Drainage System | Class 11 Geography Notes

Indian Drainage System: Classification and Overview

The Indian drainage system is vast and complex, shaped by the country's diverse physiographic units and precipitation patterns. It can be classified on various bases. One important classification is based on the direction of water discharge into the sea:

(i) Arabian Sea Drainage: Rivers that discharge their waters into the Arabian Sea. These include the Indus, Narmada, Tapi, Mahi, and Periyar among others.

(ii) Bay of Bengal Drainage: Rivers that discharge into the Bay of Bengal. This group includes the Ganga, Brahmaputra, Mahanadi, Krishna, Godavari, and many others.

The dividing line between these two drainage systems is formed by the Delhi Ridge, the Aravalis, and the Sahyadris, which act as a water divide.

In terms of area, about 77% of the drainage area of India, including the Ganga, Brahmaputra, Mahanadi, and Krishna, drains into the Bay of Bengal, while the remaining 23% drains into the Arabian Sea.

Another classification is based on the size of the watershed:

(i) Major River Basins: Catchment area more than 20,000 sq. km. There are 14 such basins including the Ganga, Brahmaputra, Krishna, Tapi, Narmada, and others.

(ii) Medium River Basins: Catchment area between 2,000 and 20,000 sq. km. There are 44 such basins.

(iii) Minor River Basins: Catchment area less than 2,000 sq. km. These are numerous and mostly found in low rainfall areas.

Geographically, many rivers originate in the Himalayas and flow either eastwards into the Bay of Bengal or westwards into the Arabian Sea. Large rivers on the Peninsular plateau mostly originate from the Western Ghats and flow eastwards into the Bay of Bengal. The Narmada and Tapi are exceptions, flowing westwards into the Arabian Sea.

Based on origin, nature, and characteristics, the Indian drainage system is broadly classified into two major systems:

• Himalayan Drainage System
• Peninsular Drainage System

This classification, though with some exceptions, is widely accepted and forms the basis of further study.

📊 Diagram: Figure 3.2 : Major Rivers of India

🧪 Activity: Identify rivers originating from the Himalayas and the Western Ghats on the map and classify them based on their drainage direction.

🔗 Connection: This section sets the stage for detailed study of the Himalayan and Peninsular drainage systems in the subsequent sections.