Drainage (India Basic)

Drainage Systems In India

The drainage system of a country refers to the network of rivers and streams that drain a particular area. India, with its diverse topography, possesses a rich and varied drainage system. This system is primarily influenced by the relief features of the subcontinent. Indian rivers are broadly classified into two major groups based on their origin:

1. The Himalayan Rivers

2. The Peninsular Rivers

In addition to these major river systems, there are also smaller rivers flowing along the coasts and inland drainage systems in arid regions.

The Himalayan Rivers

The rivers originating from the Himalayan mountain ranges are perennial, meaning they flow throughout the year. This constant flow is sustained by both the melting snow from the high mountains during summer and the monsoon rainfall during the monsoon season. These rivers are young, youthful, and have long courses, often carving out deep gorges in their mountainous terrain. They also have the potential to cause significant erosion and depositional activities.

The major Himalayan river systems are:

The Indus River System

The Indus river, one of the longest rivers in Asia, originates from the Angsi Glacier in the Himalayas, near Mansarovar Lake in the Tibetan Plateau. It flows westwards through Ladakh, then enters Pakistan and flows through the plains before finally draining into the Arabian Sea.

Origin: Angsi Glacier, Himalayas (Tibet)

Course: Flows west through Ladakh, then south through Pakistan.

Tributaries: The Indus river has a large number of tributaries, the most significant of which join it in the Punjab plains. These include the Jhelum, Chenab, Ravi, Beas, and Sutlej. The Jhelum, Chenab, and Ravi originate in the Himalayas, while the Beas and Sutlej also have their sources in the Himalayas.

Confluence: The Sutlej, Ravi, Beas, Chenab, and Jhelum rivers all merge to form the Panjnad, which then joins the Indus.

Mouth: Arabian Sea.

Significance: The Indus basin is a fertile agricultural region. The Indus Water Treaty (1960) between India and Pakistan governs the use of its waters.

The Ganga River System

The Ganga is the most important river system in India, considered sacred by millions. It originates from the Gangotri Glacier in Uttarakhand. The river is formed after the Bhagirathi and Alaknanda meet at Devprayag.

Origin: Gangotri Glacier, Uttarakhand (Bhagirathi)

Course: Flows south and east through the Indo-Gangetic Plain.

Major Tributaries:

• Right Bank Tributaries: Yamuna (originating from Yamunotri Glacier, the longest and most important tributary, joins Ganga at Prayagraj), Son (originating from Amarkantak Plateau).
• Left Bank Tributaries: Ghaghara, Gandak, Kosi (known for its shifting course and floods in Bihar).

Confluence: The Ganga flows through India and then enters Bangladesh, where it is known as the Padma. It merges with the Brahmaputra (known as Jamuna in Bangladesh) to form the Meghna river, which ultimately drains into the Bay of Bengal.

Mouth: Bay of Bengal (forming the world's largest delta, the Sundarbans, along with the Brahmaputra).

Significance: The Ganga basin is densely populated and highly fertile, supporting a large agricultural economy. It is also a vital cultural and spiritual artery for India.

The Brahmaputra River System

The Brahmaputra river originates in the Chemayungdung Glacier in the Himalayas, close to Mount Kailash in Tibet. It flows eastwards through Tibet, then takes a southward bend in Arunachal Pradesh and flows into Assam.

Origin: Chemayungdung Glacier, Himalayas (Tibet)

Course: Flows east through Tibet (as Yarlung Tsangpo), then south through Arunachal Pradesh and Assam in India, and finally enters Bangladesh.

Tributaries: In India, its major tributaries include Dibang, Lohit, Siang, Dhansiri, and Manas.

Confluence: In Bangladesh, it is known as the Jamuna and merges with the Padma (Ganga) to form the Meghna.

Mouth: Bay of Bengal.

Significance: The Brahmaputra is a powerful river known for its braided channels and its tendency to cause extensive flooding and erosion in Assam. It carries a large volume of water and silt.

The Peninsular Rivers

The rivers of peninsular India are largely seasonal, their water flow depending on the monsoon rainfall. They originate from the Western Ghats and flow eastwards towards the Bay of Bengal, except for a few that flow westwards into the Arabian Sea. These rivers are older than the Himalayan rivers and have carved broad, shallow valleys.

