Drainage
- Rivers have always held immense importance for humans, serving as vital resources for habitation, irrigation, transportation, power generation, and recreational activities.
- A river or stream refers to a body of water that flows within a channel.
- The term “Drainage” describes the river system of a particular area, which encompasses the main river and its tributaries, collecting and channeling surface water towards the sea.
- The region drained by a single river system is called a drainage basin, while the boundary separating one drainage basin from another is known as the watershed.
- The catchment area, also known as the “river basin” for larger rivers or “watershed” for smaller rivulets and rills, refers to the specific region from which a river collects water.
- Watersheds are generally smaller in size compared to river basins, which cover larger areas.
Drainage Pattern
- The geometric arrangement of streams in a particular region, influenced by factors such as slope, varying rock resistance to weathering and erosion, climate, hydrological variations, and landscape structure, is referred to as a drainage pattern.
- Antecedent rivers are those that existed before the upliftment of the Himalayas and carved gorges in the mountains. Examples of antecedent rivers include the Indus, Sutlej, and Ganges.
- Consequent rivers are those that follow the general slope of the terrain, such as the Godavari and Krishna rivers that descend from the Western Ghats.
- A dendritic drainage pattern resembles the branches of a tree and is commonly found in the rivers of the northern plains.
- It develops when the river channel aligns with the slope of the land. Radial drainage patterns occur when rivers originate from a central hill or point and flow outward in various directions.
- The rivers originating from the Amarkantak range exemplify this pattern. Trellis drainage patterns occur when primary tributaries flow parallel to each other, and secondary tributaries join them at right angles.
- This pattern emerges when there are alternating layers of hard and soft rocks running parallel to each other.
- The right bank tributaries of the Brahmaputra River display a trellis pattern, while the left bank tributaries exhibit a dendritic pattern. Centripetal drainage patterns occur when rivers discharge their waters from all directions into a lake or depression.
- This pattern is the opposite of radial drainage and is commonly found in areas with karst topography.
- It is possible to find a combination of several drainage patterns within the same drainage basin
Dendritic Drainage Pattern:
- This is the most common pattern, resembling the branching of tree roots. It develops where the river channel follows the terrain’s slope, typically in areas with rock structures that erode uniformly in all directions. Tributaries join larger streams at acute angles (less than 90°).
- Examples include the rivers of the northern plains: Indus, Ganga, and Brahmaputra.
Parallel Drainage Pattern:
- This pattern forms in regions with parallel, elongated landforms and a noticeable surface slope. Tributary streams run parallel to the surface’s slope.
- Examples include the rivers originating in the Western Ghats: Godavari, Kaveri, Krishna, and Tungabhadra.
Trellis Drainage Pattern:
- Found in folded topography with parallel hard and soft rocks. Valleys in down-turned folds called synclines house the mainstream channel. Primary tributaries flow parallel to each other, and secondary tributaries join them at right angles.
- This pattern is seen in the upper Himalayan region: Indus, Ganga, and Brahmaputra.
Rectangular Drainage Pattern:
- Occurs in regions affected by faulting, where streams follow the path of least resistance over strongly joined rocky terrain. Tributary streams make sharp bends and enter the mainstream at high angles.
- Streams in the Vindhya mountain range, such as Chambal, Betwa, and Ken, exhibit this pattern.
Radial Drainage Pattern:
- The radial drainage pattern typically takes shape around a central elevated point and is often associated with conical landforms like volcanoes. In this pattern, rivers originate from a central hill and flow in multiple directions, resembling the spokes of a wheel.
- A notable example includes the rivers stemming from the Amarkantak range, such as the Narmada and Son (a Ganga tributary).
Centripetal Drainage Pattern:
- Conversely, the centripetal drainage pattern involves streams flowing toward a central depression. During wetter seasons, these streams contribute to ephemeral lakes that tend to evaporate during drier periods. Occasionally, salt flats form in these dry lake beds when salt dissolved in the lake water precipitates as the water evaporates.
- A case in point is the Loktak Lake in Manipur.
