Class 11 Geography (India: Physical Environment) Chapter 3 Drainage System

Key Concept: Watershed vs. Basin

b) Watershed

[Solution Description] A watershed, also known as a drainage divide or ridge, is the geographical feature that marks the boundary between two different drainage basins. It represents a high point or ridge that directs water flow into separate drainage systems.

Key Concept: Basic Identification

d) They become dry during some parts of the year

[Solution Description] Non-perennial rivers are characterized by carrying water only during certain periods, such as the rainy season, due to their dependence on seasonal rainfall. They do not flow permanently throughout the year like perennial rivers.

Key Concept: Rainfall Impact

b) Rainfall during both southwest and northeast monsoon seasons

[Solution Description] The Kaveri River experiences rainfall during both the southwest monsoon in the upper catchment area and the northeast monsoon in the lower part. This dual monsoon influence ensures a perennial flow of water in the river.

Key Concept: Geological Impact, River Course Dynamics

b) It leads to formation of deep gorges and increases sediment load.

[Solution Description] The uplift of the Himalayan region has a significant impact on river systems such as the Ganga and Brahmaputra by causing them to form deep gorges due to the steep gradient. Additionally, this process generates increased sediment load because of erosion in the elevated areas. In plains, the rivers can meander and shift courses due to this sediment deposition.

Key Concept: Geological Events

c) Slight tilting of the Peninsular block

[Solution Description] The fixed courses and absence of meanders in the Peninsular rivers are mainly due to the stability of their course, which is attributed to the peninsular block’s slight tilting. This geophysical change ensured that many rivers had set paths without much deviation or formation of meanders.

Key Concept: River Basin Comparison

d) Narmada

[Solution Description]

The Tapi River is a westward flowing river as it flows towards the Arabian Sea and is part of the Peninsular drainage system, which means it does not form any large deltas. Rivers similar in direction with such characteristics are rare but the Narmada River also shares these attributes, being a westward-flowing river through a rift valley.

Key Concept: Historical Evolution

d) Pleistocene

[Solution Description] The Pleistocene epoch was characterized by significant climatic changes that contributed to the dismemberment of the Indo-Brahma river, resulting in the formation of separate river systems like the Ganga and Brahmaputra.

Key Concept: Drainage System Comparison

a) Himalayan rivers are perennial

[Solution Description] The Peninsular rivers have fixed courses due to the stable geological structure, while the Himalayan rivers often change their courses due to tectonic activity and sedimentation.

Key Concept: River Confluence

b) Sonpur

[Solution Description] As per the information in the syllabus, the Gandak river joins the Ganga at Sonpur. Thus, Sonpur is the correct location among the provided options where Gandak meets Ganga.

Key Concept: River Confluence

c) Near Arrah, west of Patna

[Solution Description] The Son river joins the Ganga near Arrah, which is located west of Patna. According to geographical data, this is the confluence point of these two rivers.

Key Concept: Coastal Region Rivers

c) Periyar

[Solution Description] The Periyar River is known to be part of the western coastal region stretching from the Konkan to the Malabar coast.

Key Concept: River Identification

d) Ganga

[Solution Description] A perennial river is one that has continuous flow throughout the year, sourced by melting snow or consistent rainfall. The Ganga is a perennial river due to its origin from the Himalayas where it gets fed by melting glaciers.

Key Concept: Drainage Patterns Examples

b) Radial

[Solution Description] A radial drainage pattern occurs when streams flow away from a central high area, like a dome or volcanic cone. The pattern resembles the spokes of a wheel and is typical in areas with conical hills.

Key Concept: River Basin Size

d) Krishna

[Solution Description] The Krishna River is one of the major rivers in India, and its catchment area is larger than 20,000 sq. km. Other options are smaller river basins.

Key Concept: Pattern Characteristics

b) Resembling tree branches with irregular tributary entry

[Solution Description] Dendritic drainage patterns are characterized by their resemblance to tree branches, where tributaries enter the main river at various angles.

Key Concept: Historical Changes

d) Pleistocene Upheaval

[Solution Description] The dismemberment of the Indo-Brahma river was significantly influenced by the Pleistocene upheaval in the western Himalayas. This event caused shifts in geological formations, leading to the realignment and division of the original river system into separate drainage systems.

