Have you ever wondered where rainwater goes after it falls on the Earth? It doesn’t just disappear—it flows through streams and rivers, forming a vast drainage system. In this chapter, you will understand how rivers and lakes shape life in India.
 |
| Drainage in India – Rivers and Lakes (Class 9 Geography Chapter 3 | CBSE NCERT) |
Introduction
Have you ever thought about what happens to the water when it rains?
Does it simply disappear into the ground, or does it follow a specific path?
In reality, rainwater follows a well-organized system. It flows from small streams into larger rivers and finally reaches seas or oceans. This entire process is known as drainage.
If we observe closely, we find that human civilization has always developed around rivers. Wherever there was water, life flourished, agriculture developed, and settlements grew. Therefore, drainage is not just a geographical concept; it is the foundation of human life and development.
Table of Contents
- Concept of Drainage
- River System
- Drainage Basin and Its Importance
- Role of Water Divide
- Drainage in the Global Context
- Structure of Drainage System in India
- Introduction to Himalayan Rivers
- Nature of Himalayan Rivers
- Stages of a River
- Major Himalayan River Systems
- The Indus River System
- The Ganga River System
- The Brahmaputra River System
- Introduction to Peninsular Rivers
- Nature of Peninsular Rivers
- Direction of Flow and Water Divide
- The Narmada River System
- The Tapi River System
- The Godavari River System
- The Mahanadi River System
- The Krishna River System
- The Kaveri River System
- East-Flowing Smaller Rivers
- Introduction to Lakes
- Formation of Lakes
- Major Lakes of India
- Importance of Lakes
- Economic Importance of Rivers
- Problem of River Pollution
- Efforts for River Conservation
- Overall Conclusion
Concept of Drainage
Drainage refers to the system through which water flows across the land surface. When water from rainfall, melting snow, or other sources flows through rivers and ultimately reaches a sea, lake, or ocean, it forms a drainage system.
When we look at the physical map of India, we notice that many small streams originating from different directions come together to form large rivers. These rivers eventually drain into large water bodies.
This entire network is called a river system.
River System
A river system is not just a single river. It includes the main river along with all its tributaries and the area from which it collects water.
In simple terms, a river system consists of the main channel, its branches, and the land area that contributes water to it.
Drainage Basin and Its Importance
The area drained by a single river and its tributaries is known as the drainage basin.
This concept is very important because it determines the amount of water flowing in a river. If a region receives heavy rainfall, the river flowing through it will have more water. On the other hand, regions with less rainfall will have smaller and less water-rich rivers.
Thus, the drainage basin influences not only the river but also agriculture, water availability, and human activities in that region.
Role of Water Divide
Between two drainage basins, there is usually an elevated landform such as a hill or mountain. This elevated area is known as a water divide.
The water divide determines the direction in which water flows. Rainfall falling on one side flows into one river, while rainfall on the other side flows into another river.
This concept helps in understanding how different river systems are separated from each other.
Drainage in the Global Context
Structure of Drainage System in India
India’s drainage system is mainly controlled by its physical features. The country can be broadly divided into two major geographical regions: the Himalayan region and the Peninsular region.
Based on this division, the rivers of India are also classified into two major groups.
One group includes rivers originating from the Himalayas, while the other includes rivers originating from the Peninsular plateau. These two types of rivers differ significantly in their characteristics, origin, and flow.
Introduction to Himalayan Rivers
The rivers originating from the Himalayas are the most important rivers of India. These rivers are long and carry water throughout the year.
The reason behind this is that they receive water from two sources. One is rainfall, and the other is the melting of snow from the high Himalayan mountains. Because of this continuous supply of water, these rivers are perennial in nature.
Nature of Himalayan Rivers
In their upper course, Himalayan rivers flow with great speed. Their fast flow enables them to cut through mountains and form deep valleys known as gorges.
As these rivers move towards the plains, their speed decreases. They become wider and start depositing the fertile soil they carry with them. This process leads to the formation of highly fertile plains in northern India.
Stages of a River
A river passes through different stages during its course.
In the upper stage, the river flows through mountainous regions with high speed and causes erosion. In the middle stage, the flow becomes slower, and the river transports sediments. In the lower stage, the flow becomes very slow, and the river deposits sediments, forming features like deltas.
