Drainage System| Chapter 3 Class 11 Geography Notes

Class 11 Geography Chapter 3 Drainage System: Drainage System is the third chapter in CBSE Class 11 Geography, which discusses the concept of Drainage systems. The notes provided for Class 11 Geography Chapter 3 on Drainage Systems are helpful for students. They are made by subject experts who simply explain things. These notes talk about different types of rivers in India, like the ones from the Himalayas and the ones from the Peninsular region.

They also explain important topics like major river basins and why lakes are important. By reading these notes, students can easily understand how rivers work and why they’re important. It makes learning about rivers and drainage much easier for students.

Drainage System| Chapter 3 Class 11 Geography Notes

Drainage

Drainage refers to the way water moves through an area, usually involving rivers, streams, and other bodies of water. In simple terms, it’s how water flows from one place to another, often ending up in larger bodies of water like lakes, seas, or oceans. This process is crucial for maintaining water balance in ecosystems and supporting life.

This chapter will teach you about India’s drainage system. It also covers topics like lakes, why they’re important, how rivers help the economy, and issues like river pollution.

When we talk about the land drained by one river system, we call it a drainage basin. A high area, like a mountain or an upland, that separates two drainage basins is called a water divide.

Drainage Systems in India

Indian rivers fall into two main categories:

1. Himalayan Rivers

• Most Himalayan rivers flow continuously throughout the year, meaning they have water all year round.
• These rivers get their water from both rainfall and melting snow from the tall mountains.
• The major Himalayan rivers like the Indus and the Brahmaputra start their journey from the northern parts of the mountain ranges.
• They usually have long journeys from where they start to where they meet the sea.

2. Peninsular Rivers

• Peninsular rivers are more dependent on seasonal rainfall.
• They mainly originate in the Western Ghats and flow towards the Bay of Bengal.
• Compared to Himalayan rivers, these rivers have shorter and less deep courses.

The Himalayan Rivers

The major Himalayan rivers include the Indus, the Ganga, and the Brahmaputra. A river, along with all its smaller rivers that flow into it, is known as a river system.

1. The Indus River System

• The Indus is among the world’s longest rivers, stretching about 2900 km.
• Originating in Tibet near Lake Mansarovar, it enters India in the Ladakh district of Jammu and Kashmir, forming a scenic gorge.
• The Satluj, Beas, Ravi, Chenab, and Jhelum rivers converge near Mithankot in Pakistan to join the Indus.

2. The Ganga River System

• The Ganga’s source, known as the ‘Bhagirathi,’ starts from the Gangotri Glacier and meets the Alaknanda at Devaprayag in Uttarakhand.
• Emerging from the mountains at Haridwar, the Ganga is fed by numerous tributaries from the Himalayas, including major rivers like the Yamuna, Ghaghara, Gandak, and Kosi.
• The Ganga stretches over 2500 km and splits into two at Farakka in West Bengal. One branch, called the Bhagirathi-Hooghly, flows southwards to the Bay of Bengal, while the mainstream flows into Bangladesh, eventually merging with the Brahmaputra to form the Meghna River, which flows into the Bay of Bengal and creates the Sundarban Delta.

3. The Brahmaputra River System

• Originating in Tibet east of Lake Mansarovar, the Brahmaputra is slightly longer than the Indus.
• After reaching Namcha Barwa (7757 m), it takes a sharp turn and enters India in Arunachal Pradesh, known as the Dihang.
• Joining with the Dibang, Lohit, and other tributaries in Assam, it forms the Brahmaputra.

Peninsular Drainage System

The drainage system of the Peninsular region predates the Himalayan drainage system, as indicated by the wide, mostly even valleys and the developed nature of the rivers. Acting as a watershed, the Western Ghats separate the major Peninsular rivers, with most flowing eastward into the Bay of Bengal and smaller streams joining the Arabian Sea. With the exception of the Narmada and Tapi rivers, which flow from east to west, the majority of Peninsular rivers flow in the opposite direction. Some rivers like the Chambal, Sind, Betwa, Ken, and Son originate in the northern part of the Peninsula and are part of the Ganga river system. Other significant river systems in the Peninsular region include the Mahanadi, Godavari, Krishna, and Kaveri. These rivers typically have fixed courses, lack meanders, and exhibit non-perennial water flow, although the Narmada and Tapi rivers, flowing through rift valleys, deviate from this pattern.

Evolution of Peninsular Drainage System

Three significant geological events in the ancient past have played a crucial role in shaping the current drainage systems of Peninsular India: (i) During the early tertiary period, the western flank of the Peninsula subsided, causing it to sink below the sea level. This event disrupted the symmetrical layout of rivers on both sides of the original watershed. (ii) The upheaval of the Himalayas led to subsidence of the northern flank of the Peninsular block and subsequent trough faulting. Rivers like the Narmada and Tapi flow in these trough faults, filling the original cracks with their sedimentary materials. As a result, these rivers lack significant alluvial and deltaic deposits. (iii) There was a slight tilting of the Peninsular block from northwest to southeast direction during the same period, which influenced the entire drainage system to orient towards the Bay of Bengal.

River Systems of Peninsular Drainage

In Peninsular India, the main water divide is formed by the Western Ghats. Most major rivers of the Peninsula, such as the Mahanadi, Godavari, Krishna, and Kaveri, flow eastwards and drain into the Bay of Bengal, forming deltas at their mouths. The Narmada and the Tapi are the only long rivers that flow west and create estuaries.

