Grade-7 Science, Scarcity of Water

 Scarcity of Water

 

Answer Orally

1. Give two reasons for the scarcity of water.

Ans- Two reasons for the scarcity of water are increasing population and overuse of water resources due to industrialization and agricultural activities.

2. Define infiltration.

Ans- Infiltration refers to the process of seepage or penetration of water into the soil or porous rock layers.

3. How is water present in aquifers pumped out?

Ans- Water present in aquifers is pumped out using wells, boreholes, or tube wells by applying pressure to push the water to the surface.

4. Give two ways by which you can conserve water.

Ans- Two ways to conserve water are fixing leaks in pipes and taps and practicing rainwater harvesting.

5. Name three different states of water.

Ans- The three different states of water are solid (ice), liquid (water), and gas (water vapor/steam).

6. Define water cycle,

Ans- The water cycle is the continuous movement of water on, above, and below the Earth's surface through processes such as evaporation, condensation, precipitation, and runoff.

7. Why is the water present in seas and oceans saline?

Ans- The water present in seas and oceans is saline because it contains high levels of dissolved salts, which have accumulated over time through processes such as erosion and mineral leaching from rocks.

8. What is water table?

Ans- The water table is the level below the Earth's surface at which the ground is saturated with water. It represents the upper boundary of the zone of saturation where groundwater is present.

 

Mind Scrambler

Unscramble each of the following to form a word or term.

(a) NEVSORACTONI - CONSERVATION

(b) RUQIFAE – AQUIFER

 

Answer in Detail

1. In which all ways is water important to you?

Ans- Water is important to us in several ways:

• Water is essential for hydration and maintaining bodily functions.
• It facilitates digestion, absorption of nutrients, and transportation of substances within the body.
• Water is crucial for personal hygiene, cooking, and washing.
• It plays a vital role in agriculture for irrigation and plant growth.
• Water is used for generating electricity, industrial processes, and transportation.

 

2. Describe water cycle with the help of a diagram.

1.    Ans- The water cycle, also known as the hydrological cycle, describes the continuous movement of water on, above, and below the Earth's surface. Here's a brief description along with a diagram:

 

Diagram

The water cycle begins with evaporation, where water from oceans, lakes, rivers, and other water bodies is heated by the sun and transformed into water vapor, rising into the atmosphere. Condensation occurs as the water vapor cools, forming clouds. Precipitation happens when water droplets in clouds combine and fall to the Earth's surface as rain, snow, sleet, or hail. Surface runoff occurs as precipitation flows over the land surface, filling rivers, lakes, and other bodies of water. Some precipitation infiltrates the soil and becomes groundwater, replenishing aquifers. Eventually, water returns to the oceans through surface runoff and groundwater flow, completing the cycle.

 

3. Write a note on groundwater.

Ans- Groundwater refers to water that saturates the soil and fills the cracks and pores in underground formations of rocks and soil. Here are some key points about groundwater:

• It is a vital source of drinking water for many communities.
• Groundwater can be accessed through wells, boreholes, or springs.
• The level of groundwater, known as the water table, varies depending on factors such as precipitation and extraction rates.
• Groundwater recharge occurs when precipitation infiltrates the soil and replenishes underground aquifers.
• Overexploitation of groundwater can lead to depletion, causing the water table to drop and wells to run dry.

 

4. Nearly three-fourths of the earth is covered with water, yet there is an acute scarcity of water in many parts of the world. Give reasons.

Ans- Despite the Earth being covered with water, there is a scarcity of water in many parts of the world due to several reasons:

• Uneven distribution of freshwater resources, with some regions experiencing abundance while others face scarcity.
• Pollution and contamination of water sources, making them unfit for human consumption.
• Climate change leading to altered precipitation patterns, droughts, and water stress in certain areas.
• Overuse and mismanagement of water resources, including unsustainable agricultural practices, industrial activities, and urbanization.

 

5. How does increasing population lead to depletion of water table?

Ans- Increasing population leads to the depletion of the water table due to several factors:

• Rising demand for water for drinking, sanitation, agriculture, and industrial purposes.
• Urbanization and expansion of infrastructure leading to increased water consumption and reduced infiltration of rainwater into the ground.
• Higher rates of groundwater extraction for domestic and agricultural use, exceeding natural recharge rates and causing the water table to decline.

 

6. Agricultural activities lead to depletion of water table. Explain.

Ans- Agricultural activities contribute to the depletion of the water table through various means:

• Excessive irrigation practices, such as flood irrigation, result in water wastage and inefficient use of groundwater.
• Intensive farming methods requiring large amounts of water for crop cultivation.
• Expansion of agricultural land at the expense of natural habitats and water recharge areas, reducing infiltration and groundwater replenishment.

 

7. What is the role of deforestation in depletion of water table?

Ans- Deforestation plays a significant role in the depletion of the water table by:

• Removing vegetation cover that helps retain soil moisture and facilitates infiltration of rainwater into the ground.
• Accelerating soil erosion and sedimentation of rivers and streams, reducing water storage capacity and groundwater recharge.
• Disrupting ecological processes that regulate water flow, such as transpiration by trees and the water cycle.

 

8. Discuss the importance of water for plants.

Ans- Water is essential for plants for various reasons:

• It is a key component of photosynthesis, the process by which plants convert sunlight into energy and produce oxygen.
• Water transports nutrients and minerals from the soil to different parts of the plant, supporting growth and development.
• It helps regulate plant temperature through transpiration, where water evaporates from the leaves, cooling the plant and maintaining hydration.
• Adequate water availability is crucial for germination, flowering, fruiting, and overall plant health and productivity.

 

Answer Briefly

1. What are the three states of water?

Ans- The three states of water are solid (ice), liquid (water), and gas (water vapor/steam).

