Drainage of a river refers to the network of natural or artificial channels through which water flows from higher elevations to lower elevations, eventually reaching a common outlet, such as a lake, sea, or ocean. It is a crucial component of the water cycle, as it allows excess water from precipitation and runoff to be efficiently transported and discharged, preventing flooding and maintaining the flow of water in the landscape.
There are several types of drainage patterns that can be observed in river systems, and these patterns are determined by the underlying geological and topographical characteristics of the area. The primary types of drainage patterns include:
- Dendritic Drainage Pattern: The dendritic pattern is the most common and widespread type of drainage pattern, often resembling the branching structure of tree roots. In this pattern, the main river channel is joined by numerous smaller tributaries, creating a network of interconnected streams. It is commonly found in areas with uniform geology, where the underlying rock is relatively flat and consistent. E.g. The rivers of the northern plains; Indus, Ganga and Brahmaputra.
- Trellis Drainage Pattern: The trellis pattern is characterized by parallel main rivers with short tributaries flowing into them at right angles. This pattern typically occurs in regions with folded or tilted rock layers, where alternating bands of hard and soft rock create a landscape with parallel valleys and ridges. E.g. The rivers in the upper part of the Himalayan region; Indus, Ganga, and Brahmaputra.
- Rectangular Drainage Pattern: The rectangular pattern forms when rivers follow the pattern of intersecting joint or fault systems in the underlying rock. The streams tend to flow along the straight lines of these geological features, creating a grid-like pattern. E.g. Streams found in the Vindhya mountain range; Chambal, Betwa, and Ken.
- Radial Drainage Pattern: The radial pattern is observed when rivers flow outward in various directions from a central high point, such as a volcano or a dome-shaped mountain. This pattern is commonly found in volcanic regions. E.g. The rivers originating from the Amarkantak range; Narmada and Son (a tributary of Ganga).
- Annular Drainage Pattern: The annular pattern consists of rivers flowing around the edges of a circular or slightly elongated highland region, resembling a ring-like shape. This pattern is often associated with structural domes or basins.
- Deranged Drainage Pattern: The deranged pattern is a random and irregular drainage network with no clear geometric pattern. It typically occurs in regions that have undergone recent glaciations, where the landscape was heavily modified by glacial erosion, leaving behind a chaotic drainage system.
- Centripetal drainage pattern: A centripetal drainage pattern is a type of river network where rivers or streams flow inward and converge towards a central point. This pattern is characterized by numerous smaller watercourses merging into larger rivers at the center of a basin or depression. It is essentially the opposite of a radial drainage pattern, where rivers flow outward from a central point. E.g. Loktak lake in Manipur.
- Parallel Drainage Pattern: In a parallel pattern, multiple streams flow roughly parallel to each other. This pattern often develops in regions with steep slopes and easily erodible rock, where numerous small streams flow down the terrain without converging. E.g. The rivers of the northern plains; Indus, Ganga, and Brahmaputra.
Drainage systems in India
Himalayan River System
The Himalayan river system is one of the most extensive and significant river systems in the world. It comprises several major rivers originating from the Himalayan mountain range, which spans across several countries, including India, Nepal, Bhutan, China (Tibet), and Pakistan. Three of the most prominent rivers in this system are the Indus, Ganga (also known as the Ganges), and Brahmaputra. Let’s explore each river system in detail:
- Indus River System: The Indus River is one of the longest rivers in Asia, originating from the Tibetan Plateau in China. It then flows through India and Pakistan before emptying into the Arabian Sea. The Indus River system is crucial for the economy and agriculture of Pakistan, and it played a significant historical role in the development of ancient civilizations like the Indus Valley Civilization.
Key Tributaries:
- Jhelum River: It is one of the major tributaries of the Indus and flows through the Kashmir Valley in India before entering Pakistan.
- Chenab River: Originating from the glaciers of Himachal Pradesh in India, the Chenab is the largest tributary of the Indus.
- Ravi River: The Ravi also originates in India, near the Rohtang Pass in Himachal Pradesh, and flows through the state of Punjab before entering Pakistan.
- Ganga River System: The Ganga River is one of the most sacred and revered rivers in India, originating from the Gangotri Glacier in Uttarakhand, in the western Himalayas. It is considered the lifeline of the northern Indian plains and supports millions of people through its extensive basin.
Key Tributaries:
- Yamuna River: The Yamuna, originating from the Yamunotri Glacier in Uttarakhand, is the largest tributary of the Ganga and flows through states like Uttar Pradesh and Delhi.
- Son River: The Son River is an important southern tributary of the Ganga, originating from Amarkantak in Madhya Pradesh.
- Gandak River: The Gandak, also known as the Narayani River, flows through Nepal and Bihar before joining the Ganga.
- Brahmaputra River System: The Brahmaputra River is one of the major rivers in South Asia, with its origin in Tibet (China) as the Yarlung Tsangpo River. It enters India through Arunachal Pradesh and later flows through Assam, where it is called the Brahmaputra. The river further enters Bangladesh and finally joins the Ganga delta to form the world’s largest river delta, known as the Sunderbans, before emptying into the Bay of Bengal.