This progression shows how a river changes its character from source to mouth.
Major Himalayan River Systems
The Himalayan rivers are divided into three major systems. These are the Indus river system, the Ganga river system, and the Brahmaputra river system.
These three systems together form the backbone of India’s drainage network and are essential for the country’s water resources.
Real Character of Himalayan Rivers
After understanding the basic nature of Himalayan rivers, it is important to study how these rivers actually behave in different regions.
In the mountainous regions of the Himalayas, these rivers flow with great force. Due to this high speed, they have the ability to cut through hard rocks and create deep and narrow valleys known as gorges. These gorges are one of the most striking features of Himalayan rivers.
As these rivers descend from the mountains and enter the plains, their speed gradually decreases. When the speed reduces, the rivers start spreading out and begin depositing the sediments they carry. These sediments consist of fine soil, sand, and silt, which make the plains extremely fertile.
This is the reason why the Northern Plains of India are among the most fertile regions in the world.
The Indus River System
The Indus river system is one of the major river systems originating from the Himalayas. The Indus River rises near Lake Mansarovar in Tibet. From there, it flows in a north-westerly direction and enters India through the Ladakh region.
In Ladakh, the river flows through a rugged mountainous landscape and forms deep gorges. Its course in this region is marked by strong currents and steep slopes.
Several important tributaries join the Indus in this upper region, including the Zaskar, Nubra, Shyok, and Hunza rivers. These tributaries add significant volume to the river.
After flowing through India, the Indus moves into Pakistan. In this region, major tributaries such as the Satluj, Beas, Ravi, Chenab, and Jhelum join it. These rivers together form a large and complex river system.
Eventually, the Indus flows southward and empties into the Arabian Sea.
The total length of the Indus River is about 2900 kilometers, making it one of the longest rivers in the world. A large part of its basin lies in Pakistan, while a smaller portion lies in India, covering areas of Jammu and Kashmir, Ladakh, Himachal Pradesh, and Punjab.
An important aspect related to this river system is the Indus Water Treaty signed in 1960 between India and Pakistan. According to this agreement, India is allowed to use only about 20 percent of the water of the Indus system, mainly for irrigation purposes.
The Ganga River System
The Ganga river system is the most important river system in India. It holds not only geographical importance but also cultural and economic significance.
The main source of the Ganga is the Bhagirathi River, which originates from the Gangotri Glacier in the Himalayas. Another river, the Alaknanda, also originates from the Himalayas. These two rivers meet at Devprayag in Uttarakhand, and from this point onward, the river is known as the Ganga.
When the Ganga reaches Haridwar, it leaves the mountainous region and enters the plains. This marks a major change in its behavior. The river becomes wider, its flow slows down, and it begins to meander.
As the Ganga flows through the plains, many important tributaries join it. Among them, the Yamuna is the most significant. It originates from the Yamunotri Glacier and flows parallel to the Ganga before joining it at Prayagraj.
Other major tributaries include the Ghaghara, Gandak, and Kosi rivers, which originate from the Nepal Himalayas. These rivers bring a large amount of water and sediments into the Ganga.
One notable feature of the Ganga is the occurrence of floods. Every year, the river overflows in certain regions. While floods may cause damage, they also deposit fertile soil, which enhances agricultural productivity.
As the Ganga moves further east, it reaches the region near Farakka in West Bengal. Here, it divides into two branches. One branch, known as the Bhagirathi-Hooghly, flows southward, while the main stream enters Bangladesh.
Finally, the Ganga joins the Brahmaputra and forms a vast delta before emptying into the Bay of Bengal. This delta is known as the Sundarban Delta, which is the largest delta in the world. It is named after the Sundari trees found in this region.
The Brahmaputra River System
The Brahmaputra river system is another major Himalayan river system. It originates in Tibet, near the east of Lake Mansarovar. In Tibet, this river is known as the Tsangpo.
The river flows eastward parallel to the Himalayas for a long distance. Near the Namcha Barwa peak, it takes a sharp turn and enters India through Arunachal Pradesh. In this region, it is known as the Dihang.