2. What are the different sources of water?

Ans- Different sources of water include rainwater, surface water (rivers, lakes, and streams), and groundwater.

3. Why is sea and ocean water unfit for human consumption?

Ans- Sea and ocean water are unfit for human consumption because they contain high levels of dissolved salts, making them saline.

4. How does groundwater get recharged?

Ans- Groundwater gets recharged primarily through the infiltration of precipitation (rainwater) into the soil, which percolates down to replenish underground aquifers.

5. What is aquifer? How is water present in aquifers pumped out?

Ans- An aquifer is an underground layer of rock or sediment that holds groundwater. Water present in aquifers is pumped out using wells, boreholes, or tube wells by applying pressure to push the water to the surface.

6. List the major factors responsible for depletion of water table.

Ans- Major factors responsible for the depletion of the water table include over-extraction of groundwater, scanty rainfall, increasing population leading to higher water demand, agricultural activities, urbanization, industrialization, and deforestation.

 

Fill in the blanks:

1.    Groundwater is obtained with the help of wells and boreholes.

2.    Due to the water cycle, the total water of the world remains constant.

3.    Seawater is salty in taste.

4.    The groundwater present between the layers of hard rocks below the water table is called an aquifer.

5.    Vegetation slows down the flow of rainwater on land and increases the absorption of water by soil.

 

Match the two columns.

Column A	Column B
1. Infiltration 2. Water table 3. Purest form of water 4. Increasing population 5. Ocean water	(i) Upper level of groundwater (ii) Scarcity of water (iii) Seepage of water (iv) Saline water (v) Rainwater

 

Ans-

1.    Infiltration - (iii) Seepage of water

2.    Water table - (i) Upper level of groundwater

3.    Purest form of water - (v) Rainwater

4.    Increasing population - (ii) Scarcity of water

5.    Ocean water - (iv) Saline water

 

Multiple Choice Questions (MCQs); 

Choose the correct answer for each of the following.

1. The percentage of water present in human body is

(a) 50%.

(b) 60%.

(c) 70%.

(d) 80%

Ans- (c) 70%

2. Which of the following factors are responsible for shortage of water?

(a) Increasing population

(b) Increasing industries

(c) Agricultural activities

(d) All of them

Ans- (d) All of them

3. Which of the following is a false statement?

(a) Water is required for cooking.

(b) Water is required for transport.

(c) Human beings use water for breathing.

(d) Water is required for photosynthesis.

Ans- (c) Human beings use water for breathing.

4. Plants need water for

(a) germination of seeds.

(b) transport of nutrients.

(c) photosynthesis.

(d) all of them.

Ans- (d) all of them

 

Additional Questions from text

1.   Why is water essential for living beings?

Ans- Water is essential for living beings because it is involved in several biological processes, including digestion, nutrient absorption, distribution of substances in the body, and waste excretion.

2.   What are some biological processes in humans and animals that require water?

Ans- Biological processes such as digestion of food, absorption of nutrients, distribution of various substances within the body, and excretion of body wastes require water.

3.   Describe the three states in which water exists.

Ans- Water exists in three states: solid (ice or snow), liquid (as we normally see it at room temperature), and gas (water vapor or steam).

4.   Explain the water cycle.

Ans- The water cycle is the continuous circulation of water from the Earth's surface to the atmosphere and back again. It involves processes such as evaporation, condensation, precipitation, and runoff.

 

Diagram

 

5.   What percentage of the Earth's surface is covered by water?

Ans- Nearly three-fourths (about 70%) of the Earth's surface is covered by water.

6.   Why is most of the Earth's water not suitable for human consumption?

Ans- Most of the Earth's water is not suitable for human consumption because about 97.5% of it is salty, and a significant portion of the remaining freshwater is frozen in glaciers and polar ice caps.

7.   What are the various sources of freshwater?

Ans- Various sources of freshwater include rainwater, surface water (rivers, lakes, and streams), and groundwater.

8.   Describe groundwater and how it is obtained.

Ans- Groundwater is water that seeps underground and is stored in aquifers or between layers of rocks. It can be obtained through wells, tube wells, springs, or hand pumps.

9.   How is water supplied in towns and cities?

Ans- Water is supplied in towns and cities through a network of pipes, which draw water from nearby rivers, lakes, ponds, or wells.

10. Why is water scarcity a problem, despite the Earth being covered with water?

Ans- Water scarcity persists despite the Earth being covered with water due to factors such as uneven distribution, pollution, overuse, and interference with natural water cycles.

11. What are some reasons for the depletion of the water table?

Ans- Some reasons for the depletion of the water table include scanty rainfall, increasing population leading to urbanization and construction, industrialization, agricultural activities, and deforestation.

12. How can water conservation be practiced?

Ans- Water conservation can be practiced by avoiding wastage (e.g., fixing leaks, turning off taps), using efficient irrigation methods, constructing dams and reservoirs, recycling water in industries, planting trees, treating sewage and factory wastes, practicing rainwater harvesting, and using biodegradable fertilizers and pesticides.

13. What is rainwater harvesting, and why is it important?

Ans- Rainwater harvesting involves collecting rainwater falling on rooftops and directing it into storage tanks or underground reservoirs. It is important for replenishing groundwater and conserving water resources.

14. Explain the importance of treating sewage and factory wastes before disposing of them into water bodies.

Ans- Treating sewage and factory wastes before disposing of them into water bodies is important to prevent water pollution and protect aquatic ecosystems and human health.

15. Define the water cycle and water table.

Ans- The water cycle refers to the continuous movement of water on Earth through processes such as evaporation, condensation, precipitation, and runoff. The water table is the level of groundwater below the Earth's surface, and infiltration is the process of water seeping deep underground.