### **Chapter 3 – Drainage (Rivers and Water Systems of India)**
#### 1. Meaning of Drainage
* The river system of an area is called **drainage**.
* A drainage basin is an area drained by a river and its tributaries.
* The world's largest drainage basin is the **Amazon River** in South America.
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#### 2. Drainage Systems of India
India has two main drainage systems:
1. **The Himalayan Rivers**
2. **The Peninsular Rivers**
These are different due to **geological structure**, **origin**, and **water availability**.
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#### 3. The Himalayan Rivers
* **Perennial rivers** (flow throughout the year, fed by both rain and glaciers).
* Have long courses, deep valleys, and form fertile plains and deltas.
* **Major river systems:**
1. **The Indus River System**
* Origin: **Tibet, near Lake Mansarovar**.
* Flows through Ladakh, Jammu & Kashmir, then into Pakistan, finally into the **Arabian Sea**.
* Main tributaries: **Zaskar, Nubra, Shyok, Hunza** (in Kashmir); further down: **Satluj, Beas, Ravi, Chenab, Jhelum**.
* Total length: **2,900 km**.
* Only **20% of its basin lies in India** (J\&K, Himachal Pradesh, Punjab, Haryana, Rajasthan).
2. **The Ganga River System**
* Origin: **Gangotri Glacier (Bhagirathi)** in Uttarakhand.
* Joins with **Alaknanda at Devprayag** (then called Ganga).
* Tributaries: **Yamuna, Ghaghara, Gandak, Kosi, Son, Chambal, Betwa, Ken**.
* Creates the **world's largest delta – Sundarbans Delta**, before entering the Bay of Bengal.
* Length in India: **2,500 km**.
3. **The Brahmaputra River System**
* Origin: **Tibet (near Mansarovar)**, known as **Tsangpo** there.
* Very long course; carries less silt in Tibet (dry region).
* Enters India in **Arunachal Pradesh** (called *Dihang*), then joins with **Dibang, Lohit, etc.**
* Known for its **huge volume of water** and frequent floods in Assam.
* Forms a vast delta with the Ganga before entering the Bay of Bengal.
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#### 4. The Peninsular Rivers
* Mostly **seasonal rivers**, dependent on monsoon rains.
* Shorter, shallower, and make small deltas/estuaries.
* **Major rivers:**
1. **Narmada River** – Rises from Amarkantak hills (Madhya Pradesh); flows west into the Arabian Sea; forms the **Marble Rocks at Jabalpur** and **Narmada Estuary**.
2. **Tapi River** – Originates from Satpura ranges (Madhya Pradesh); flows through Maharashtra and Gujarat into the Arabian Sea.
3. **Godavari River** – Longest Peninsular river (1,500 km), rises in Maharashtra, flows through Telangana, Andhra Pradesh; forms a large delta.
4. **Mahanadi River** – Rises in Chhattisgarh, flows into Odisha, forms fertile delta before entering Bay of Bengal.
5. **Krishna River** – Originates near Mahabaleshwar (Maharashtra); tributaries: Bhima, Tungabhadra; drains into Bay of Bengal.
6. **Kaveri River** – Originates in Karnataka; flows through Tamil Nadu into Bay of Bengal; forms fertile delta known as "granary of South India".
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#### 5. Lakes of India
* **Permanent lakes:** e.g., Wular Lake (J\&K).
* **Saltwater lakes:** e.g., Sambhar Lake (Rajasthan), Chilika Lake (Odisha).
* **Freshwater lakes:** e.g., Bhimtal, Nainital, Loktak.
* Formed by glaciers, tectonic activity, rivers, or human activities (dams, reservoirs).
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#### 6. Role of Rivers in Economy
* Provide **irrigation, drinking water, navigation, hydropower, fisheries**.
* River valleys are **densely populated** due to fertile soil and water supply.
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#### 7. River Pollution
* Rivers are polluted by **industrial waste, urban sewage, agricultural chemicals**.
* This reduces water quality and damages ecosystems.
* **Government programmes:**
* **Namami Gange Programme** (for Ganga).
* **National River Conservation Plan (NRCP)** for cleaning and protecting rivers.
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✅ **In short:**
India's drainage system is divided into **Himalayan (perennial, large deltas, fertile plains)** and **Peninsular rivers (seasonal, shorter, estuaries/deltas)**. Rivers and lakes are crucial for India's economy but are facing **pollution challenges**, which need conservation efforts.
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