Drought is a continuous period of dry weather when an area gets less than its normal amount of rain. Droughts can last months or even years. Because crops and other plants need water to grow and land animals need water to live, droughts can be dangerous. Because of the lack of water, famine occurs and sometimes deserts are created. Many people die every year in famines that are due to drought in subsistence farming areas. Sometimes conflicts can occur because of drought.
A drought is a natural event that is caused by other weather events like El Niño, high pressure systems, and global warming. Drought can be triggered by people as well. Deforestation (people cutting down trees in forests and not replanting more trees), diverting (redirecting) rivers, and emptying lakes are ways that man interferes with nature and can cause drought.
It is often difficult to determine a specific time when a drought started because a drought is a disaster that usually takes place slowly. Its effects often build up slowly over a long time and may last from months to years, even after rain resumes.
Causes of drought
Lack of Rain (precipitation)
- See also: Precipitation
Water can fall in three ways from the sky:
- Water that falls as a liquid and stays a liquid
- Water that falls as a liquid and freezes when it touches the ground
- Water that is already frozen and falls as ice.
Droughts occur mainly in areas where the normal levels of rainfall are already low. If it rains a little less than normal over time, a drought will happen. Wind can also be one of the factors in a drought when there is already a lack of rain. If a dry wind blows (like a wind from over the land) rather than a more humid wind (like a wind from over the ocean), it can dry the land faster.
In the tropics (the areas of the earth that are closest to the equator), there are distinct wet and dry seasons. During the wet seasons, the area becomes a Monsoon trough because monsoons are pulled into the movement of air. During the dry seasons, the Intertropical Convergence Zone (Monsoon trough) moves dry air through the tropics. The movement of dry air eventually causes watering holes and rivers to dry up. This means that many grazing animals like zebras, elephants, and wildebeest are faced with a choice: move (migrate) to where there is water or die. The fruit and vegetable-bearing plants that are left ripen faster because evaporation and transpiration from the plants are increased. Bushfires are common during the dry season as well because of the lack of water in the remaining plants.
- See also: El Niño
El Niño is a natural event that takes place when seawater temperature rises in the tropical Pacific Ocean. This changes the atmospheric pressure between the Pacific and Indian Oceans. Since atmospheric pressure determines weather, during El Niño we see drought in some areas of the world and heavy rainfall in other areas.
Erosion and human activities
- See also: Aeolian processes
Erosion is a process in which natural forces like wind, air, water, and gravity cause the earth to move or wear away. In dry, or arid, climates, the main source of erosion is the wind. Because the soil is already dry, wind can lift small particles and move them to another region. Particles that are suspended in the wind may rub against solid objects and cause erosion by abrasion. Wind erosion usually happens in areas where there is not enough rainfall to grow many plants.
Loess is a type of soil that is affected by wind erosion. It looks like little cliffs of sand and is common in the middle of the United States and other areas of the world like China, Hungary, and Belgium. Windbreaks (like large trees and bushes) are planted on and near loess to help block as much wind as possible.
- See also: Climate change
Scientists expect that because of global climate change, droughts will be triggered. Overall, they state that global warming will result in more rain falling all over the world, but areas that are prone to drought will increase as well. Some of the suggestions to fight global warming, however, involve the use of a space sunshade, which may also increase the chances of drought.
Types of drought
As drought continues, the conditions surrounding it gradually worsen and those living in drought areas are more affected. People define droughts in three main ways:
- Meteorological drought happens when there is a prolonged time that an area receives less than its average precipitation. Meteorological drought usually comes before other kinds of drought.
- Agricultural drought affects crop production or the ecology of a distinct area. This can happen because of poorly planned farming areas. The water that is available in the area has a hard time reaching the plants or erosion occurs. Meteorological drought conditions can affect agriculture as well.
- Hydrological drought happens when the water in reserves like aquifers, lakes, and reservoirs drop below their normal amount. We see the effects of hydrological drought more slowly because it involves stored water that is used or moved but not refilled. This can be caused by people using or moving water or by a lack of rainfall.
Consequences of drought
The consequences of droughts and water shortages can be divided into three groups:
- Environmental: Water levels drop and there is a lower flow of water. This lack of water is dangerous for animals that live in water. We see more pollution on the surface of the water. Wetlands dry out, causing more and larger fires. Wind erosion happens more easily, and plant life has a hard time surviving because of lack of water, pests, and diseases. Animals have to move because of the lack of water and plants.
