Hydrosphere Archives

1. With reference to the water on the planet Earth, consider the followin

With reference to the water on the planet Earth, consider the following statements :

1. The amount of water in the rivers and lakes is more than the amount of groundwater.
2. The amount of water in polar ice caps and glaciers is more than the amount of groundwater.

Which of the statements given above is/are correct?

1 only

2 only

Both 1 and 2

Neither 1 nor 2

This question was previously asked in

UPSC IAS – 2021

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The correct answer is B) 2 only.

– Statement 1 is incorrect. The amount of groundwater on Earth is significantly greater than the amount of water in all rivers and lakes combined. Approximately 30% of the world’s freshwater is groundwater, while surface water bodies like rivers and lakes hold a much smaller fraction (less than 1%).
– Statement 2 is correct. The largest reservoir of freshwater is in polar ice caps and glaciers, which hold approximately 68.7% of the total freshwater. This amount is greater than the groundwater reservoir, which holds about 30.1% of freshwater.

– The vast majority (around 97.3%) of Earth’s water is saline water in oceans. Freshwater accounts for only about 2.7%, most of which is locked up in ice and groundwater.

2. On the planet earth, most of the freshwater exists as ice caps and gla

On the planet earth, most of the freshwater exists as ice caps and glaciers. Out of the remaining freshwater, the largest proportion

is found in atmosphere as moisture and clouds

is found in freshwater lakes and rivers

exists as groundwater

exists as soil moisture

This question was previously asked in

UPSC IAS – 2013

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The correct option is C, stating that out of the remaining freshwater (after ice caps and glaciers), the largest proportion exists as groundwater.

– Approximately 68.7% of the Earth’s freshwater is stored in ice caps, glaciers, and permanent snow.
– The remaining freshwater (about 31.3%) is primarily found underground as groundwater (about 30.1%).
– A much smaller amount of freshwater exists on the surface (lakes, rivers, swamps, about 1.2%) and in the atmosphere (moisture and clouds, a very small percentage) and as soil moisture (also a small percentage, part of the surface/other category).
– Specifically, groundwater accounts for the vast majority of available liquid freshwater on Earth.

Although surface water in lakes and rivers is the most visible form of freshwater and the easiest to access, it constitutes only a tiny fraction of the total freshwater resources. Groundwater is a crucial source for drinking water and irrigation globally.

3. The distance between two successive crests or troughs of sea waves is

The distance between two successive crests or troughs of sea waves is called as

Wavelength

Wave height

Wave frequency

Fetch

This question was previously asked in

UPSC CAPF – 2020

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The correct option is A. The distance between two successive crests or troughs of a wave is defined as its wavelength.

– Wavelength is the horizontal distance between corresponding points on consecutive waves, such as from crest to crest or trough to trough.
– Wave height is the vertical distance between the crest (highest point) and the trough (lowest point) of a wave.
– Wave frequency is the number of complete wave cycles (or crests/troughs) that pass a fixed point in a given unit of time.
– Fetch is the distance over water that the wind has blown in a consistent direction and speed, influencing the size of the waves generated.

These terms are fundamental properties used to describe waves, including ocean waves. Understanding these characteristics is important in oceanography, coastal engineering, and navigation.

4. Which of the following statements with regard to the continental shelf

Which of the following statements with regard to the continental shelf is NOT correct ?

Shelves are absent close to plate boundaries

They are highly sedimented

They have abrupt falls towards the continental slopes

They are rich fishing areas

This question was previously asked in

UPSC CAPF – 2015

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The statement that is NOT correct with regard to the continental shelf is “Shelves are absent close to plate boundaries”.

– Continental shelves are the extended perimeter of each continent, associated with relatively shallow water compared to the open ocean.
– Statement B is correct: Continental shelves receive large amounts of sediment from rivers and coastal erosion, making them highly sedimented environments.
– Statement C is correct: The continental shelf ends at the shelf break, where there is a relatively abrupt increase in slope leading down to the continental slope and then the abyssal plain.
– Statement D is correct: Due to shallow waters, sunlight penetration, and nutrient-rich upwellings, continental shelves are highly productive ecosystems supporting abundant marine life, making them important fishing areas.
– Statement A is incorrect: While continental shelves are often narrower or even largely absent at active plate boundaries (like convergent or transform margins, e.g., along the west coast of South America or parts of California) compared to passive margins (e.g., along the east coast of North America), they are not universally absent at all plate boundaries. Some types of plate boundaries or specific locations on active margins can still have continental shelves, although perhaps limited in width. Saying they are “absent” is too strong a generalization and therefore incorrect.

Passive continental margins are created by rifting and continental breakup, leading to wide, stable shelves. Active continental margins, associated with plate boundaries, are tectonically active and can have narrow or non-existent shelves depending on the specific geological processes occurring (like subduction, collision, or transform faulting).

5. What happens to the water depth as the Tsunami waves approach the coas

What happens to the water depth as the Tsunami waves approach the coast ?

Decreases

Increases

Increases and decreases alternatively

Neither increases nor decreases

This question was previously asked in

UPSC CAPF – 2009

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As Tsunami waves approach the coast, the water depth decreases.

Tsunami waves are long-period waves. As they move from the deep ocean into shallower coastal waters, their speed decreases due to friction with the seabed, but their height increases significantly due to the conservation of energy. This phenomenon is known as shoaling.

