Class 9th CBSE - Geography Lecture Notes: Drainage System

Introduction

• Topic: Drainage System
• Interesting Name: Refers to river systems
• Key Focus: Understanding drainage, river systems, tributaries, and distributaries.

Key Concepts

Drainage System

• Definition: An area covered by a river system is termed as a drainage basin.
• Components:
  • Rivers: Mainstream with tributaries and distributaries.
  • Tributaries: Smaller rivers or streams that flow into a larger river.
  • Distributaries: Small streams that branch out from the main river.

Water Divide

• Definition: Elevated area that separates two drainage basins.
• Example: Mountain ranges acting as divides between river systems.
• Function: Prevents rivers from mixing, guiding their flow in different directions.

Types of Drainage Patterns

1. Dendritic Pattern: Resembles tree branches, commonly formed in homogeneous rock.
2. Trellis Pattern: Develops in areas with alternating soft and hard rocks.
3. Rectangular Pattern: Occurs in regions with jointed rocks forming right angles.
4. Radial Pattern: Rivers flow outward in different directions from a central point like a mountain peak.

Indian Drainage System

Major River Systems

• Himalayan Rivers: Include Indus, Ganga, Brahmaputra.
• Peninsular Rivers: Include Narmada, Tapi, Godavari, Krishna, and Kaveri.

Himalayan River Characteristics

• Origin: Glaciers in the Himalayas.
• Nature: Perennial, fed by snowmelt and monsoon rains.
• Significant Rivers: Indus, Ganga, Brahmaputra.
• Drainage Pattern: Often forms meanders, ox-bow lakes, and floodplains.

Peninsular River Characteristics

• Origin: Mainly from the Western Ghats.
• Nature: Seasonal, primarily rain-fed.
• Significant Rivers: Narmada, Tapi, Godavari, Krishna, Kaveri.
• Drainage Pattern: Exhibit both radial and trellis patterns.

Specific River Systems

Indus River System

• Origin: Tibet near Lake Mansarovar.
• Course: Passes through Ladakh, enters Pakistan.
• Tributaries: Jhelum, Chenab, Ravi, Sutlej, Beas.
• Significance: One of the longest rivers in the world.

Ganga River System

• Origin: Confluence of Bhagirathi and Alaknanda at Devprayag, Uttarakhand.
• Course: Flows through Northern Plains, joins Brahmaputra in Bangladesh.
• Tributaries: Yamuna, Ghaghara, Gandak, Kosi.
• Significance: Vital for agriculture, forms Ganges Delta.

Brahmaputra River System

• Origin: Chemayungdung Glacier, Tibet.
• Course: Arunachal Pradesh, Assam, enters Bangladesh.
• Significance: Known for heavy silt deposits, forms Sundarbans Delta.

Peninsular River Systems

• Narmada and Tapi: Flow westwards, through rift valleys.
• Godavari, Krishna, Kaveri: Flow eastwards, form deltas on the coast.

Lakes in India

Types of Lakes

1. Glacial Lakes: Formed by glaciers, mainly in the Himalayas (e.g., Dal Lake).
2. Tectonic Lakes: Formed by earth movements (e.g., Wular Lake).
3. Lagoon Lakes: Formed by sandbars along coastal areas (e.g., Chilika Lake).
4. Ox-Bow Lakes: Formed by meanders in river courses.

Importance of Lakes

• Water Supply: Source of drinking water and irrigation.
• Tourism: Attracts tourists, boosting the local economy.
• Biodiversity: Habitat for various aquatic life forms.

Economic Significance of Rivers and Lakes

• Irrigation: Support agriculture by providing water.
• Hydropower: Source of hydroelectric energy.
• Navigation: Facilitates transportation and trade.
• Tourism: Scenic beauty and recreational activities.

River Pollution

• Causes: Industrial waste, domestic sewage, agricultural runoff.
• Effects: Degradation of water quality, harm to aquatic life.
• Prevention: Government initiatives like the National River Conservation Plan.

Conclusion

Understanding the geography and functioning of river and lake systems is crucial for sustainable management and conservation efforts. They play a vital role in supporting life, agriculture, and the economy of India.