Key Concept: Drainage Patterns

c) Dendritic

[Solution Description] A dendritic drainage pattern resembles the branching pattern of tree roots due to the random merging of streams with no obvious structural control.

Key Concept: Example Identification

c) Rivers originating from the Amarkantak Range

[Solution Description] The rivers originating from the Amarkantak Range are known for their radial drainage pattern, where they start from a central highland and flow outwards.

Key Concept: Tributary Meeting Points

d) Devprayag

[Solution Description] The Bhagirathi and Alaknanda rivers confluence at Devprayag, which is a well-known point of their meeting to collectively form the river Ganga. Devprayag is a significant pilgrimage site in Uttarakhand.

Key Concept: Comparative Length

c) Godavari River is longer

[Solution Description] Among the options given, the Godavari River is longer than the Mahanadi River. The Mahanadi is 851 km long, while the Godavari extends over approximately 1465 km, making it the longest river in the list provided.

Key Concept: River Orientation

b) Bay of Bengal

[Solution Description] Most Indian rivers discharge their waters into the Bay of Bengal. The eastern side of India has more major river systems, such as the Ganges and Brahmaputra, which flow into this large bay.

Key Concept: Cultural Significance

d) Ganga

[Solution Description] The Ganga river holds immense cultural significance in India. It is considered sacred and is central to numerous religious ceremonies and rituals, making it a vital part of Indian culture.

Key Concept: Basin Coverage

c) 31%

[Solution Description] The distribution of the Godavari River’s basin is given as 49% in Maharashtra, and 20% in Madhya Pradesh and Chhattisgarh combined. Hence, the percentage of the basin lying outside these states would be $100% – (49% + 20%) = 31%$.

Key Concept: Major River Basins

b) Ganga

[Solution Description] Major river basins are those with extensive catchment areas. The Ganga Basin is one of the largest river basins in India, covering significantly more than 20,000 sq. km of catchment area, while Kalindi, and Meghna are not considered major basins as per this criterion.

Key Concept: Tributary Confluence

d) Near Sarai Sidhu in Pakistan

[Solution Description] The Ravi River joins the Chenab River near a place called Sarai Sidhu in Punjab, Pakistan.

Key Concept: River Characteristics

d) Perennial flow

[Solution Description] Himalayan rivers are known for their perennial flow, meaning they carry water throughout the year due to constant glacial melt and rainfall across the region.

Key Concept: Drainage System Classification

c) Trellis

[Solution Description] A trellis drainage pattern forms in regions with alternating bands of resistant and less resistant rock, often following structural lines such as ridges and valleys. The main stream runs parallel to the ridges, while tributaries intersect at right angles.

Key Concept: Tributary Identification

d) Mandakini

[Solution Description] The Alaknanda river is fed by several tributaries. Among the options provided, Mandakini is a known tributary of the Alaknanda, joining it in Rudraprayag.

Key Concept: Name in Tibet

b) Singi Khamban

[Solution Description] In Tibet, the Indus River is referred to as ‘Singi Khamban’ or Lion’s mouth according to the given syllabus.

Key Concept: Geological Events

d) Tilting of Peninsular block

[Solution Description] The tilting of the Peninsular block is a key geological event that has resulted in many rivers flowing eastward toward the Bay of Bengal. This structural tilt allowed the formation of the current river courses.

Key Concept: Tributary Flow

b) West of the Rohtang Pass

[Solution Description] The Ravi River originates west of the Rohtang Pass in the Kullu hills, and then it flows through the Chamba Valley in Himachal Pradesh.

Key Concept: Tributary Characteristics

c) Subansiri

[Solution Description] The Subansiri river is known as an antecedent river.

Key Concept: River System Classification

d) Sutlej

[Solution Description] The Indus River system originates in the Tibetan Plateau and flows through Kashmir, India, and Pakistan. Key tributaries include Jhelum, Chenab, Ravi, Beas, and Sutlej. Among the given options, Sutlej is a prominent river that is part of the Indus River system.

Key Concept: River Impact, Historical River Changes

c) Regular destruction of villages and towns due to unexpected flooding events.

[Solution Description] The Kosi River is notorious for its unpredictable course changes due to sediment deposition in the plains, often leading to flooding and altering human settlement patterns. Such changes have historically affected the infrastructure, requiring adaptive measures by local populations to manage the floods and their consequences.