- Economic: Farming is less successful during a drought, which means the price of groceries is affected because there is less food to sell. Livestock is more difficult to care for during a drought. Forests have fewer healthy trees and fewer animals. Energy production decreases in hydro plants (businesses that use water to make energy). Tourism even decreases because activities that involve water have a harder time working correctly.
- Social: People's health can be affected by heatwaves and having to use less water. People can become stressed due to higher food costs and the lack of other things that are normal in their life. Drought also results in snakes moving closer to water and food in residential areas resulting in more snake bites. Less-developed countries have more difficulties with water shortages because they do not have the same helpful equipment as more-developed countries. Sometimes they have to move because of pollution or lack of water. War can even break out because people or countries could begin fighting over food and water.
History of drought
Drought is a normal part of the cycle of the climate in most parts of the world. It is written about in the Epic of Gilgamesh and the Biblical story of Joseph. Historians believe that people migrated out of Chile and Africa thousands of years ago because of drought.
Well-known historical droughts include:
- 1900: a drought in India that killed between 250,000 and 3.25 million.
- 1921-22: a drought in the Soviet Union in which over 5 million died from starvation
- 1928-30: a drought in Northwest China resulting in over 3 million deaths by famine.
- 1936 and 1941: droughts Sichuan Province China resulting in 5 million and 2.5 million deaths respectively.
- The 1997-2009 Millennium Drought in Australia led to a water supply crisis across much of the country. As a result, many desalination plants were built for the first time.
- In 2006, Sichuan Province, China, experienced its worst drought in modern times with nearly 8 million people and over 7 million cattle facing water shortages.
- A 12-year drought that was devastating southwest Western Australia, southeast South Australia, Victoria, and northern Tasmania was "very severe and without historical precedent".
- In 2005, the Amazon basin experienced its worst drought in 100 years.
- Recurring droughts in East Africa have caused desert areas to grow. This is called desertification.
- In 2012, a severe drought struck the western Sahel. 10 million people were at risk of famine and almost $1 billion was sent to help.
Protection, mitigation and relief
Farmers can lessen the effects of (mitigate) drought by properly watering and rotating their crops. Agencies have been formed to focus on soil preservation. This began in 1935 after President Roosevelt signed documents creating the Soil Conservation Service. The name has since been changed to the Natural Resources Conservation Service.
Here is a list of ways that we can protect against drought, lessen the effects of drought, and bring relief to those who are affected by drought:
- Cloud seeding: This is a form of purposely changing the weather to bring rainfall. This remains a hotly debated topic and there is not yet scientific proof that it would work.
- Dams: Many dams and their associated reservoirs supply additional water in times of drought.
- Desalination: Removing salt from seawater could make more fresh water available for watering plants and drinking.
- Drought Monitoring: If we can closely watch and measure rainfall levels and compare them with current water usage, it could help prevent man-made drought.
- Land use: Carefully planned crop rotation can help to minimize erosion and allow farmers to plant less water-dependent crops in drier years.
- Outdoor water-use restriction: Regulating the use of sprinklers, hoses, or buckets on outdoor home maintenance can help prevent drought. In drier climates, it is popular to Xeriscape yards. Planning the landscaping in a way that requires little or no watering is a good way to preserve water.
- Rainwater harvesting: We can collect and store water that is already given to us naturally. Rainwater from roofs or other surfaces can be used when we would normally use a hose.
- Recycled water: Former wastewater (sewage) that has been treated and purified can be reused.
- Transvasement: We can build canals or redirect rivers toward drought-prone areas.
Quick facts about drought
- Drought is a time when the land is too dry.
- Drought can be caused by nature or by man.
- When areas do not get enough rain, drought happens.
- Weather patterns can bring about drought.
- Erosion of soil can cause drought.
- Humans can bring about drought by deforestation or using too much water.
- Drought can have serious consequences: It can be bad for the environment and living things in certain areas, it can cause changes in the economy of an area or country, and it can affect the health of people.
- There are many ways that people can help prevent drought and help areas that are naturally prone to drought.
Drought Facts for Kids. Kiddle Encyclopedia.