Chapter 3: Drainage

This chapter explores India’s drainage systems, where rivers and their tributaries form networks that drain into seas, lakes, or oceans. It covers the concept of drainage basins, water divides, Himalayan and Peninsular rivers, lakes, the economic role of rivers, and challenges like river pollution.

1. Drainage Basics

Drainage: The river system of an area, where small streams join to form a main river that drains into a large water body (e.g., sea, lake).

Drainage Basin: The area drained by a single river system. The Amazon has the world’s largest drainage basin.

Water Divide: An elevated area (e.g., mountain, upland) separating two drainage basins. Example: Ambala divides the Indus and Ganga systems.

Largest Basin in India: The Ganga river has the largest drainage basin in India.

2. Drainage Systems in India

Classification: Indian rivers are divided into two groups based on relief features:

Himalayan Rivers: Perennial, long courses, originate in mountains.
Peninsular Rivers: Mostly seasonal, shorter courses, originate in plateaus or hills.

Comparison of Himalayan and Peninsular Rivers:

Feature	Himalayan Rivers	Peninsular Rivers
Flow	Perennial (rain + snowmelt)	Seasonal (rain-dependent)
Course	Long, with gorges, meanders, deltas	Short, shallow, some form estuaries
Erosion	Intensive in upper courses, carry silt	Less erosional, smaller sediment load
Examples	Indus, Ganga, Brahmaputra	Godavari, Narmada, Tapi

3. Himalayan Rivers

Overview: Long, perennial rivers with large tributaries, forming river systems. Major rivers: Indus, Ganga, Brahmaputra.

Indus River System:

Source: Near Lake Mansarovar, Tibet; enters India in Ladakh, flows west.
Tributaries: Zaskar, Nubra, Shyok, Hunza (Kashmir); Satluj, Beas, Ravi, Chenab, Jhelum (join near Mithankot, Pakistan).
Course: 2,900 km, drains into Arabian Sea east of Karachi. Gentle slope in Indus plain.
Basin: One-third in India (Ladakh, Jammu and Kashmir, Himachal Pradesh, Punjab); rest in Pakistan.
Indus Water Treaty (1960): India uses 20% of water for irrigation in Punjab, Haryana, Rajasthan.

Ganga River System:

Source: Bhagirathi (Gangotri Glacier) joins Alaknanda at Devaprayag, Uttarakhand, to form Ganga.
Tributaries: Himalayan (Yamuna from Yamunotri, Ghaghara, Gandak, Kosi from Nepal Himalaya); Peninsular (Chambal, Betwa, Son from uplands).
Course: Over 2,500 km, emerges at Haridwar, flows east to Farakka (West Bengal), bifurcates into Bhagirathi-Hooghly (Bay of Bengal) and mainstream (joins Brahmaputra in Bangladesh as Meghna).
Delta: Sundarban Delta, world’s largest and fastest-growing, named after Sundari trees, home to Royal Bengal tigers.
Features: Gentle slope (1 m per 6 km), large meanders, floods enrich soil but cause damage.
Namami Gange (2014): Conservation mission to reduce pollution and rejuvenate Ganga (http://nmcg.nic.in).

Brahmaputra River System:

Source: East of Mansarovar, Tibet (Tsang Po), near Indus and Satluj sources.
Course: Slightly longer than Indus, flows east parallel to Himalayas, turns at Namcha Barwa (7,757 m), enters India as Dihang in Arunachal Pradesh, becomes Brahmaputra in Assam, and Jamuna in Bangladesh.
Tributaries: Dibang, Lohit, others in Assam.
Features: Braided channels, forms riverine islands (e.g., Majuli, world’s largest), carries heavy silt in India due to high rainfall, frequent floods in Assam and Bangladesh, shifting channels.

4. Peninsular Rivers

Overview: Mostly seasonal, shorter courses, smaller basins. Western Ghats form the main water divide. East-flowing rivers (e.g., Godavari, Krishna) form deltas; west-flowing rivers (e.g., Narmada, Tapi) form estuaries.

Narmada Basin:

Source: Amarkantak hills, Madhya Pradesh; flows west in a rift valley.
Features: Creates Marble Rocks (Jabalpur), Dhuadhar Falls; short tributaries join at right angles.
Basin: Madhya Pradesh, Gujarat.
Namami Devi Narmade: Madhya Pradesh’s conservation mission (http://www.namamidevinarmade.mp.gov.in).

Tapi Basin:

Source: Satpura ranges, Betul, Madhya Pradesh; flows west in a rift valley, shorter than Narmada.
Basin: Madhya Pradesh, Gujarat, Maharashtra.

