Q2. Water cycle is responsible for maintaining the supply of freshwater on earth. But over the past years,human activities have affected the water cycle. Find out how human activities have affected the cycle and
the ways in which we can stop it.You can use an A4 size sheet.
Q5. The eastern coastal plain is hit by several cyclones every year. Some cyclones are not so intense butsome cause severe damage to life and property. Find out how the people living in the coastal region adjust
to such a life.You can use an A4 size sheet for your answer.
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1.
ARTICLE Humans and the water cycle EXPLORE
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We are becoming increasingly aware of our impacts on nature, but unfortunately many of the things we do have become so ingrained in our way of life that it is hard to change.
Earth’s water distribution
A number of human activities can impact on the water cycle: damming rivers for hydroelectricity, using water for farming, deforestation and the burning of fossil fuels.
Different countries use different amounts of water, but we all tend to use them in the same ways, and some of these actions can impact on the water cycle – generating hydroelectricity, irrigation, deforestation and the greenhouse effect, as well as motor vehicle use and animal farming.
Hydroelectricity
Most of New Zealand’s electricity is generated using hydro dams. This involves changing the stored gravitational energy of water held behind the dam into electrical energy that can be used. While this is a non-polluting renewable way to generate electricity, it does have environmental impacts – especially when mismanaged.
Clyde hydro dam
The Clyde dam in the South Island uses water to generate electricity. It is New Zealand’s third largest hydro dam.
Rivers must be dammed, which can affect the function of the river both upstream and downstream – lakes are usually formed from the water accumulating above the dam and a build-up of silt can occur, while the amount of water is reduced further downstream. This can be problematic for any plants and animals that may find themselves with too much or too little water, and migrating fish cannot get through the dams.
Seriously mismanaged dams can result in droughts downstream, with smaller streams completely drying up, leaving areas of unwatered land. People then have to look at ways of getting more water into these dry areas.
Find out more about hydro power.
Irrigation
As the human population has increased, so have our demands on the land. We need more food, and to make food, we need water. Irrigation is the artificial watering of land that does not get enough water through rainfall. Irrigation is used substantially by most countries, some more than others. Arid (dry) lands require far more water, as do countries that have large intensive farming communities.
Spray irrigator
Irrigation is a method used to water farm land. Unfortunately it removes water from rivers and can cause surface run-off and leaching.
The problem with irrigation is that it removes water from its natural source and often causes leaching and run-off where it is used. This removal of nutrients results in farmers using more fertilisers to keep their pastures productive while the waterways become polluted. Another problem is that salt is brought up from lower levels (salination).
Deforestation
The removal of trees (deforestation) is having a major impact on the water cycle, as local and global climates change.
Normally, trees release water vapour when they transpire, producing a localised humidity. This water vapour then evaporates into the atmosphere where it accumulates before precipitating back to the Earth as rain, sleet or snow. Deforestation in one area can therefore affect the weather in another area because if trees are cut down, there is less water to be evaporated into the atmosphere and subsequently less rain.
At a local level, the land becomes drier and less stable. When it rains, instead of the water being soaked up, there is increased run-off and leaching. Areas can become more prone to both droughts and flooding, impacting on plants and animals, and also humans living near deforested areas.
Dynamic and complex: the global water cycle
Water in the Earth system is influencing all aspects of life on Earth. Pathways, storage, transfers and transformations have an effect on the global climate and human welfare. Within this interactive 4 scientists talk about some of the complex aspects of the water cycle.
Greenhouse effect
The greenhouse effect is a natural phenomenon of Earth’s atmosphere trapping a range of gases, which in turn capture infrared radiation to keep our Earth at a moderate temperature range compared to the other planets in our solar system
Human activity such as the burning of fossil fuels has an effect on the overall increase of the Earth’s temperature. Raising the Earth’s temperature may mean that there is an increase of evaporation, melting of ice or other processes of the water cycle that adversely affect the climate on Earth.
2. The effects of tropical cyclones include heavy rain, strong wind, large storm surges near landfall, and tornadoes. The destruction from a tropical cyclone, such as a hurricane or tropical storm, depends mainly on its intensity, its size, and its location. Tropical cyclones remove forest canopy as well as change the landscape near coastal areas, by moving and reshaping sand dunes and causing extensive erosion along the coast. Even well inland, heavy rainfall can lead to landslides in mountainous areas.