. Krishna River System

• Origin – Mahabaleshwar, Maharashtra
• Tributaries – Tungabhadra, Bhima, Ghataprabha
• Example – Almatti Dam (Karnataka).

3. Mahanadi River System

• Origin – Chhattisgarh Highlands
• Tributaries – Seonath, Jonk
• Example – Hirakud Dam (Odisha).

4. Kaveri River System

• Origin – Talakaveri, Karnataka
• Example – Kaveri Water Dispute between TamilNadu & Karnataka.

4. Drainage Patterns in India

Types of Drainage Patterns:

1. Dendritic Drainage – Tree-like pattern (e.g., Ganga, Yamuna).
2. Trellis Drainage – Parallel tributaries meeting at right angles (e.g., Godavari).
3. Radial Drainage – Outward flow from a central point (e.g., Amarkantak Plateau – Narmada, Son).
4. Centripetal Drainage – Rivers flow into a central depression (e.g., Sambhar Lake, Rajasthan).

5. River Water Disputes in India

Dispute	States Involved	Issue
Cauvery Water Dispute	Tamil Nadu & Karnataka	Water sharing
Krishna Water Dispute	Maharashtra, Karnataka, Andhra Pradesh, Telangana	Allocation
Ravi-Beas Dispute	Punjab & Haryana	River distribution

6. Conclusion

India’s drainage system plays a critical role in agriculture, water resources, hydropower, and ecological balance. Understanding river systems is essential for UPSC aspirants, as it connects to geography, economy, climate, and water disputes.

MCQ Practice 

1. Consider the following statements regarding the Himalayan Rivers:

1. They are perennial in nature and are fed by both glacial melt and monsoon rainfall.
2. These rivers generally form estuaries at their mouths.
3. They exhibit high erosion capability due to steep slopes.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 1 and 3 only

(c) 2 and 3 only

(d) 1, 2, and 3

Answer: (b) 1 and 3 only

2. Consider the following statements regarding the Ganga River System:

1. The Ganga originates from the Gangotri Glacier in Uttarakhand as the Bhagirathi River.
2. The Yamuna is the only tributary of the Ganga.
3. The Sundarbans Delta, formed by the Ganga and Brahmaputra, is the largest in the world.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2, and 3

Answer: (c) 1 and 3 only

3. With reference to the Indus Water Treaty (1960), consider the following statements:

1. It was signed between India and Pakistan with the mediation of the World Bank.
2. Under the treaty, India gets 80% of the total Indus river water while Pakistan gets 20%.
3. The major tributaries of the Indus include Jhelum, Chenab, Ravi, Beas, and Sutlej.

Which of the statements given above are correct?

(a) 1 and 3 only

(b) 2 and 3 only

(c) 1 and 2 only

(d) 1, 2, and 3

Answer: (a) 1 and 3 only

4. Consider the following pairs of major Peninsular rivers and their tributaries:

River	Tributary
1. Godavari	Indravati
2. Krishna	Bhima
3. Mahanadi	Kabini
4. Kaveri	Sabari

Which of the pairs given above are correctly matched?

(a) 1 and 3 only

(b) 1 and 2 only

(c) 1, 2, and 4 only

(d) 1, 2, 3, and 4

Answer: (b) 1 and 2 only

(Note: Kabini is a tributary of Kaveri, and Sabari is a tributary of Godavari.)

5. Which of the following rivers flow westward and form estuaries instead of deltas?

1. Narmada
2. Godavari
3. Krishna
4. Tapi

Select the correct answer using the code given below:

(a) 1 , 2 and 4 only

(b) 2 and 3 only

(c) 1, 2, and 4 only

(d) 1 and 4 only

Answer: (d) 1 and 4 only

6. Consider the following statements regarding drainage patterns in India:

1. A trellis drainage pattern is formed when tributaries join the main river at acute angles.
2. The dendritic pattern resembles the shape of a tree and is commonly seen in the Ganga river system.
3. The radial drainage pattern is formed when rivers flow outward from a central point, such as the Amarkantak Plateau.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2, and 3

Answer: (b) 2 and 3 only

(Note: In a trellis drainage pattern, tributaries join the main river at right angles, not acute angles.)

7. Which of the following correctly describes the characteristics of Peninsular rivers in India?

1. They are non-perennial and largely dependent on monsoon rainfall.
2. They flow through hard rock terrain and exhibit less meandering.
3. Most of them form large alluvial deltas at their mouths.

Select the correct answer using the code given below:

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2, and 3

Answer: (d) 1, 2, and 3

8. With reference to river water disputes in India, consider the following pairs:

Dispute	States Involved
1. Cauvery Water Dispute	Tamil Nadu & Karnataka
2. Krishna Water Dispute	Gujarat & Maharashtra
3. Ravi-Beas Dispute	Punjab & Haryana

Which of the pairs given above are correctly matched?

(a) 1 and 3 only

(b) 2 and 3 only

(c) 1 and 2 only

(d) 1, 2, and 3

Answer: (a) 1 and 3 only

(Note: The Krishna Water Dispute involves Maharashtra, Karnataka, Andhra Pradesh, and Telangana, not Gujarat.)

9. Which of the following statements about the Brahmaputra River System is/are correct?

1. It originates in Tibet as the Tsangpo River.
2. The river enters India through Arunachal Pradesh and is known as the Dihang before becoming the Brahmaputra.
3. The Brahmaputra carries a low sediment load and does not cause floods in Assam.

Select the correct answer using the code given below:

(a) 1 and 3 only

(b) 2 and 3 only

(c) 1 and 2 only

(d) 1, 2, and 3

Answer: (c) 1 and 2 only

(Note: The Brahmaputra carries a very high sediment load and frequently causes floods in Assam.)

10. Consider the following statements regarding the role of drainage systems in India:

1. Rivers provide fertile alluvial soil, which is beneficial for agriculture.
2. Many rivers support hydroelectric projects, aiding power generation.
3. The drainage system has no role in biodiversity conservation.

Which of the statements given above are correct?

(a) 1 and 2 only

(b) 2 and 3 only

(c) 1 and 3 only

(d) 1, 2, and 3

Answer: (a) 1 and 2 only