Key Concept: River Identification

c) The Ganga

[Solution Description] A perennial river carries water throughout the year irrespective of the season. In India, the Ganga is a well-known perennial river as it is fed by melting snow and glaciers from the Himalayas along with rainfall.

Key Concept: River Characteristics

b) Turbulent and dynamic

[Solution Description] The Brahmaputra, known as Tsangpo in Tibet, is characterized by its turbulent and dynamic nature as it descends from the Tibetan plateau.

Key Concept: River Behavior

c) Due to sediment deposition blocking its course

[Solution Description] The Kosi river carries large amounts of sediments from the Himalayan region, and this sediment deposition can block parts of the river’s path, causing it to shift its course.

Key Concept: Drainage Pattern

d) Dendritic

[Solution Description] Dendritic drainage patterns are most commonly found in areas with uniform material where non-perennial rivers generally occur, unlike radial or trellis patterns which are formed under different geological conditions.

Key Concept: Drainage Orientation

b) Ganga

[Solution Description] The Ganga River is one of the major rivers in India that flows eastward and discharges into the Bay of Bengal.

Key Concept: River Flow Characteristics

c) Godavari

[Solution Description] Many Peninsular rivers are characterized by their non-perennial nature due to the seasonal rainfall they depend upon. The Godavari River, despite being significant, exhibits a non-perennial flow characteristic, typical of several Peninsular rivers.

Key Concept: Real-world Example

b) Folded mountain regions

[Solution Description] Trellis drainage patterns are often found in folded mountain regions due to their geological structure.

Key Concept: Hydrological Challenges, River Management Strategies

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description] The assertion states that the Krishna River’s non-perennial nature contributes to water scarcity during dry periods. This is accurate because a non-perennial river does not maintain flow year-round, leading to reduced water availability when rainfall is low. The reason suggests that efficient management and storage solutions are implemented to counteract these fluctuations. However, the persistent issues of water scarcity indicate that while measures may be attempted, they have not been entirely successful or sufficient. Hence, both statements are true but the Reason does not correctly explain the Assertion since actual mitigation has not completely addressed the problem.

Key Concept: Comparative Analysis

b) Uplift of the Potwar Plateau

[Solution Description] The event that caused the separation of these river systems was due to the uplift of a significant geological structure, which became a prominent feature acting as a divide. The Potwar Plateau is known for such an uplift during the Pleistocene epoch.

Key Concept: River Name Recognition

c) Brahmaputra

[Solution Description] When the Dibang and Lohit Rivers merge with it, the river continues as the Brahmaputra.

Key Concept: River Characteristics

c) They flow through rift valleys

[Solution Description] Both the Narmada and Tapi rivers flow through rift valleys, which makes them unique among the west-flowing rivers of peninsular India. This geological feature prevents the formation of alluvial deposits typically found in other river systems.

Key Concept: River Origin

d) Tibet

[Solution Description] The Subansiri river is an antecedent river that originates in Tibet. This is a basic fact regarding the origin of the Subansiri.

Key Concept: River Tributaries

c) Bhima

[Solution Description] The Krishna river has several tributaries, including the Tunga, Bhadra, and Bhima. Among the options given, the correct answer is the Bhima river.

Key Concept: River Course

d) Jamuna

[Solution Description] When the Brahmaputra River flows into Bangladesh, it is called the Jamuna. This name change signifies its geographical transition as it becomes part of the river system that joins with the Padma River before flowing into the Bay of Bengal.

Key Concept: Complex Processes, Integrated Concepts

c) Steep gradients and resistant rock facilitate vertical erosion.

[Solution Description]

The formation of V-shaped valleys is influenced by several factors including rock resistance and gradient. In the Himalayas, these valleys are typically formed where resistant rocks are subjected to the erosional force of rivers descending from steep gradients. Due to the high flow velocity over hard rock substrates, vertical erosion predominates, leading to the characteristic V-shape. The combination of steep slopes and hard rocks contributes to intensified downcutting, making V-shaped valleys more pronounced.

Key Concept: River Identification

c) Kalindi

[Solution Description] Minor river basins are defined as those having a catchment area smaller than 2,000 square kilometers. Among the listed options, the correct answer should be a river known for fitting this criterion.

Key Concept: Scheme Identification

c) Periyar Diversion Scheme

[Solution Description] The Periyar Diversion Scheme is listed as a specific example of an inter-basin water transfer scheme in the syllabus. Options like Yamuna Action Plan, Namami Devi Narmade, and Ganga Action Plan do not fit into this category.