The Narmada Basin

Origin: Amarkantak Plateau in Madhya Pradesh.

Course: Flows westwards through a rift valley formed between the Vindhya Range (north) and the Satpura Range (south). It creates beautiful rocky gorges and waterfalls, such as the Dhuan Dhar Falls near Jabalpur.

Mouth: Arabian Sea, near Bharuch in Gujarat.

Significance: It is one of the few major peninsular rivers that flow westwards. Its basin is an important region for minerals.

The Tapi Basin

Origin: Satpura range in Madhya Pradesh.

Course: Flows westwards, parallel to the Narmada, also through a rift valley, between the Satpura and Ajanta ranges.

Mouth: Arabian Sea, near Surat in Gujarat.

Significance: It is the second-largest west-flowing river of the peninsula.

The Godavari Basin

Origin: Trimbak Plateau in the Western Ghats in Maharashtra.

Course: Flows eastwards across the Deccan Plateau, passing through Maharashtra, Telangana, and Andhra Pradesh.

Tributaries: A large number of tributaries, including Penganga, Wainganga, Wardha, Indravati, Pranhita, and Manjra. The confluence of Penganga, Wainganga, and Wardha forms the Pranhita.

Mouth: Bay of Bengal, forming a delta.

Significance: It is the longest peninsular river and is often referred to as the 'Dakshin Ganga' (Ganga of the South) due to its length and religious importance.

The Mahanadi Basin

Origin: Highlands of Chhattisgarh.

Course: Flows eastwards through Odisha.

Mouth: Bay of Bengal, forming a delta.

Significance: The Hirakud Dam on the Mahanadi is one of the longest dams in India and is crucial for irrigation and power generation.

The Krishna Basin

Origin: Mahabaleshwar in the Western Ghats, Maharashtra.

Course: Flows eastwards across the Deccan Plateau, passing through Maharashtra, Karnataka, and Andhra Pradesh.

Tributaries: Bhima, Tungabhadra, Koyna, Musi, and Ghataprabha.

Mouth: Bay of Bengal, forming a delta.

Significance: Its basin is agriculturally important, especially for rice cultivation.

The Kaveri Basin

Origin: Brahmagiri range of the Western Ghats in Karnataka.

Course: Flows southwards through Karnataka and Tamil Nadu. It splits into several channels, creating a large delta in its lower course.

Tributaries: Harangi, Hemavati, Amravati, Bhavani, and Kabini.

Mouth: Bay of Bengal.

Significance: The Kaveri basin is a highly fertile region and is crucial for irrigation and hydroelectricity production, particularly in Tamil Nadu.

Lakes

India is blessed with a large number of natural and man-made lakes, which vary greatly in size, character, and origin. These lakes play a significant role in the environment and economy.

Classification of Lakes based on Origin:

1. Ox-bow Lakes: Formed by the meandering process of rivers. The cut-off portion of the river bend forms a crescent-shaped lake. For example, Wular Lake in Jammu and Kashmir, though primarily glacial, also has ox-bow lake characteristics in its lower reaches.
2. Glacial Lakes: Formed by the action of glaciers, often in the Himalayas. These lakes are typically large and deep. Examples include Pangong Tso and Tso Moriri in Ladakh.
3. Tectonic Lakes: Formed due to crustal movements, depressions, or faulting. Dal Lake and Nainital Lake in Uttarakhand are examples of tectonic lakes.
4. Lagoon Lakes: Coastal bodies of water separated from the sea by a barrier of sand or coral. Chilika Lake in Odisha and Vembanad Lake in Kerala are examples of brackish water lagoons.
5. Man-made Lakes: Formed by the construction of dams and reservoirs for irrigation, hydropower, and water supply. Examples include Govind Ballabh Pant Sagar (Rihand Dam) and Bhakra Nangal reservoir.
6. Saltwater Lakes: Formed in arid regions due to evaporation exceeding precipitation, leading to high salinity. Sambhar Lake in Rajasthan is the largest inland salt lake in India.

