NCERT Class 7 Science Chapter 16 Water a Precious Resource

Water a Precious Resource – In this article, we will study the topic Water a Precious Resource from chapter 16 out of Class 7 Science. Water resources are natural resources of water that are potentially useful.

Availability of Water

There is only 71% water is on the earth’s surface out of which a small amount is available for human use.

Above figure shows the water content on earth. The bucket represents the total water on earth. Out which freshwater is shown in the mug, the glass if water represents groundwater. One-fourth of spoon represents water in lakes and river in the world.

Water that issued for human consumption is the freshwater. As per the reports, only 0.006% of water is available for us.

Water cycle

In nature, water exists in three forms

Solid-ice caps. Snow-covered mountains and glaciers.
Liquid-oceans, lakes river and underground water.
Gas-water vapor in the air.

The state of water it keeps on changing in all three states. This process of changing states of water is known as the water cycle. The cycle helps to keep water on the earth in a constant state.

The water cycle is known as the hydrological cycle or hydrologic cycle. It involves the exchange of energy which leads to climatic changes.

Processor steps involved in the Water Cycle

Evaporation

It is the process of transformation of water from liquid to gaseous state. Water from earth’s surface evaporates and turns into vapor

It includes transpiration from the plant where water vapor also comes from green plants.

Most of the water that evaporates from the ocean falls back into the ocean as precipitation.

Heat energy is important for evaporation.

Condensation

It involves the transportation of water into liquid states. The water vapor condenses to form a cloud.

Here the water vapors are converted into water by cooling.

It is very crucial in water cycles as it forms clouds.

It is also responsible for ground-level fog.

Precipitation

In this process, waterfalls from the sky in the form of rain, snow, hail or sleet. Most precipitation takes place due to rain. At high altitude, the condensed water from the clouds falls in the form of ice.

Collection

After the precipitation process, the waterfalls on the ground and gets collected in the surrounding water bodies. Some water seeps down to recharge the groundwater while rest flows into the ocean via the river.

Water evaporates again and continues the cycle.