CBSE Class 7 Science Revision Notes Chapter 16

CBSE Class 7 Science Revision Notes Chapter 16 – Water: A Precious Resource

Water: A Precious Resource Class 7 Revision Notes by Extramarks is designed to help students thoroughly understand the chapter and its content. Class 7 Science Chapter 16 Notes are written by subject matter experts as per the revised CBSE Syllabus. These revision notes are easily accessible from the website at all times. They make study time easier and preparation better structured so students can score well in examinations.

Revision Notes for CBSE Class 7 Science Chapter 16 

Access Class 7 Science Chapter 16 – Water: A Precious Resource

Water

Water is the primary constituent of the hydrosphere and an inorganic chemical substance. It is a tasteless, clear, odourless, and nearly colourless substance found in nearly all known living organisms. It contains no calories or organic nutrients, but it is essential for all known forms of life.

Forms of Water:

On Earth, water generally exists in three forms:

Solid: Solid form of water is found in the form of ice at the poles, on snow-covered mountains, and on glaciers.

Liquid: A liquid form of water is found either in water bodies such as oceans, lakes, ponds, and rivers, or underground where it seeps below the surface through soil that collects over non-porous rocks (aquifers) present belowground.

Gas: Gaseous form of water is found as water vapour in the air.

Water Scarcity

Scarcity of Water

The water found underground is thought to be the purest form of water and the best for drinking. However, there is scarcity as the water column or water table present underground is continuously depleted. The following are the primary reasons for this:

• Due to population growth, there are fewer places where water can seep through the ground.
• The increasing expansion of the industry has had a significant impact on how much water is used in various industrial processes.
• Many agricultural areas use groundwater due to irrigation system failure caused by irregular rainfall. 
• The uneven distribution of rainfall has also reduced the water table in many places.
• The roots of trees often help in the retention of run-off water, but as a result of deforestation, water flows to lower areas rather than seeping through the soil. This affects water table drops.

Preventing Water Scarcity

Sustainable Water Management: Water storages can be built for conservation and smart irrigation systems can be utilised to achieve sustainable water management.

Reclaimed Water: Rainwater harvesting and wastewater recycling can help to relieve groundwater pressure. Rainwater can also be captured by digging pits in various locations.

Sewage Treatments: Wastewater discharged by households or factories can be treated and reused in sewage treatment plants. Sewage treatment will help improve water quality.

Water Waste Awareness Programs: Water waste awareness programmes should be held to educate people about water waste and how to avoid it. Small and necessary actions that can help with future water scarcity must be taught.

Depletion of the Water Table

Water depletion refers to a scarcity of water. Rainwater seepage replenishes the underground water level. The water table is not affected as long as we draw the same amount of water that is replenished by natural resources such as rain.

Reasons Behind the Depletion of Water Table

The depletion of the water table can be attributed to a number of factors.

• Water Over-Pumping: Groundwater is water that flows into the ground and is stored. This groundwater can be collected by drilling or digging wells, as well as pumping. Overpumping this water reduces groundwater volume. Excessive pumping in coastal areas may cause saltwater to migrate inland and upland, contaminating the water supply.
• Deforestation: Large-scale deforestation has occurred to feed the world’s growing population and provide space for industries. Cattle overgrazing has also resulted in significant vegetation loss. The green vegetation cover is essential to slow the flow of water and increase the soil’s absorption of water. Cutting down trees and plants interferes with the natural mechanisms of maintaining ground water level through water seepage and its storage in the ground, causing depletion.
• Increased Industrialisation: Water is used by all industries. Everything we use requires water during the manufacturing process. The number of industries is constantly increasing. The majority of the water used in the industry comes from groundwater. This results in water drainage.

Groundwater as an Important Source of Water

What is Groundwater?

Groundwater is water that has accumulated beneath the earth’s surface. Water seeps through the surface and is absorbed by the mud. Groundwater is obtained by drilling or digging a well, or by pumping. Overpumping of groundwater must be avoided as it affects the salinity of the soil. It lowers the water level and increases the salinity of the soil. Groundwater is also less expensive, more convenient, and less prone to contamination than surface water.

Infiltration

The process through which surface water seeps into the soil is known as infiltration. The rate of infiltration measures how quickly rainfall or irrigation can be absorbed by the soil.

Aquifer

An aquifer is a water-bearing permeable rock, a rock fracture, or unconsolidated material (gravel, sand, or silt) and from this groundwater can be extracted using a water well.

Water Availability and its Forms

The Earth is made up of 71 percent water, but only a small portion of it is fresh water. Over 97 per cent of the available water is salt water, which cannot be consumed. The remaining 3 percent is freshwater, of which 77 percent is frozen in the form of ice caps, glaciers, and so on, and groundwater accounts for 22 per cent of the freshwater. The remaining one per cent is found in rivers, lakes, ponds, streams, and so on.

Forms of Water

The three states of matter—solid, liquid, and gas—all contain water. Water is in its normal state when it is liquid. Water in its solid state is ice, and water in its gaseous state is vapour. One of the few substances which are heavier in its liquid state than its solid state is water.

Water Resources in India

In comparison to the rest of the world, India receives heavy precipitation (rain and snow). In comparison to the global average of 700 mm, India’s annual precipitation is 1170 mm.

Water Management

It is the responsibility of the nation to plan, develop, distribute, and control the inefficient use of water resources. Overflowing water supply pipes and a lot of water gushing out of the pipes is a waste of water. It is the civic authorities’ responsibility to prevent such waste of precious water. Mismanagement or waste can also occur at the individual level. Individuals should also exercise caution and avoid wasting water.

Here are Some of the Ways of Managing Water

Drip Irrigation: Drip irrigation is a type of irrigation that saves water and fertiliser by slowly dripping water into the roots of various crops, either on the soil surface or directly into the root region, via a network of valves, pipes, tubing, and emitters. This method saves more water than traditional irrigation.

Water Harvesting: Rainwater harvesting is the collection and storage of rainwater for on-site reuse rather than letting it run off. Rainwater is collected here and stored for later use.

Cultivating Better Habits: There are many ways to save water. One can utilise effective strategies to save water. For example, utilising lesser water while washing clothes, repairing leaking faucets, or taking a short shower rather than a long one.