Importance of Lakes:

• Water Storage: They act as reservoirs for irrigation, drinking water, and industrial use.
• Hydel Power: Many lakes are associated with dams that generate hydroelectricity.
• Flood Control: Lakes can help regulate river flow and mitigate floods.
• Tourism and Recreation: They are significant attractions for tourism, supporting activities like boating, fishing, and leisure.
• Aquatic Biodiversity: Lakes provide habitats for a wide range of flora and fauna, contributing to biodiversity.
• Climate Moderation: Large water bodies can have a moderating effect on local climate.

Role Of Rivers In The Economy

Rivers are fundamental to the Indian economy, deeply intertwined with its development and the livelihoods of its people. Their multifaceted roles are:

1. Agriculture: This is the most significant contribution. Rivers provide water for irrigation through canals and reservoirs, enabling cultivation in vast areas, especially in the Indo-Gangetic plains. This ensures food security for the nation.

2. Hydroelectric Power: Dams built across rivers generate vast amounts of hydroelectricity, a clean and renewable energy source vital for industrial and domestic consumption across the country.

3. Inland Navigation: Several rivers, particularly in eastern India (like the Ganga, Brahmaputra, and their tributaries), are navigable and serve as important national waterways for the cost-effective transport of goods and passengers.

4. Water Supply: Rivers are the primary source of water for drinking, sanitation, and various industrial processes. Cities and industries are often located along riverbanks due to this dependency.

5. Fishing: Rivers support a significant fishery industry, providing a source of livelihood and protein for millions of people, especially in rural and coastal areas.

6. Tourism and Recreation: The scenic beauty of river valleys, waterfalls, and riverfronts attracts tourists. Activities like river rafting, boating, and religious tourism contribute to local economies.

7. Groundwater Recharge: The presence of rivers and their floodplains aids in recharging groundwater aquifers, which is essential for maintaining water tables and supporting wells and borewells.

8. Industrial Cooling: Water from rivers is extensively used by industries for cooling purposes.

9. Fertility and Alluvial Deposits: The silt deposited by rivers during floods makes the surrounding land highly fertile, ideal for agriculture.

River Pollution

River pollution is a critical environmental issue in India, threatening both ecosystems and public health. A significant number of India's rivers are heavily polluted due to a combination of factors:

Major Sources of Pollution:

1. Untreated Domestic Sewage: This is arguably the largest contributor. A vast amount of sewage generated from urban and rural households is discharged directly into rivers without adequate treatment. This introduces organic waste, pathogens (bacteria, viruses), nutrients (nitrogen, phosphorus), and suspended solids.

2. Industrial Effluents: Industries, particularly chemical, textile, paper, and leather tanneries, release a wide array of toxic chemicals, heavy metals (like mercury, lead, chromium), acids, alkalis, and high temperatures into rivers. These pollutants are often far more damaging than sewage.

3. Agricultural Runoff: Fertilizers (containing nitrates and phosphates) and pesticides/herbicides used in farming are washed off from fields into rivers during rain or irrigation. This leads to eutrophication (excessive nutrient enrichment), causing algal blooms that deplete dissolved oxygen, harming aquatic life.

4. Religious and Cultural Practices: The immersion of idols, ashes, flowers, and other religious offerings during festivals directly adds pollutants like plastics, metals, and organic matter to rivers.

5. Solid Waste Disposal: Unmanaged dumping of municipal solid waste, including plastics, directly into rivers or on their banks contaminates the water and blocks natural flow.

6. Thermal Pollution: Discharge of hot water from thermal power plants and industries can raise the river's temperature, reducing dissolved oxygen and affecting aquatic species.

Consequences of River Pollution:

• Health Impacts: Contaminated water is a major cause of waterborne diseases such as cholera, typhoid, dysentery, hepatitis, and skin infections.
• Ecological Damage: Pollutants kill fish and other aquatic organisms, disrupt food chains, and damage aquatic habitats. Eutrophication leads to 'dead zones' with little or no oxygen.
• Impact on Livelihoods: Pollution affects fishing communities, the availability of clean water for agriculture, and tourism.
• Economic Costs: Significant expenses are incurred in treating polluted water for drinking and in managing the health consequences of pollution.

Government Initiatives:

To address this crisis, the Indian government has launched several programs like the National River Conservation Plan (NRCP) and the more ambitious Namami Gange Programme, which aims at the holistic rejuvenation of the Ganga river basin through sewage treatment, industrial pollution control, afforestation, and public participation.