Did you observe that after heavy rain, the top soil get washed off.
What will happen if the top soil is washed off?
How can we prevent it ?
We know that most of the organic matter is found as nutrients on the upper layer of soil and make it fertile. Storms and floods wash away or erode this fertile layer and the soil becomes barren. The loss of the upper fertile layer of soil is known as soil erosion.
Let us do an activity to see how soil is washed off.
Aim: To Know about soil erosion.
What to do: Cut three disposable bottles sidewise and fill with soil as shown in the figure. Put some sprouts of green gram or any other seeds in one bottle and water regularly. Cover the second bottle with dry leaves and leave the third bottle without sowing anything. In a week days the sprouts in the first bottle will grow more. Now make arrangement to collect the drained water from each bottle by arranging small vessels. Now blow air and pour equal amount of water slowly, in each bottle. Observe and record from which bottle less soil is blown out by air and washed off by water.
From this activity we can infer that top soil is washed off by air and water. Plants help to prevent soil erosion.
What are the other causes of soil erosion?
Apart from storms, floods and rains, unplanned and excessive usage of agro chemicals over grazing, deforestation, digging the earth for construction and mining also cause soil erosion. Due to soil erosion, the nutrients in the top soil is washed away and as a result the crop production decreases. Hence the soil erosion is to be prevented. Preventing the degradition of soil is called soil conservation. We can conserve the soil by:
- Controlling the destruction of forests.
- Growing trees in areas where there was no previous tree cover (Afforestation).
- Constructing dams, reservoirs and bunds
- Planned modern agricultural practices
- Crop rotation to retains soil fertility.
- Planting trees as shelter belt (wind breaks) reduces the effect of winds
- Preventing overgrazing, of land by animals.
- Not leaving the land vacant without any vegetation.
We have learnt that soil is an important natural resource and we need to conserve it.
Let us now learn about another important natural resource – Water.
Water – A Precious resource
On account of World Water Day, i.e. 22nd of March, Purvika participated in the fancy dress compititon ‘Water’ with a tag – “Water is precious. Save every drop.”
We know that water is a precious resource, let us know how much water is available for our usage.
Do You Know?
Water action decade 2018-2028
The UN General Assembly announced that the world will face 40 percent shortfall in freshwater resources by 2030 coupled with a rising world population the world is careening towards a global water crisis. Recognizing the growing challenge of water scarcity UNO launched the Water Action Decade ( 2018-2028) on 22 March 2018, to mobilize action that will help and transform our veiws of management of water.
Observe the above table and answer the following question given below.
♦ Is water from seas and oceans useful for drinking and agriculture?
♦ Where is fresh water available from?
♦ How much percentage of fresh water is available?
We understand that only one percent of water from surface and ground water sources is available for our domestic needs. The United Nations has recommended a minimum amount of water 50 litres (Two and a half buckets) per person per day for his daily activities and maintaining proper hygiene.
Think and Respond
There is huge amount of water on earth, then why is water called a precious resource?
All the places on earth do not have access to surface water sources for their needs. There ground water is used for drinking, agriculture and many other purposes.
The rivers and lakes get water through rain water. But how does the water reach the ground?
Ground water as an important resource
How does water reach the ground?
The rainwater moves down through the soil and fills the spaces and cracks deep below the ground as Ground water. This process of entry of water into the ground is called Infiltration. The upper level at which water stands in the ground is called water table.
Is the water table level same at all places?
The water table varies from place to place. It may be at a depth of less than a meter (near the bank of a river) or may be several meters below the ground (as in a desert).
Ground water is stored between layers of hard rock below the water table. This is called Aquifer. The wells, tube wells and hand pumps, get water present in the aquifers.
We have learnt how the water reaches the ground. Let us see the causes for the depletion of water table.
Depletion of Water Table
As many people are using ground water for their needs, will it be available for our future? Why do wells dry up?
Let us do the following activity to analyse the consequences of industrialisation and urbanization on the Ground water table.
Inquire from your grandparents about the difference in water table in your locality due to increase in the constructions and industries nearby and discuss in the class.
The groundwater gets replenished naturally by the see page of rainwater. However the water table may go down if the ground water is being used at a faster rate than it is being renewed by the natural process. Some ofthe factors which deplete the water table are: Population explosion, Increased industries and agriculture activities, Deforestation, decrease in the effective area for seepage and Scanty rainfall.
What will happen if the ground water table go down?
Are the water resources being increased along with our increased needs? Why?
Think and Respond
A thirsty crow finds an earthen pot with little water in it. Collects pebbles and drops in the pot. The water rises up and the happy crow quenches its thirst. The world appreciates its tact. But, the crow which knows only to drop pebbles and get water, dies of thirst after few days.
The reason is crow tried only to draw the leftover water in the pot but never tried to increase the water in it.
Man for his needs found the water under the ground.
Rigged the earth, inserted pipes, set motors and drew water.
His needs were fulfilled. Man who utilised the resources never tried to save or conserve them, falls in a danger. If the situation still continues, won’t it happen to man same as that happened to the clever crow.
Most of the times we do not think about the importance of fresh water. You might be living in an area where there is sufficient rainfall, yet there is shortage of drinking water. Can we attribute this to mismanagement of water resources?