Key Tributaries:
- Subansiri River: The Subansiri is the largest tributary of the Brahmaputra, originating in Tibet and flowing through Arunachal Pradesh.
- Manas River: Originating in Bhutan, the Manas River flows through Assam before joining the Brahmaputra.
The Himalayan river system plays a crucial role in supporting the ecosystem, biodiversity, agriculture, and the livelihoods of millions of people across the Indian subcontinent. However, these rivers also face various challenges, including pollution, over-extraction of water, and the impacts of climate change, which call for sustainable management and conservation efforts.
Peninsular Drainage System
The Peninsular drainage system in India refers to the network of rivers that flow mainly in the peninsular region of the country, which comprises the Deccan Plateau and the surrounding areas. Unlike the Himalayan river system, the Peninsular rivers are generally shorter in length and have a more seasonal flow due to the varying rainfall patterns in the region. The rivers in this system are older and have a greater tendency to flow towards the east or southeast direction.
Major Rivers of the Peninsular Drainage System in India:
- Godavari River: The Godavari is the second-longest river in India, originating from the slopes of the Western Ghats in Maharashtra. It flows eastwards through several states, including Maharashtra, Telangana, Andhra Pradesh, and finally empties into the Bay of Bengal. The Godavari basin is agriculturally rich and supports the livelihoods of millions of people.
- Krishna River: The Krishna River also originates from the Western Ghats but flows southwards through the states of Maharashtra, Karnataka, and Andhra Pradesh. It has several major tributaries, including the Tungabhadra, Koyna, and Bhima rivers. The Krishna river basin is important for irrigation and hydroelectric power generation.
- Kaveri River: The Kaveri (Cauvery) River starts in the Western Ghats of Karnataka and flows through Karnataka and Tamil Nadu before emptying into the Bay of Bengal. It is one of the most important rivers in southern India and is crucial for agriculture in the region.
- Narmada River: The Narmada River flows primarily through the states of Madhya Pradesh and Gujarat. It originates in Amarkantak in Madhya Pradesh and flows westwards into the Arabian Sea. The Narmada river basin is known for its scenic beauty and the famous marble rocks at Bhedaghat near Jabalpur.
- Tapti River: The Tapti River also originates from the Satpura Range in Madhya Pradesh and flows westwards through Maharashtra and Gujarat before emptying into the Arabian Sea. The Tapti basin is known for its cotton-growing regions.
- Mahanadi River: The Mahanadi River originates from the Chhattisgarh region and flows eastwards through the states of Chhattisgarh and Odisha before entering the Bay of Bengal. The Mahanadi basin is significant for agriculture and irrigation.
- Sabarmati River: The Sabarmati River flows through the states of Rajasthan and Gujarat. It originates in the Aravalli Range and passes through the city of Ahmedabad before reaching the Gulf of Khambhat.
- Mahi River: The Mahi River originates in Madhya Pradesh and flows through Rajasthan and Gujarat before emptying into the Gulf of Khambhat.
These are some of the major rivers in India’s Peninsular drainage system. Each river plays a crucial role in the region’s ecology, agriculture, and livelihoods of the people living along their banks. However, like the Himalayan rivers, the Peninsular rivers also face challenges related to pollution, over-extraction of water, and environmental degradation, which require concerted efforts for conservation and sustainable management.
Difference Between Himalayan and Peninsular drainage systems
| Aspect | Himalayan Drainage System | Peninsular Drainage System |
| Location | Northern and Northeastern India | Southern and Central India |
| Source of Origin | Himalayan glaciers and Tibet Plateau | Western Ghats, Eastern Ghats, and Central Highlands |
| River Length | Longer rivers with a few exceptions | Shorter rivers |
| River Flow Direction | Mainly flows north to south | Mainly flows east or southeast |
| Seasonal Variation in Flow | Many perennial rivers with steady flow throughout year | Seasonal rivers with variable flow due to monsoons |
| River Characteristics | Often turbulent, with rapids and waterfalls | Calmer flow, less turbulent |
| Geological Age | Relatively young and geologically active | Relatively older and more stable geologically |
| Water Source | Depend heavily on snowmelt and monsoon rains | Depend on monsoon rains and local precipitation |
| Major River Basins | Ganga, Brahmaputra, Indus, Yamuna, etc. | Godavari, Krishna, Kaveri, Narmada, Mahanadi, etc. |
| Importance to Agriculture | Support extensive fertile plains and agriculture | Crucial for agriculture in the Deccan plateau |
| Hydroelectric Power Generation | Potential for large-scale hydroelectric projects | Fewer opportunities for large-scale hydro projects |
| Human Population Density | Higher population density along river banks | Relatively lower population density |
| Economic Importance | Major trade and transport routes | Important for regional trade and irrigation |
| Tourism | Attracts tourists for scenic beauty and adventure sports | Offers scenic landscapes and water-based tourism |