The Narmada Basin

• Originating in the Amarkantak hills in Madhya Pradesh, the Narmada flows through a deep gorge near Jabalpur known as the ‘Marble Rocks’.
• At Dhuadhar Falls, the river cascades over steep rocks.
• The Narmada basin covers parts of Madhya Pradesh and Gujarat.

The Tapi Basin

• Rising in the Satpura ranges in the Betul district of Madhya Pradesh, the Tapi basin spans parts of Madhya Pradesh, Gujarat, and Maharashtra.

The Godavari Basin

• The Godavari, the largest Peninsular river with a length of about 1500 km, originates from the Western Ghats in Maharashtra.
• Its basin covers parts of Maharashtra, Madhya Pradesh, Odisha, and Andhra Pradesh, and it is joined by numerous tributaries like the Purna, Wardha, Pranhita, Manjra, Wainganga, and Penganga. Due to its length and coverage area, it’s also called the Dakshin Ganga.

The Mahanadi Basin

• Rising in the highlands of Chhattisgarh, the Mahanadi spans about 860 km and its basin is shared by Maharashtra, Chhattisgarh, Jharkhand, and Odisha.

The Krishna Basin

• Originating near Mahabaleshwar, the Krishna river extends about 1400 km and drains parts of Maharashtra, Karnataka, and Andhra Pradesh.

The Kaveri Basin

• The Kaveri originates from the Brahmagri range of the Western Ghats and stretches approximately 760 km in length.
• Its basin covers areas of Karnataka, Kerala, and Tamil Nadu. Apart from these significant rivers, there are smaller ones that flow towards the east, including the Damodar, Brahmani, Baitarni, and Subarnrekha.

Lakes

India has many lakes, each varying in size and characteristics.

• Many lakes in India are permanent, while others only hold water during the rainy season.
• Some lakes are formed by the action of glaciers and ice sheets, while others result from wind, river activity, and human interventions.

Tourists are drawn to lakes in picturesque destinations like Srinagar and Nainital. Here’s is a different types of lakes:

• Ox-bow lakes are created when a meandering river forms cut-offs across a floodplain.
• Coastal areas often feature lagoons formed by spits and bars, such as Chilika Lake, Pulicat Lake, and Kolleru Lake.
• Lakes in regions of inland drainage can be seasonal, like Sambhar Lake in Rajasthan, which is used for salt production.

The Himalayan region harbors most freshwater lakes, primarily of glacial origin. Wular Lake in Jammu and Kashmir, the largest freshwater lake in India, resulted from tectonic activity. Other notable freshwater lakes include Dal Lake, Bhimtal, Nainital, Loktak, and Barapani.

Extent of Usability of River Water

Rivers in India carry substantial volumes of water annually, but this distribution is uneven both in time and space. While some rivers flow perennially, providing water throughout the year, others are non-perennial and experience low water levels during the dry season. During the monsoon season, a significant amount of water is lost to floods, with excess water flowing into the sea. Consequently, areas experiencing floods may coexist with regions suffering from drought. This phenomenon arises from challenges in both water resource availability and management. Mitigating the issues of floods and droughts simultaneously requires strategic measures.

One potential solution is the transfer of surplus water from water-rich basins to water-deficit basins. Inter-basin water transfer schemes have been proposed to address this imbalance. However, the implementation of such schemes faces various challenges. For instance, simply digging canals may not suffice due to the uneven terrain. The north Indian rivers, which often have surplus water, may require mechanisms to lift water from the plains to the plateau areas.

To facilitate a comprehensive understanding of the issue, organizing a debate can be beneficial. Participants can discuss and analyze various aspects, including the ranking of problems associated with river water usage. These problems may include insufficient water availability, river water pollution, silt accumulation, uneven seasonal flow, interstate water disputes, and channel shrinkage due to settlement expansion towards riverbeds.

River pollution is a significant concern caused by various human activities such as industrial discharge, waste disposal, religious practices, and urban runoff. Initiatives like the Ganga Action Plan and campaigns for cleaning rivers like the Yamuna in Delhi aim to address this issue. Collecting information on such pollution control schemes and presenting them in a comprehensive write-up can help raise awareness and guide further actions towards making rivers pollution-free.

FAQs on Class 11 Geography Chapter 3 Drainage System

What is drainage?

Drainage refers to the system of rivers and streams that drain excess water from an area, ultimately leading to larger bodies of water like oceans, seas, or lakes.

What are the two main types of river systems in India?

The two main types of river systems in India are Himalayan rivers and Peninsular rivers.

How do Himalayan rivers differ from Peninsular rivers?

• Himalayan rivers are mostly perennial, meaning they flow throughout the year, while Peninsular rivers are mostly seasonal, dependent on rainfall.
• Himalayan rivers have long courses originating from high mountain ranges, whereas Peninsular rivers have shorter courses and flow towards the Bay of Bengal.

Can you name some major Himalayan rivers and their characteristics?

Major Himalayan rivers include the Indus, Ganga, and Brahmaputra. They have long courses, originate from the north of mountain ranges, and receive water from rainfall and melted snow.

What are some characteristics of Peninsular rivers?

Peninsular rivers flow eastwards and drain into the Bay of Bengal. They are mostly seasonal, originating from the Western Ghats, and form deltas at their mouths.

What are the important river basins in India?

Some important river basins in India include the Indus Basin, Ganga Basin, Brahmaputra Basin, Godavari Basin, Krishna Basin, and Kaveri Basin.