In the deep ocean, tsunamis have a long wavelength and small amplitude (height), making them often unnoticed by ships. As they enter shallow water, the wavelength shortens, the speed slows dramatically, and the wave height can build up to several meters or even tens of meters upon reaching the coast.

6. The major portion of the Great Artesian Basin in Australia is located

The major portion of the Great Artesian Basin in Australia is located in

Western Australia

Victoria

Queensland

Northern Territory

This question was previously asked in

UPSC NDA-2 – 2022

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The Great Artesian Basin is a vast and deep groundwater basin in Australia. It underlies about 22% of the continent, including most of Queensland, the north-eastern part of South Australia, the south-eastern part of the Northern Territory, and the north-western part of New South Wales.

While the basin spans across several states and territories, the largest portion by area is located within the state of Queensland.

The Great Artesian Basin is the largest and deepest artesian basin in the world. It is a crucial water source for arid and semi-arid inland areas of Australia, supporting pastoral activities, mining, and communities. Artesian groundwater is water that rises to the surface under its own pressure.

7. Which one of the following factors does not affect the distribution of

Which one of the following factors does not affect the distribution of groundwater ?

Amount of precipitation

Rate of evaporation

Ability of the ground surface to allow water to infiltrate into the groundwater system

Distance from the sea

This question was previously asked in

UPSC NDA-2 – 2021

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Distance from the sea is the factor among the given options that does not universally affect the distribution of groundwater.

Groundwater distribution is primarily controlled by factors related to the supply of water and the ability of the ground to store and transmit it. These include the amount of precipitation (recharge), the rate of evaporation (loss and reduced recharge), and the geological characteristics (porosity, permeability, infiltration capacity). Distance from the sea is relevant mainly for coastal hydrogeology (e.g., saltwater intrusion) but is not a fundamental factor governing groundwater distribution in all landscapes, particularly inland areas.

Precipitation is the main source of groundwater recharge. High evaporation rates reduce surface water and soil moisture, limiting infiltration. The ability of the ground surface (and underlying strata) to allow infiltration and hold water determines where groundwater can accumulate and how it is distributed in aquifers. While distance from the sea influences specific conditions like salinity gradients and tidal effects in coastal aquifers, it doesn’t determine the general presence or absence and distribution of groundwater in non-coastal regions, which are governed by climatic and geological factors.

8. The process through which groundwater is brought up to the surface is

The process through which groundwater is brought up to the surface is called

eluviation

illuviation

capillary action

desilication

This question was previously asked in

UPSC Geoscientist – 2022

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Capillary action is the phenomenon where a liquid moves up through a narrow space against the force of gravity. In the context of soil, this occurs because water molecules are attracted to soil particles (adhesion) and to each other (cohesion). These forces, combined with surface tension, draw water upwards through the pore spaces in the soil from the water table below, bringing groundwater closer to or onto the surface (known as capillary rise).

– Capillary action allows water to move upwards in narrow tubes or porous materials.
– It is a key mechanism for the upward movement of groundwater in soil.
– Adhesion, cohesion, and surface tension are the forces involved.

Eluviation and illuviation are processes related to the movement and accumulation of soil materials within different soil horizons, primarily driven by percolating water moving downwards. Desilication is a weathering process that removes silica from minerals, common in tropical climates but not the process that brings groundwater to the surface.

9. The edge effect at the contact of continental fresh water and sea wate

The edge effect at the contact of continental fresh water and sea water results in:

non-deposition of sediments due to turbulence.

deposition of sand due to fall in system energy.

deposition of organic matter due to density difference.

flocculation of clays resulting in formation of mud deposits.

This question was previously asked in

UPSC Geoscientist – 2020

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When freshwater mixes with saltwater, especially in estuaries, the dissolved salts (ions) in the saltwater neutralize the negative charges on clay particles carried by the freshwater. This neutralization reduces the electrostatic repulsion between clay particles, causing them to clump together (flocculate) and settle out of suspension, forming mud deposits.

Flocculation of clay particles is a key process occurring at the salt-freshwater interface in estuaries, driven by changes in salinity.

This flocculation and subsequent deposition of fine sediments are major factors contributing to the formation of muddy bottoms, tidal flats, and salt marshes characteristic of estuarine environments. The mixing zone, where this occurs, is often referred to as the “turbidity maximum.”

10. Which one of the following is the cause of long-term sea-level change?

Which one of the following is the cause of long-term sea-level change?

Atmospheric disturbance

Change in marine water density

Melting of icebergs

Melting of ice sheets

This question was previously asked in

UPSC CDS-1 – 2016

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The correct answer is the melting of ice sheets.

Long-term sea-level change is primarily driven by factors that significantly alter the total volume of water in the oceans or the size of the ocean basins over geological timescales. Melting of large ice sheets (like Greenland and Antarctic ice sheets) adds substantial mass of water to the ocean, directly contributing to long-term sea-level rise. Thermal expansion of seawater due to warming is another significant long-term factor.

Atmospheric disturbances cause short-term, localized changes in sea level (storm surges). Changes in marine water density can contribute to steric sea-level change (thermal expansion or contraction), which is a long-term factor, but melting of ice sheets represents a direct mass addition. Melting of floating icebergs does not significantly alter sea level, as the ice displaces a volume of water equal to its mass (Archimedes’ principle).