Key Concept: Geological Events Sequence

a) Upheaval of the Himalayas, Subsidence of the western flank, Slight tilting

[Solution Description] The geological history of the Peninsular region involves the upheaval of the Himalayas, which led to subsidence and trough faulting, influencing river characteristics. Following this, there was a subsidence of the western flank during the early tertiary period. Lastly, slight tilting occurred, orienting the drainage towards the Bay of Bengal.

Key Concept: Watershed vs Basin

a) River basins are larger than watersheds

[Solution Description] A watershed is generally smaller than a river basin and refers to the land area that channels rainfall to creeks, streams, and rivers, eventually reaching outflows like reservoirs, bays, and the ocean. Hence, watersheds are smaller compared to river basins.

Key Concept: River Direction

c) West to East

[Solution Description] Most of the major Peninsular rivers in India, such as Godavari, Mahanadi, Krishna, and Kaveri, typically flow from west to east, discharging into the Bay of Bengal.

Key Concept: Drainage Orientation

c) Bay of Bengal

[Solution Description] Medium river basins in India mostly orient their drainage towards the Bay of Bengal or Arabian Sea based on their location.

Key Concept: Evolution Process

c) Miocene

[Solution Description] The Indo-Brahma river is believed to have existed before undergoing major transformations due to geological events. The Miocene-Pliocene transition marked a time of significant tectonic activity, resulting in the alteration of river systems, including the dismemberment of the Indo-Brahma river into the Indus, Ganga, and Brahmaputra systems.

Key Concept: River Origin

b) Tibetan region

[Solution Description] The Indus River originates in the Tibetan region near Lake Mansarovar. This is a well-known fact about its origin.

Key Concept: Drainage Patterns

a) Radial

[Solution Description] A radial drainage pattern occurs when streams radiate outwards from a central high point, resembling the spokes of a wheel or a fan.

Key Concept: River Orientation Causes

b) Southeastward tilting of the Peninsular block

[Solution Description]

The orientation of most Peninsular rivers towards the Bay of Bengal is attributed to the southeast tilting of the Peninsular block. Due to this tilt, rivers naturally follow the gradient from west to east.

Key Concept: River Name Change

d) Jamuna

[Solution Description] As the Brahmaputra River enters Bangladesh near Dhubri, it is joined by the Tista river and is known as the Jamuna.

Key Concept: River Source Identification

c) Himalayas

[Solution Description] The Brahmaputra river originates in the Himalayas, specifically from the Angsi Glacier located in Tibet.

Key Concept: Geological Feature

c) Rift Valley

[Solution Description] The Narmada River flows through a rift valley, which is a distinctive geographical feature formed due to tectonic forces causing subsidence and faulting. This unique path lies between the Satpura range in the south and the Vindhyan range in the north.

Key Concept: Meeting Point

b) Govindgarh

[Solution Description] The Saraswati and Sabarmati branches of the Luni River meet at Govindgarh.

Key Concept: Simple Classification

c) Narmada

[Solution Description] The Narmada River discharges into the Arabian Sea. It flows westward through central India and empties into the Arabian Sea, making it distinct from rivers like the Ganga and Brahmaputra that discharge into the Bay of Bengal.

Key Concept: River System

c) Indus

[Solution Description] The Jhelum river originates from Verinag and ultimately joins the Chenab river near Jhang in Pakistan, making it a part of the Indus River system.

Key Concept: Flood Causes

b) Heavy rainfall

[Solution Description] According to the syllabus, heavy rainfall is listed as one of the causes of floods. It leads to an increased volume of water, which can overflow riverbanks.

Key Concept: Conceptual Understanding

a) Centripetal flows into a central point, radial flows outward

[Solution Description] In a centripetal pattern, drainage converges towards a centrally located depression, whereas in a radial pattern, streams radiate outward from a central elevated area.

Key Concept: Geological Impact

a) Subsidence of the western flank of the Peninsula

[Solution Description] The absence of meanders in Peninsular rivers such as the Narmada and Tapi is mainly due to the subsidence of the western flank of the Peninsula during the early tertiary period. This event led to a steep gradient, meaning the rivers flow more directly rather than winding, which results in a fixed course with less opportunity for meandering.