DRAINAGE

Small streams following different directions come together and form the Main River, which ultimately drains into large water bodies such as lakes, seas, and oceans. The area drained by a single river system is called a drainage basin. Rivers play an important role in human livelihood. World's largest drainage basin Nile River basin in Egypt.

India has a complex and extensive network of drainage systems, including rivers, lakes, and other water bodies. The drainage systems in India can be broadly categorized into two types: the Himalayan drainage system and the Peninsular drainage system.  Nearly 77 % of the river water drains into the Bay of Bengal and the remaining 23% drains into the Arabian Sea.

1. Rivers of Inland drainage system

Inland drainage systems in India refer to rivers that don't reach the ocean but end up in lakes, or inland seas, or simply disappear in deserts due to evaporation or infiltration. While not as numerous as their oceanic counterparts, these rivers play a vital role in the arid and semi-arid regions of India. 

Himalayan System

• Ghaggar River: Once a tributary of the Indus, it now flows through Punjab and Haryana before petering out in the Thar Desert near Hanumangarh. Its ancient course is considered to be the mythical Saraswati River.
• Luni River: Originates in the Aravalli Range near Ajmer and flows through Rajasthan, eventually disappearing in the Rann of Kutch. It's the longest river in the Thar Desert and supports various salt lakes and wildlife habitats.

Peninsular System

• Luni River (Separate from the Himalayan Luni): This Luni River originates in the Vindhya Range and flows through Madhya Pradesh and Gujarat, finally disappearing in the Little Rann of Kutch. It's known for its seasonal waterfalls and historical significance.
• Sukli River: Flows through Maharashtra and disappears in the saline marshes of the Thane Creek near Mumbai. It's crucial for the Thane Creek Flamingo Sanctuary and supports various coastal ecosystems.
• Machkund River: Forms the border between Odisha and Andhra Pradesh before emptying into the Chilka Lake, the largest brackish water lagoon in India. It's vital for the lake's ecology and supports fishing and tourism.

Other Notable Rivers

• Aksai Chin River: Flows through the Ladakh region and ends in the Aksai Chin desert, contributing to the wetland ecosystem there.
• Banaskantha River: A seasonal river in Rajasthan that disappears in the Thar Desert, playing a role in local water security and agriculture.

2. The Himalayan Rivers 

The Indus, the Ganga and the Brahmaputra are the major rivers in the Himalayas.

The Indus river system

• The River Indus rises in Tibet, near Lake Mansarovar. Flowing west, it enters India in Ladakh.
• The right-bank tributaries:  Shyok Kabul, Sangar, Gilgit, Khurram, Kunar, Hunza, Tochi, Nubra  Gomal
• The left-bank tributaries:  Zaskar ‘Panjnad’ the Sutlej, the Beas, the Ravi, and the Chenab.
• It flows through Baltistan and Gilgit and emerges from the mountains at Attock.
• The Sutlej, the Beas, the Ravi, the Chenab and the Mithantok are in Pakistan.
• It reaches the Arabian Sea, near the east of Karachi after flowing a total length of 2900 km.
• Indus Water Treaty (1960], India can use only 20 per cent of the total water carried by the Indus River system. This water is used for irrigation in Punjab, Haryana and the southern and western parts of Rajasthan.

The Ganga River System

• The Ganga called the ‘Bhagirathi’ is fed by the Gangotri Glacier and joined by the Alaknanda at Devaprayag in Uttarakhand. At Haridwar, the Ganga emerges from the mountains onto the plains.
• Right Bank Tributaries of the Ganga River: Yamuna, Chambal River, Banas River, Sind River, Betwa River, Ken River, Son River and Damodar River. 
• Left Bank Tributaries of the Ganga River: Ramganga River, Gomati River, Ghaghara River, Kali River, Gandak River, Burhi Gandak River and Kosi River.         
• The river Yamuna rises from the Yamunotri Glacier in the Himalayas. As right bank tributary meets the Ganga at Allahabad. The Ghaghara, the Gandak and the Kosi rise in Nepal and cause widespread floods every year.
• The Chambal the Son and the Betwa rise from semi-arid places causing less water with them.
• At Farakka in West, Bengal Ganga bifurcates into the Bhagirathi-Hooghly and the mainstream flows into Bangladesh and joins with the Brahmaputra River. The length of the Ganga is 2500 km.

The Brahmaputra river system

• It rises in Tibet east of Mansarovar Lake very close to the sources of the Indus and the Satluj.
• Namcha Barwa (7757 m), takes a ‘U-turn and enters India in Arunachal Pradesh.
• It is known as Tsang Po in Tibet and Jamuna In Bangladesh.
• It causes widespread floods in Assam and Bangladesh during the rainy season.
• Left bank tributaries: Burhi Dihing, Dhansari ,Kalang.
• Right bank tributaries: Subansiri, Kameng, Manas, Sankosh.

3. The Peninsular Rivers

It is the oldest river system in India. The major rivers of the Peninsula, such as the Mahanadi, the Godavari, the Krishna and the Kaveri flow eastwards and drain into the Bay of Bengal. The Narmada and the Tapi are the only long rivers, which flow west and drain into the Arabian Sea.

