Drainage system and watersheds

Introduction

A drainage system is a critical component of the earth’s hydrological cycle. It refers to the network of channels through which water flows, including main rivers, tributaries, and smaller streams, ultimately forming a complete system. Understanding drainage systems and watersheds is essential for managing water resources, flood control, and understanding geological features. In India, the drainage system can be broadly classified into two main types: the Himalayan drainage system and the Peninsular drainage system. Each of these drainage systems has distinct characteristics, patterns, and river systems that play a crucial role in shaping the landscape.

Drainage System

What is a Drainage System?

• A drainage system is the entire network of interconnected channels that help in draining water from land.
• It includes the main river along with all its tributaries that carry water to a larger body such as a lake, sea, or ocean.
• Examples of well-known drainage systems in India include:
  • Indus River System (Indus Drainage System)
  • Ganga Drainage System
  • Godavari Drainage Basin

Types of Drainage Systems in India

1. Himalayan Drainage System
2. Peninsular Drainage System

Drainage Pattern

What is a Drainage Pattern?

• Within a drainage basin, streams form a certain pattern based on the land’s slope, rock structure (hard or soft), and climatic conditions.
• The drainage pattern provides insights into the rock types, geological structures, and other factors influencing the flow of water.

Examples of Drainage Patterns

1. Dendritic Pattern
   • Forms in flat topography with uniform bedrock.
   • Appears like the branches of a tree.
2. Radial Pattern
   • Seen in regions with high land such as volcanic mountains.
   • Streams flow outward from a central peak.
3. Rectangular Pattern
   • Develops in areas with faulted or jointed rock structures.
   • Streams and rivers take sharp bends, often at right angles.

Types of Drainage Patterns

Dendritic Drainage Pattern

• Description: Resembles the shape of a tree with branches.
• Formation: Develops where the river channels follow the slope of the terrain.
• Examples: Indus, Godavari, Mahanadi, Cauvery, and Krishna.

Trellis Drainage Pattern

• Description: Small tributaries join the main river at right angles.
• Formation: Occurs where hard and soft rocks lie parallel to each other, leading to differential erosion.
• Example: The Yamuna flowing parallel to the Ganga and joining it at right angles.

Rectangular Drainage Pattern

• Description: The main stream bends at right angles with tributaries joining at similar angles.
• Formation: Develops on jointed terrain with faulted rocks.
• Example: Vindhya Mountains.

Radial Drainage Pattern

• Description: Rivers flow in different directions from a central peak or dome-like structure.
• Formation: Seen around volcanic mountains or domes.
• Example: Amarkantak plateau with rivers like Narmada, Tapi, Son, Chambal, and Mahanadi originating in different directions.

Centripetal Drainage Pattern

• Description: Streams flow from all directions into a central depression.
• Formation: Common in regions with central depressions such as lakes or basins.
• Example: Loktak Lake in Manipur.

Himalayan Drainage System

Evolution of Himalayan Rivers

• The evolution of the Himalayan rivers has multiple theories.
• Approximately 5 to 25 million years ago, a large river known as the Shiwalik or Indo-Brahma River stretched from Assam to Punjab, discharging into the Gulf of Sindh.
• Major geological upheavals in the Pleistocene epoch led to significant changes in the river courses, especially in the Western Himalayas and Potwar Plateau.

Characteristics of Himalayan Rivers

• Water Source: Fed by melting snow and precipitation, making them perennial.
• Antecedental Nature: Older rivers maintain their courses despite the uplift of the Himalayan region.
• Erosion Features: Deep gorges, V-shaped valleys, and waterfalls are prominent in mountainous areas.
• Deposition Features: As rivers enter the plains, they form flat valleys, oxbow lakes, floodplains, deltas, and braided channels.
• High Erosion: Intense erosion occurs in the upper courses, while the lower courses often witness river courses changing frequently.

Peninsular Drainage System

Evolution of Peninsular Rivers

• The Peninsular drainage system is older than the Himalayan drainage system.
• Three major geological events shaped this drainage system:
  • Subsidence of the western part of the peninsula under the sea during the Tertiary period.
  • The upliftment of the Himalayas and subsidence in the northern part.
  • The tilting of the Peninsular block from northwest to southeast, causing rivers to flow towards the Bay of Bengal.

East Flowing Rivers

• Rivers that discharge into the Bay of Bengal.
• Examples:
  • Damodar: Flows through the eastern part of India.
  • Mahanadi: Originates in Chhattisgarh, flowing through Odisha.
  • Godavari: Largest river system in Peninsular India, originating in Maharashtra.
  • Krishna: Second largest east-flowing river, starting from Sahyadri.
  • Cauvery: Originates in Karnataka, flowing through Tamil Nadu.
  • Others include Subarnarekha, Brahmani, Penner, Palar, and Vaigai.

West Flowing Rivers

• Rivers that discharge into the Arabian Sea.
• Examples:
  • Luni: The largest river system in Rajasthan.
  • Sabarmati and Mahi: Flow through the western parts of India.
  • Narmada: Originates from the Amarkantak plateau, flowing through a rift valley.
  • Tapi: Flows parallel to the Narmada, originating from Madhya Pradesh.
  • Other rivers include Mandovi, Zuari, Sharavati, Bharathapuzha, Periyar, and Pamba.