As it enters the plains of Assam, several tributaries such as the Dibang and Lohit join it. After this confluence, the river is known as the Brahmaputra.
One of the most distinctive features of the Brahmaputra is its wide and braided channel. In Assam, the river often splits into multiple channels, forming river islands.
This river is also known for frequent floods, which cause damage to life and property. However, like the Ganga, these floods also contribute to soil fertility.
Another important characteristic of the Brahmaputra is the large amount of silt it carries. Due to heavy sediment deposition, the river often changes its course, making it highly dynamic and unpredictable.
Overall Importance of Himalayan Rivers
When we consider the Indus, Ganga, and Brahmaputra together, it becomes clear that these rivers form the backbone of India’s drainage system.
They provide water for agriculture, support large populations, and create fertile plains. Without these rivers, life in northern India would be extremely difficult.
These rivers are not just natural features; they are essential for the survival and development of the region.
Introduction to Peninsular Rivers
After understanding the Himalayan rivers, we now move to the second major group of rivers in India, known as the Peninsular rivers. These rivers originate from the Peninsular plateau in southern India and are quite different in nature from the Himalayan rivers.
The Peninsular region is geologically very old and stable. It is composed of hard rocks and has a more uniform relief compared to the Himalayas. Because of this stability, the rivers flowing through this region follow more fixed and predictable courses.
This basic difference in geological structure is the main reason why Peninsular rivers differ so much from Himalayan rivers in their behavior and characteristics.
Nature of Peninsular Rivers
The most important feature of Peninsular rivers is that they are mainly dependent on rainfall. This means that their water flow is directly influenced by the monsoon.
During the rainy season, these rivers carry a large amount of water. However, during the dry season, their water level decreases significantly. Because of this seasonal variation, these rivers are often referred to as seasonal rivers.
Unlike Himalayan rivers, they do not receive water from glaciers. Therefore, they do not have a continuous supply of water throughout the year.
Another important characteristic is that these rivers have a relatively shorter length and a slower flow. Since they flow over hard rocky surfaces, the process of erosion is limited, and they do not form deep valleys like Himalayan rivers.
Direction of Flow and Water Divide
In Peninsular India, the Western Ghats act as a major water divide. This mountain range runs parallel to the western coast and plays a key role in determining the direction of river flow.
Most of the rivers originate from the Western Ghats and flow towards the east. This is because the general slope of the Peninsular plateau is towards the east. As a result, these rivers drain into the Bay of Bengal.
However, there are a few exceptions. Some rivers flow westward and drain into the Arabian Sea. These rivers are fewer in number but have distinct characteristics.
The Narmada River System
The Narmada River is one of the most important west-flowing rivers of Peninsular India. It originates near the Amarkantak hills in Madhya Pradesh.
What makes the Narmada unique is that it flows through a rift valley. A rift valley is formed due to the sinking of land between two parallel faults. This gives the river a straight and well-defined course.
As the Narmada flows westward, it passes through a narrow valley bordered by highlands. Near Jabalpur, it flows through marble rocks and forms deep gorges and waterfalls, including the famous Dhuandhar Falls.
The tributaries of the Narmada are relatively short and join the main river at almost right angles. Finally, the river empties into the Arabian Sea.
The Tapi River System
The Tapi River is another important west-flowing river. It originates in the Satpura ranges in Madhya Pradesh and flows parallel to the Narmada.
Like the Narmada, the Tapi also flows through a rift valley. However, it is shorter in length compared to the Narmada.
The Tapi flows through Madhya Pradesh, Maharashtra, and Gujarat before emptying into the Arabian Sea. Its course and structure closely resemble that of the Narmada, which is why both rivers are often studied together.
The Godavari River System
The Godavari is the largest Peninsular river. It originates from the Western Ghats near Nashik in Maharashtra.
From its source, it flows eastward across the Deccan plateau and covers a long distance before draining into the Bay of Bengal. Its length is about 1500 kilometers, making it the longest river in Peninsular India.
The drainage basin of the Godavari is very large and extends across several states, including Maharashtra, Madhya Pradesh, Odisha, and Andhra Pradesh.
Many tributaries join the Godavari, such as the Purna, Wardha, Pranhita, Manjra, Wainganga, and Penganga. These tributaries contribute significantly to its volume.
