Understanding Drainage and Drainage Patterns

• Drainage refers to the natural flow of water through rivers, streams, and other channels that collect and transport water from land to seas or other water bodies.
• Drainage Patterns describe the arrangement and organization of rivers and streams in a given area. These patterns are determined by topography, geological structure, slope, and soil type.

Types of Drainage Patterns:

1. Dendritic Pattern:

   • This pattern resembles the branches of a tree, where smaller streams join to form larger rivers, typical in regions with uniform rock structures.
   • Example: The Northern Plains of India exhibit this pattern in rivers like the Ganga.

2. Radial Pattern:

   • Here, rivers flow outward from a central high point, such as a hill or mountain, spreading in different directions.
   • Example: Seen in rivers originating from Amarkantak Hill in Madhya Pradesh.

3. Trellis Pattern:

   • A pattern in which parallel main rivers are joined by tributaries at right angles. This pattern occurs in folded mountain regions with alternating bands of hard and soft rock.
   • Example: Found in the Chotanagpur Plateau.

4. Centripetal Pattern:

   • Rivers flow inward toward a central depression or basin, converging at a single point.
   • Example: Seen in the Loktak Lake basin in Manipur.

River Basins and Watersheds

1. A River Basin is the entire geographical area drained by a river and its tributaries. It includes all land that contributes water to the main river.
   • Example: The Ganga Basin spans multiple states and is critical for agriculture and livelihoods.
2. A Watershed is a smaller land area within a basin, divided by ridges that direct the flow of water to specific rivers or streams. It acts as a boundary that separates two basins.
   • Watersheds influence water availability, flood control, and soil conservation.

India has twenty major river basins, categorized primarily by their discharge into either the Bay of Bengal or the Arabian Sea.

Major Basins:

1. Arabian Sea Basin:
   • Covers about 23% of India’s area, with rivers like the Indus, Narmada, and Tapi.
2. Bay of Bengal Basin:
   • Comprises 77% of India’s drainage, including major rivers like the Ganga, Brahmaputra, and Mahanadi.

Classification of Indian Rivers

Indian rivers are classified into two broad categories: the Himalayan rivers and the Peninsular rivers, each with distinct characteristics.

Himalayan Drainage System

• The Himalayan rivers originate from glaciers and snowfields, providing them with a perennial flow of water throughout the year.
• Young Rivers: These rivers are relatively young, allowing them to carve deep valleys, gorges, and V-shaped channels through erosion.

Main Rivers:

1. Indus River System:
   • Originates near Mansarovar Lake in Tibet. It enters India and flows through Jammu & Kashmir before reaching Pakistan.
   • Major tributaries in India include the Jhelum, Chenab, Ravi, Beas, and Sutlej.
   • Historically significant, the Indus Valley Civilization developed along its banks.
2. Ganga River System:
   • Begins at the Gangotri Glacier and flows southeast through northern India, forming a fertile plain.
   • Tributaries include:
     • Yamuna: Originates from Yamunotri Glacier, meets the Ganga at Allahabad.
     • Ghaghara, Gandak, and Kosi: Flow from Nepal and join the Ganga in the plains, contributing to flood conditions due to sediment load.
   • Deltas: The Ganga forms the largest delta in the world, known as the Sundarbans Delta, shared with Bangladesh.
3. Brahmaputra River System:
   • Known as the Tsangpo in Tibet, it enters India as the Siang and becomes the Brahmaputra in Assam.
   • Flows through a braided channel and is known for flooding and river meandering.
   • Joins the Ganga in Bangladesh, forming the Meghna before flowing into the Bay of Bengal.

Peninsular Drainage System

• The Peninsular rivers are much older and more stable, primarily fed by monsoon rains, making them non-perennial.
• These rivers have wide valleys, and their courses are often influenced by the tilt and slope of the land.

1. Narmada and Tapi:

   • Flow westward through rift valleys created by faulting, which is rare for Peninsular rivers.
   • The Narmada and Tapi both empty into the Arabian Sea, with the Narmada flowing between the Satpura and Vindhya ranges.

2. Godavari:

   • Known as the Dakshin Ganga due to its size, it originates in the Western Ghats and flows eastward into the Bay of Bengal.
   • It has a large basin covering multiple states and forms a significant delta.

3. Krishna and Kaveri:

   • Both originate in the Western Ghats and flow eastward, creating fertile deltas before emptying into the Bay of Bengal.
   • Kaveri is known for its water disputes between states due to its importance for irrigation and drinking water.

4. Mahanadi:

   • Flows through Chhattisgarh and Odisha, forming a large delta known for its fertile alluvium.

Importance of Drainage Systems

The drainage systems are crucial for various reasons:

• Agriculture: River basins, especially the Ganga and Brahmaputra plains, are highly fertile and support extensive agriculture, contributing to India’s food supply.
• Irrigation: Major river projects, like the Bhakra Nangal Dam on the Sutlej and the Hirakud Dam on the Mahanadi, provide water for irrigation and help stabilize water supply during dry periods.
• Flood Control: Rivers, especially those in the Himalayan region, can cause flooding due to snowmelt and heavy monsoon rains. Drainage planning and river embankments are essential to prevent disasters.
• Hydropower: Rivers in mountainous regions offer significant potential for hydropower generation, as seen in projects on the Bhagirathi, Alaknanda, and Sutlej rivers.
• Navigation and Trade: Rivers facilitate inland navigation and trade, particularly in the Godavari-Krishna delta and the Sundarbans in West Bengal.

Summary

India’s diverse drainage system encompasses the perennial, young, and dynamic Himalayan rivers and the older, monsoon-dependent Peninsular rivers. Understanding these systems is vital for water resource management, agriculture, flood control, and energy production. India’s rivers not only shape its landscapes but also play a crucial role in sustaining life and economic activities across the country.