1. Introduction

Drainage: River system of an area.

• Drainage Basin: Area drained by a single river system.
• Water Divide: Elevated area (upland/mountain) separating two drainage basins. (e.g., Ambala separates Indus & Ganga).

2. Himalayan Rivers (हिमालयी नदियाँ)

Most are Perennial (have water throughout year from rain + snow).

A. Indus River System:

• Source: Tibet (near Lake Mansarowar).
• Enters India in Ladakh.
• Tributaries: Zaskar, Nubra, Shyok, Hunza (Kashmir).
• Satluj, Beas, Ravi, Chenab, Jhelum join near Mithankot (Pak).
• Total Length: 2900 km. (One of longest in world).
• Indus Water Treaty (1960): India can use only 20% of water.

B. Ganga River System:

• Headwaters: Bhagirathi (fed by Gangotri Glacier).
• Joins Alaknanda at Devaprayag → Called Ganga.
• Emerges on plains at Haridwar.
• Length: Over 2500 km.
• Major Tributaries: Yamuna (Allahabad), Ghaghara, Gandak, Kosi.
• Flows to Farakka (WB) → Bifurcates → Bhagirathi-Hooghly (South) & Mainstream (Bangladesh) → Joined by Brahmaputra → Meghna → Bay of Bengal.
• Forms Sundarban Delta (Largest/Fastest growing).

Mostly Seasonal (dependent on rainfall). Shorter & shallower courses.

West Flowing Rivers (Make Estuaries)

• Narmada: Rises in Amarkantak (MP). Flows in Rift Valley.
  → Creates ‘Marble Rocks’ (Jabalpur) & ‘Dhuadhar Falls’.
• Tapi: Rises in Satpura ranges (Betul, MP). Flows parallel to Narmada but shorter.
• Other West Flowing: Sabarmati, Mahi, Bharathpuzha, Periyar.

East Flowing Rivers (Make Deltas)

1. Godavari (“Dakshin Ganga”):

• Largest Peninsular river (1500 km).
• Source: Nasik (Maharashtra).
• Tributaries: Purna, Wardha, Pranhita, Manjra, Wainganga, Penganga.
• Basin covers: Maharashtra (50%), MP, Odisha, AP.

2. Mahanadi:

• Source: Highlands of Chhattisgarh.
• Length: 860 km. Flows through Odisha to Bay of Bengal.

3. Krishna:

• Source: Spring near Mahabaleshwar.
• Length: 1400 km.
• Tributaries: Tungabhadra, Koyana, Ghatprabha, Musi, Bhima.

4. Kaveri:

• Source: Brahmagiri range (Western Ghats).
• Length: 760 km.
• Falls: Shivasamudram (2nd biggest in India) -> Hydroelectricity for Mysore/Bangalore.

3. Lakes (झीलें)

• Wular Lake (J&K): Largest freshwater lake in India. (Tectonic activity).
• Dal Lake, Bhimtal, Nainital, Loktak, Barapani: Freshwater lakes.
• Chilika, Pulicat, Kolleru: Lagoons (Coastal areas).
• Sambhar Lake (Rajasthan): Salt water lake (Used for producing salt).
• Guru Gobind Sagar: Artificial lake (Bhakra Nangal Project).

Importance of Lakes:

• Regulate river flow (prevent floods/maintain flow in dry season).
• Hydel power generation.
• Moderate climate & aquatic ecosystem.
• Tourism & Recreation.

4. Role of Rivers in Economy

• Basic natural resource essential for human activities.
• Settlements on banks became big cities.
• Used for: Irrigation, Navigation, Hydro-power generation.
• Crucial for agriculture (India’s major livelihood).

5. River Pollution

• Causes: Heavy load of untreated sewage & industrial effluents.
• Growing domestic, municipal, industrial demand reduces water volume.
• Affects self-cleansing capacity (e.g., Ganga needs flow to dilute pollution).