Due to its large size and importance, the Godavari is often referred to as the “Ganga of the South.”
The Mahanadi River System
The Mahanadi River originates in the highlands of Chhattisgarh. It flows eastward through Odisha and finally drains into the Bay of Bengal.
The river has a total length of about 860 kilometers and drains a large area covering parts of Maharashtra, Chhattisgarh, Jharkhand, and Odisha.
At its mouth, the Mahanadi forms a delta, which is fertile and suitable for agriculture. Like other east-flowing rivers, it carries sediments that contribute to delta formation.
The Krishna River System
The Krishna River originates near Mahabaleshwar in the Western Ghats of Maharashtra. It flows eastward across the Peninsular plateau and finally drains into the Bay of Bengal.
The river is about 1400 kilometers long and has a large drainage basin that covers Maharashtra, Karnataka, and Andhra Pradesh.
Several tributaries join the Krishna, including the Tungabhadra, Koyna, Ghataprabha, Musi, and Bhima. These tributaries play an important role in increasing the river’s water volume.
The Krishna basin is an important agricultural region and supports a large population.
The Kaveri River System
The Kaveri River is one of the most important rivers of southern India. It originates from the Brahmagiri hills in the Western Ghats.
The river flows through Karnataka and Tamil Nadu before emptying into the Bay of Bengal. Its length is about 760 kilometers.
Several tributaries such as the Amravati, Bhavani, Hemavati, and Kabini join the Kaveri.
The river also forms waterfalls and is used for hydroelectric power generation. Its waters are crucial for irrigation in southern India.
East-Flowing Smaller Rivers
In addition to the major rivers, there are several smaller rivers that flow towards the east. These include the Damodar, Brahmani, Baitarni, and Subarnarekha.
Although smaller in size, these rivers are important for the regions they flow through. They contribute to local agriculture and water supply.
Overall Understanding of Peninsular Rivers
When we look at Peninsular rivers as a whole, it becomes clear that they are different from Himalayan rivers in many ways. They are shorter, depend mainly on rainfall, and have a more stable course.
However, their importance is equally significant. They provide water for irrigation, support agriculture, and are essential for the livelihood of people in southern India.
These rivers form the backbone of the Peninsular region just as the Himalayan rivers do for northern India.
Introduction to Lakes
After studying rivers in detail, it is important to understand lakes, which are another significant component of the drainage system. Lakes act as natural reservoirs of water and play an important role in maintaining the balance of the environment.
A lake is a body of water that collects in a depression or hollow on the Earth’s surface. The water in a lake may be permanent or seasonal, depending on the climatic conditions and the source of water.
In India, lakes vary widely in size, origin, and characteristics. Some lakes contain fresh water, while others are saline. Some exist throughout the year, while others appear only during the rainy season.
Formation of Lakes
Lakes are formed due to a variety of natural and human processes. In mountainous regions, especially in the Himalayas, many lakes are formed by glacial action. When glaciers move, they erode the land and create depressions. After the glaciers melt, these depressions get filled with water and form lakes.
Some lakes are formed by the action of rivers. When a river changes its course, parts of its old channel may get cut off, forming crescent-shaped lakes. These are often found in floodplains.
In coastal areas, lakes can be formed when sandbars or spits block the movement of seawater, trapping water in a lagoon-like formation. Examples of such lakes include Chilika, Pulicat, and Kolleru.
There are also lakes formed due to human activities. When dams are built across rivers, water accumulates behind them, forming artificial lakes or reservoirs.
Major Lakes of India
India has many important lakes, each with its own characteristics.
In the Kashmir Valley, lakes such as Wular and Dal are well known. Wular Lake is the largest freshwater lake in India. These lakes are not only important for water storage but also attract tourists from different parts of the country.
Sambhar Lake in Rajasthan is an example of a saltwater lake. It is used for the production of salt and plays an economic role in the region.
In coastal areas, Chilika Lake is one of the largest lagoons in India. Similarly, Pulicat Lake and Kolleru Lake are important coastal lakes formed due to depositional activities.
In northeastern India, Loktak Lake is another significant lake known for its unique floating vegetation.