The Narmada basin: It rises in Amarkantak Hills Madhya Pradesh the Malabar rocks near Jabalpur and the Dhuadhar Falls are notable ones. The Narmada River conservation mission has been undertaken by the government of Madhya Pradesh through a scheme named Namami Devi Narmada. It covers parts of Madhya Pradesh and Gujarat.

The Tapi basin: The Tapi rises in the Satpura ranges in Madhya Pradesh and also flows through the Rift Valley. It flows through Madhya Pradesh, Gujarat and Maharashtra. The main west-flowing rivers are Sabarmati, Mahi, Bharathpuzha and Periyar.

The Godavari basin

• It is the largest Peninsular River, it rises from Nasik. It has a total length of about 1500 km.
• Its drainage basin comprises parts of Maharashtra, Madhya Pradesh, Orissa, Andhra Pradesh and Telangana.
• Tributaries: The Purna, the Wardha, the Penganga, and the Wainganga.
• It is also known as Dakshin Ganga.

The Mahanadi basin: It rises in Chhattisgarh and flows in Orissa to reach the Bay of Bengal. it has a total length of 860 km.

The Krishna Basin: Rising from Mahabaleshwar flows 1400 km through Maharashtra, Karnataka, Telangana and Andhra Pradesh. Tributaries: The Tungabhadra, the Konya, the Ghatprabha, the Musi and the Bhima.

The Kaveri basin: It rises the Brahma Giri range in the western ghats and reaches the Bay of Bengal through Karnataka, Kerala, and Tamil Nadu with a length of 760 km. Tributaries: - Amravati, Bhavani, Hemavati, and Kabini.

Other small rivers flow towards the east.

• The Damodar River: It flows across the Jharkhand and West Bengal. Tributaries: Barakar, Konar, Bokaro, Haharo, Jamunia, Ghari, Guaia, Khadia and Bhera.
• The Brahmani River: The Brahmani is formed by the confluence of the Sankh and South Koel rivers. It is the second widest river in Odisha after Mahanadi. 
• Subarnarekha River: The Subarnarekha River flows through the Indian states of Jharkhand, West Bengal, and Odisha. The name "Subarnarekha" translates to "Streak of Gold," and the river is known for its golden-hued sands. It is an important river in terms of agriculture and supports local communities along its course.
• Vamsadhara River: The Vamsadhara River, also known as the Bansadhara, flows through the Indian states of Odisha and Andhra Pradesh. The river is a crucial water source for agriculture in the region it traverses. It originates in the Eastern Ghats and eventually flows into the Bay of Bengal.
• Pennar River: The Pennar River flows through the southern Indian states of Karnataka and Andhra Pradesh. The Pennar is known for its important role in providing water for agriculture. It has several tributaries and contributes to the irrigation of a significant portion of the region.
• Palar River: The Palar River flows through the southern Indian states of Karnataka and Tamil Nadu. The Palar is significant for its historical and cultural importance. It has been mentioned in ancient Indian literature, and its waters have been harnessed for irrigation. However, like many rivers in the region, it faces challenges such as water scarcity and pollution.
• Vaigai River: The Vaigai River flows through the Indian state of Tamil Nadu. The Vaigai is an important river in the region, supporting agriculture and providing water for irrigation. The river is also associated with cultural and historical significance, with several ancient temples and settlements along its banks.

Other small rivers flowing towards the west

• Gujarat: The Shetruniji, The Bhadra, The Dhadhar, Sabarmati and Mahi.
• Maharashtra: The Vatharini,  the Kalinada and Bedti.
• The Saraswati River in Karnataka, Jog or Gersoppa Falls (289m) highest waterfall in India.
• Goa: Mandovi Jauri.
• Kerala: Bharathapuzha, The Periyar and The Pamba River.

The difference between the Himalayas and the peninsular rivers

River pollution: River pollution refers to the contamination of rivers with harmful substances, which can have detrimental effects on water quality, aquatic ecosystems, and human health. The sources of river pollution are diverse, ranging from industrial discharges and agricultural runoff to improper waste disposal and urban activities.

4. Lakes

Lakes are large bodies of water that are generally surrounded by land. They can vary greatly in size, depth, and characteristics, and they are found on every continent.

Lakes can form through various processes, including tectonic activity, glacial activity, volcanic activity, and human activities such as dam construction. Tectonic activity can create lakes through the shifting of the Earth's crust, leading to the formation of basins. Glacial activity, such as the melting of glaciers, can carve out depressions that fill with water.

Types of Lakes

Lakes support a variety of ecosystems, including aquatic plants, fish, and other wildlife. The health of a lake ecosystem is influenced by factors such as water temperature, nutrient levels, and the presence of pollutants.

Nutrient Levels: Lakes can be categorized based on their nutrient levels:

• Oligotrophic Lakes: Low in nutrients, clear water, and often deep.
• Mesotrophic Lakes: Moderate in nutrients and productivity.
• Eutrophic Lakes: High in nutrients, supporting abundant plant and algae growth. This can lead to issues such as algal blooms.

Uses

Top Ten largest lakes in India.