Himalayan vs Peninsular Rivers

Origin

• Himalayan Rivers: These rivers originate from mountains and glaciers, making them naturally rich in water.
• Peninsular Rivers: These rivers primarily arise from highlands and plateaus.

Water Availability

• Himalayan Rivers: Perennial in nature, as they are fed by melting glaciers and rainfall throughout the year.
• Peninsular Rivers: Seasonal in nature, primarily dependent on monsoon rains, which results in variations in water availability.

Drainage Patterns

• Himalayan Rivers: Typically form dendritic patterns resembling a branching tree, influenced by the slope and terrain.
• Peninsular Rivers: Often exhibit radial and rectangular drainage patterns due to the plateau’s structure and geological formations.

Drainage Types

• Himalayan Rivers: Examples of antecedent rivers that existed before the upliftment of land and maintain their course despite geological changes.
• Peninsular Rivers: Examples of consequent rivers that follow the natural slope of the terrain formed over time.

Basin Size

• Himalayan Rivers: Have extensive and large basins due to their extensive river networks.
• Peninsular Rivers: Tend to have relatively smaller basins with limited tributaries.

East-Flowing vs West-Flowing Rivers

Length and Direction

• East-Flowing Rivers: Generally longer in length and flow towards the Bay of Bengal.
• West-Flowing Rivers: Comparatively shorter and flow towards the Arabian Sea.

Discharge Points

• East-Flowing Rivers: Empty into the Bay of Bengal.
• West-Flowing Rivers: Discharge into the Arabian Sea.

Relief and Slope

• East-Flowing Rivers: Have a lower relief (slope) compared to their west-flowing counterparts.
• West-Flowing Rivers: Possess a steeper slope, contributing to their shorter course.

Waterfalls and Tributaries

• East-Flowing Rivers: Rarely form waterfalls and usually have well-defined tributaries.
• West-Flowing Rivers: Frequently form waterfalls due to steep slopes and have fewer or no tributaries.

Basin Size

• East-Flowing Rivers: Have larger basins with more extensive catchment areas.
• West-Flowing Rivers: Have smaller basins with more concentrated drainage areas.

Formation of Deltas and Estuaries

• East-Flowing Rivers: Generally form deltas where they meet the sea.
• West-Flowing Rivers: Do not form deltas; instead, they create estuaries.

Watershed

What is a Watershed?

• A watershed is an area of land that includes a network of rivers and streams draining into a common point.
• It serves as a geographical unit where all the water drains into a single river, stream, lake, or reservoir.
• Watersheds can range in size from small inland lakes to thousands of miles of land containing various water bodies.

Types of Watersheds

• Micro Watershed: The smallest type of watershed.
• Milli Watershed: Slightly larger than a micro watershed.
• Mini Watershed: Intermediate in size.
• Sub-Watershed: A division within a larger watershed.
• Macro Watershed: The largest watershed, often encompassing multiple rivers and streams.

Importance of Watersheds

• They play a crucial role in irrigation by storing and supplying water to agricultural lands.
• Functions include:
  • Capturing Groundwater: Watersheds collect and store water underground.
  • Storing Groundwater: Helps maintain water levels for various uses.
  • Recharging Groundwater: Replenishes underground water sources.
  • Filtering Pollutants: Acts as a natural filtration system to improve water quality.
  • Flood Control: Securely releases rainwater to prevent flooding during heavy rainfall.

Example

• A large drainage basin, such as the Ganga or Godavari basin, serves as an example of a macro watershed.

Watershed Management

What is Watershed Management?

• Watershed management is the process of guiding and organizing land use and resources within a watershed to provide desired goods and services without harming the soil or water resources.

Views of Watershed Management

Narrow Sense

• Involves water conservation through techniques like:
  • Stopping running water.
  • Ensuring standing water sinks into the ground.
• Focuses on conserving surface and groundwater.

Broader Sense

• Involves comprehensive conservation, regeneration, and judicious use of resources, ensuring sustainable development.

Watershed Management Programs in India

• 1970: Initiated programs to manage drought-prone areas and desert development.
• Over time, central and state governments have introduced numerous watershed management projects to promote sustainable water use and conservation.

Conclusion

The Himalayan and Peninsular river systems, along with the concepts of watersheds and watershed management, play a crucial role in India’s geography, ecology, and water management. Understanding the differences between these river systems helps in efficient planning, conservation, and utilization of water resources. Proper watershed management is essential for maintaining soil health, preventing floods, ensuring water availability, and sustaining agriculture.

1. Compare and contrast the Himalayan drainage system with the Peninsular drainage system in terms of origin, characteristics, and water flow. (250 words)
2. What are the key factors that differentiate east-flowing and west-flowing rivers, and how do they affect delta formation? (250 words)
3. How does watershed management contribute to sustainable water resource utilization in India? (250 words)