Importance of Lakes
Lakes are extremely important for both natural ecosystems and human life. One of their key functions is to regulate the flow of rivers. During periods of heavy rainfall, lakes help in storing excess water and reducing the risk of floods. During dry seasons, they release water gradually, helping maintain a steady flow.
Lakes also influence the climate of the surrounding areas. They help in maintaining humidity and temperature balance, making the environment more stable.
They support a rich variety of aquatic life and maintain ecological balance. In addition, lakes are important for tourism and recreation, attracting visitors and contributing to local economies.
Artificial lakes and reservoirs are also used for generating hydroelectric power, which is an important source of energy.
Economic Importance of Rivers
Rivers have played a vital role in human history. Most ancient civilizations developed along river banks because rivers provided water, fertile soil, and means of transport.
In India, where a large portion of the population depends on agriculture, rivers are extremely important. They provide water for irrigation, which is essential for crop production.
Rivers are also a major source of drinking water for both rural and urban populations. Without rivers, meeting the daily water needs of people would be extremely difficult.
Another important use of rivers is in the generation of hydroelectric power. By constructing dams, the energy of flowing water is converted into electricity, which supports industries and households.
In some regions, rivers are also used for transportation. Boats and ships carry goods and people, making rivers an important means of communication.
Problem of River Pollution
In modern times, river pollution has become a serious concern. With increasing population, industrialization, and urbanization, the quality of river water has been severely affected.
Domestic waste, industrial effluents, and agricultural chemicals often flow into rivers, polluting the water. This not only affects human health but also harms aquatic life.
Earlier, rivers had the natural ability to clean themselves through continuous flow. However, with increasing pollution, this self-cleaning capacity is gradually declining.
As a result, many rivers are becoming unsuitable for drinking and even for agricultural use in some areas.
Efforts for River Conservation
To address the problem of river pollution, several initiatives have been taken. One of the earliest efforts was the Ganga Action Plan launched in 1985. Its aim was to reduce pollution and improve the water quality of the Ganga.
Later, the National River Conservation Plan was introduced to include other rivers as well. These programs focus on reducing pollution levels and maintaining the quality of river water.
Despite these efforts, river conservation remains a major challenge. It requires not only government action but also public awareness and participation.
People need to understand the importance of clean water and take responsibility for protecting rivers.
Overall Conclusion
When we look at the entire chapter, it becomes clear that the drainage system of India is not just a geographical feature but the foundation of life, economy, and environment.
The Himalayan rivers, with their perennial flow, support vast fertile plains and large populations. The Peninsular rivers, though seasonal, are equally important for the southern part of the country.
Lakes complement this system by storing water, regulating flow, and maintaining ecological balance.
However, with increasing pollution and overuse, these water resources are under threat. If proper steps are not taken, water scarcity may become a serious issue in the future.
Therefore, it is essential to conserve water, reduce pollution, and use these resources wisely. Protecting rivers and lakes is not just the responsibility of the government but of every individual.
Frequently Asked Questions (FAQs)
What is drainage?
Drainage refers to the system through which water flows across the land surface and finally reaches seas, lakes, or oceans through rivers.
What is a drainage basin?
A drainage basin is the area of land from which a river and its tributaries collect water.
What is a water divide?
A water divide is an elevated landform such as a hill or mountain that separates two drainage basins.
Why are Himalayan rivers perennial?
Himalayan rivers are perennial because they receive water from both rainfall and melting snow from the mountains.
Where does the Ganga originate?
The Ganga originates from the Gangotri Glacier as the Bhagirathi and becomes the Ganga after meeting the Alaknanda at Devprayag.
Which is the largest Peninsular river in India?
The Godavari is the largest Peninsular river in India and is often called the "Ganga of the South."
What is the Sundarban Delta?
The Sundarban Delta is the world's largest delta formed by the Ganga and Brahmaputra rivers.
How are lakes formed?
Lakes are formed by natural processes such as glacial action, river changes, and coastal deposition, as well as by human activities like dam construction.
What is the economic importance of rivers?
Rivers are important for irrigation, drinking water supply, hydroelectric power generation, and transportation.
What are the main causes of river pollution?
The main causes of river pollution include domestic waste, industrial discharge, and agricultural chemicals.