This PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource will help you in revision during exams.
PSEB 7th Class Science Notes Chapter 16 Water: A Precious Resource
→ All living things need water to survive.
→ The three states of water are solid, liquid and gas.
→ Less than 1% of the world’s water is freshwater or out of all Earth’s water, only about 0.00367% is available for human consumption.
→ Our future depends on the availability of water.
→ Every year March 22 is celebrated as World Water Day.
→ The minimum recommended amount of water per person is 50 Litres per day.
→ Water scarcity has become a global concern.
→ About 71% of the earth’s surface is covered by water.
→ Almost all the water on the earth is found in the oceans, seas, rivers, land, and atmosphere.
→ Useful water is freshwater.
→ Salt-free water present on Earth is 0.006% of the total amount of water available on Earth.
→ In solid-state water is present as ice and snow found in the snow-covered mountains at the poles of the earth and as glaciers.
→ Water in the liquid state is found in oceans, lakes, rivers as well as groundwater below ground level.
→ In the gas state, water is present in the air in the form of Vapours in the atmosphere.
→ Rainwater is considered to be the purest form of water.
→ The transfer of water is done by the water cycle.
→ The main source of water is groundwater.
→ Groundwater accumulates in the layers of stable hard rocks.
→ Population growth, increase in industrial and agricultural activities, etc. affect the groundwater level.
→ Groundwater level decreases due to high utilization of groundwater and low absorption of water by land.
→ Rainwater is used for rainwater harvesting.
→ Factors affecting groundwater levels are deforestation and excessive water absorption.
→ Bawris and Drip irrigation systems are some of the techniques that can be used to meet water scarcity.
→ Without water, greenery will disappear from the earth, which means the end of life.
→ Time demands that everyone should use water sparingly. Hence the unwanted and excessive use of groundwater should be avoided.
→ When plants are not watered for a few days, they wither away and eventually die.
→ The Punjab Government had passed the Water Conservation Act 2009 of Punjab in the year 2009 under which the date of transplantation of Paddy crop for the first time was fixed on 10th June. This was later changed to June 15, 2015.
→ The Dead Sea is a salty lake bounded on the east by Jordan and on the west by Israel and Palestine.
→ It is 8.6 times saltier than the other oceans having more alkalinity, the cause non-existence of plants and living creatures, which is why it is called the Dead Sea.
→ Water Cycle: Many processes such as evaporation of water into the air, formation of clouds through condensation, and the occurrence of precipitation which maintains water on the earth, even though the whole world uses it is called the water cycle.
→ Fresh Water: The water that is suitable for drinking is freshwater. It contains a very small amount of salt. This is about 3% of the total water on earth, which is found in rivers, lakes, glaciers, snow-capped peaks, and underground.
→ Water table: At a depth near the water source where the space between the rocks is filled with water is called groundwater area or saturated area. The surface of this water is called the water table.
→ Wet Rock layer: Groundwater between layers of hard rock below the water table is called the wet rock layer. This water is drained through tube wells.
→ Infiltration: Water from various sources such as rain, rivers, and ponds is going even deep inside the earth due to gravity. This is called infiltration.
→ Water management: The efficient distribution of water is called water management.
→ Drip Irrigation System: This is an irrigation technique in which water is dripped through pipes to the plant.
→ Water Storage: The process of collecting rainwater and using it when needed is called water storage. This is done to compensate for the water level.
→ Bawris: This is the ancient method of water storage. This method is still practiced in many parts of India today.