India’s drainage system
- India’s drainage system is primarily influenced by the vast relief features of the subcontinent. The drainage system can be classified based on various factors.
- In terms of water discharge towards the sea, it can be categorized into the Arabian Sea drainage and the Bay of Bengal drainage.
- These two systems are separated by the Delhi Ridge, the Aravallis, and the Sahyadris, as indicated by a line.
- The majority of rivers in India have their origins in the Himalayas and flow into the Bay of Bengal, except for the Indus River system, which discharges into the Arabian Sea.
- Examples of rivers in this category include the Ganga, Yamuna, Gandak, Tista, and Brahmaputra.
- Large rivers that flow on the Peninsular plateau have their sources in the Western Ghats and discharge their waters into the Bay of Bengal.
- Rivers like Krishna, Godavari, Kaveri, and Tungabhadra fall into this category. However, there are exceptions like the Narmada and Tapi rivers, along with several smaller rivers, which discharge their waters into the Arabian Sea.
- These smaller rivers originated in the Western Ghats, such as the Mandavi, Netravati, Sharavati, and Periyar rivers.
- Approximately 77% of the drainage area, including rivers like Ganga, Brahmaputra, Mahanadi, and Krishna, is oriented towards the Bay of Bengal, while the remaining 23% comprises systems like Indus, Narmada, Tapi, Mahi, and Periyar, which discharge their waters into the Arabian Sea.
- Based on their origin, India’s drainage can be divided into the Himalayan drainage and the Peninsular drainage. However, it should be noted that some Peninsular rivers such as the Chambal, Betwa, Ken, and Son are tributaries of the Ganga river system, originating in the Himalayas.
- India’s drainage basins are further categorized based on the size of the watershed. There are three categories: major river basins with an over 20,000 sq. km catchment area.
- which includes 14 basins like Ganga, Indus, Godavari, Krishna, Brahmaputra, Mahanadi, Narmada, Kaveri, Tapi, Pennar, Brahmani, Mahi, Sabarmati, Barak, and Suvarnarekha; medium river basins with a catchment area between 2,000-20,000 sq. km, encompassing 44 basins like Kalindi, Periyar, Meghna, etc.; and minor river basins with a catchment area less than 2,000 sq. km, comprising several rivers that flow in areas with low rainfall.
FAQs
Q1. What is the drainage pattern of the Ganga River in India?
Ans. The Ganga River has a dendritic drainage pattern, characterized by the river and its tributaries resembling the branches of a tree. The Ganga, with its numerous tributaries such as the Yamuna, Ghaghara, Gandak, and Kosi, forms an extensive network that covers a significant portion of northern India. This drainage pattern facilitates the efficient flow of water and sediment, contributing to the fertility of the plains and the agricultural productivity of the region.
Q2. Where can I find comprehensive notes on the drainage system of India?
Ans. Comprehensive notes on the drainage system of India can be found in various academic textbooks on geography, hydrology, and environmental studies. Additionally, many reputable educational websites and online platforms dedicated to geography and environmental sciences offer detailed information and study materials on the drainage patterns and river systems of India.
Q3. What is the drainage pattern of the Indus River, and what are its notable characteristics?
Ans. The Indus River has a trellis drainage pattern, characterized by the river and its tributaries forming a series of parallel streams. The Indus, along with its tributaries such as the Jhelum, Chenab, Ravi, Beas, and Sutlej, flows through the northwestern region of India, primarily in the state of Jammu and Kashmir and the Punjab region. This pattern is shaped by the topography of the region, which consists of alternating parallel ridges and valleys.
Q4. What is unique about the drainage system of North East India?
Ans. The drainage system of North East India is characterized by the presence of numerous rivers and their tributaries, including the Brahmaputra, Barak, and their respective tributaries. This region is known for its high rainfall and complex topography, resulting in a dendritic and radial drainage pattern. The Brahmaputra River, one of the major rivers in the region, has a significant impact on the socio-economic and ecological aspects of North East India, supporting agriculture, fisheries, and transportation.
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