Godavari Basin:

Source: Western Ghats, Nasik, Maharashtra; flows 1,500 km to Bay of Bengal.
Features: Largest Peninsular river, called Dakshin Ganga, largest basin among Peninsular rivers.
Tributaries: Purna, Wardha, Pranhita, Manjra, Wainganga, Penganga.
Basin: Maharashtra (50%), Madhya Pradesh, Odisha, Andhra Pradesh.

Mahanadi Basin:

Source: Chhattisgarh highlands; flows 860 km to Bay of Bengal.
Basin: Maharashtra, Chhattisgarh, Jharkhand, Odisha.

Krishna Basin:

Source: Near Mahabaleshwar, Maharashtra; flows 1,400 km to Bay of Bengal.
Tributaries: Tungabhadra, Koyana, Ghatprabha, Musi, Bhima.
Basin: Maharashtra, Karnataka, Andhra Pradesh.

Kaveri Basin:

Source: Brahmagiri range, Western Ghats; flows 760 km to Bay of Bengal, south of Cuddalore, Tamil Nadu.
Tributaries: Amravati, Bhavani, Hemavati, Kabini.
Basin: Karnataka, Kerala, Tamil Nadu.
Feature: Shivasamudram Falls, second largest waterfall in India, generates hydroelectric power for Mysuru, Bengaluru, Kolar Gold Field.

Other East-Flowing Rivers: Damodar, Brahmani, Baitarni, Subarnrekha.

West-Flowing Coastal Rivers: Short, include Sabarmati, Mahi, Bharathpuzha, Periyar (drain into Arabian Sea; states: Gujarat, Kerala).

Largest Waterfall in India: Jog Falls (Sharavathi River, Karnataka).

5. Lakes

Types:

Natural: Formed by glaciers (e.g., Wular, Dal, Nainital, Bhimtal, Loktak, Barapani), river action (ox-bow lakes), coastal spits/bars (Chilika, Pulicat, Kolleru), or inland drainage (Sambhar, a saltwater lake in Rajasthan for salt production).
Artificial: Formed by damming rivers for hydropower (e.g., Gobind Sagar, Rana Pratap Sagar, Nizam Sagar, Nagarjuna Sagar, Hirakud).

Key Lakes:

Wular: Largest freshwater lake in India, Jammu and Kashmir, tectonic origin.
Chilika: Largest saltwater lake, Odisha, coastal lagoon.

Significance: Regulate river flow, prevent flooding, maintain water supply, support hydropower, moderate climate, sustain ecosystems, boost tourism (e.g., Dal Lake, Kashmir).

6. Role of Rivers in the Economy

Historical Importance: Rivers attracted ancient settlements, now major cities (e.g., Delhi on Yamuna, Kolkata on Hooghly).

Economic Benefits:

Irrigation: Essential for agriculture, India’s primary livelihood.
Navigation: Facilitates transport (e.g., Brahmaputra in Assam).
Hydropower: Dams generate electricity (e.g., Bhakra Nangal).
Settlement: Riverbanks support urban growth.

7. River Pollution

Causes: Domestic, municipal, industrial, and agricultural waste reduce water volume and quality, impairing rivers’ self-cleansing ability.

Impact: Polluted water affects health, ecosystems, and agriculture. Ganga can dilute pollution within 20 km, but urbanization overwhelms this capacity.

Conservation Efforts:

Ganga Action Plan (1985): Initiated river cleaning.
National River Conservation Plan (1995): Expanded to other rivers, aims to improve water quality via pollution abatement (http://nrcd.nic.in/nrcp.pd).

8. Summary Table

River/Lake	Key Features	Basin/Location
Indus	2,900 km, perennial, gorges, drains into Arabian Sea	Ladakh, J&K, HP, Punjab
Ganga	Over 2,500 km, Sundarban Delta, meanders	North India, Bangladesh
Brahmaputra	Braided, floods, Majuli island, drains into Bay of Bengal	Arunachal Pradesh, Assam
Godavari	1,500 km, largest Peninsular river, delta	Maharashtra, MP, Odisha, AP
Narmada	Rift valley, west-flowing, estuary	MP, Gujarat
Wular	Largest freshwater lake, tectonic	Jammu and Kashmir
Chilika	Largest saltwater lake, coastal lagoon	Odisha

9. Summary and Key Takeaways

Drainage Systems: Himalayan rivers (perennial, long) and Peninsular rivers (seasonal, short) shape India’s geography.

Economic Role: Rivers support agriculture, navigation, hydropower, and urban growth.

Lakes: Natural and artificial lakes enhance tourism, regulate water, and support ecosystems.

Pollution: Rising pollution threatens rivers, addressed by plans like Namami Gange and NRCP.