The Six Main Causes of Drought

A drought or drouth is an event of prolonged shortages in the water supply, whether atmospheric (below-average precipitation), surface water or ground water. A drought can last for months or years, or may be declared after as few as 15 days. It can have a substantial impact on the ecosystem and agriculture of the affected region and harm to the local economy. Annual dry seasons in the tropics significantly increase the chances of a drought developing and subsequent bush fires. Periods of heat can significantly worsen drought conditions by hastening evaporation of water vapour. Here we discuss the six main causes of drought.

Drought is a recurring feature of the climate in most parts of the world.

Many plant species, such as those in the family Cactaceae (or cacti), have drought tolerance adaptations like reduced leaf area and waxy cuticles to enhance their ability to tolerate drought. Some others survive dry periods as buried seeds. Semi-permanent drought produces arid biomes such as deserts and grasslands. Prolonged droughts have caused mass migrations and humanitarian crisis. Most arid ecosystems have inherently low productivity. The most prolonged drought ever in the world in recorded history occurred in the Atacama Desert in Chile (400 Years).

Drought affect food production and human society, so they are considered a disaster, of natural, supernatural or human cause (which itself could be supernatural causes, malediction, sin, …). It is among the earliest documented climatic events, present in the Epic of Gilgamesh and tied to the Biblical story of Joseph’s arrival in and the later Exodus from Ancient Egypt. Hunter-gatherer migrations in 9,500 BC Chile have been linked to the phenomenon, as has the exodus of early humans out of Africa and into the rest of the world around 135,000 years ago. Rituals exist to prevent or avert drought, rainmaking could go from dances to scapegoating to human sacrifices. Nowadays, those ancient practices are for the most part relegated to folklore and replaced by more rational water management.

Types of drought

People tend to define droughts in three main ways:

Meteorological drought occurs when there is a prolonged time with less than average precipitation. Meteorological drought usually precedes the other kinds of drought.
Agricultural droughts affect crop production or the ecology of the range. This condition can also arise independently from any change in precipitation levels when either increased irrigation or soil conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops. However, in a traditional drought, it is caused by an extended period of below average precipitation.
Hydrological drought is brought about when the water reserves available in sources such as aquifers, lakes and reservoirs fall below a locally significant threshold. Hydrological drought tends to show up more slowly because it involves stored water that is used but not replenished. Like an agricultural drought, this can be triggered by more than just a loss of rainfall. For instance, around 2007 Kazakhstan was awarded a large amount of money by the World Bank to restore water that had been diverted to other nations from the Aral Sea under Soviet rule. Similar circumstances also place their largest lake, Balkhash, at risk of completely drying out.

The “new normal” of water management across the United States suggests we need to consider the regions we live in are either heading into a drought or coming out of a drought. California is in a mega drought and most data indicates water is becoming more available. Georgia is heading into a drought. For the past year things have been getting worse and according to the U.S. Drought Monitor today over 30% of the state is in a severe drought. This is nothing like the drought of 2008 when Atlanta was days away from running out of water, but as cycles go, they are headed into a drought and it’s hard to say when it will end. Ohio, who has been in a sports championship drought and moving out of it is headed into a water drought.

The Six Main Causes of Drought

  1. Land and water temperatures cause drought. As overall temperatures increase more water evaporates and severe weather conditions increase. Landscapes and crops need more water to survive and overall the demand for water increases. This is why it is so important to consider changes in ET when discussing water savings. You might be using more water or less water depending on weather conditions.
  2. Air circulation and weather patterns also cause drought. Key events like El Nino or La Nina help contribute to drought in areas. All the water we ever had we have today and it is stored in the air or on land. Weather patterns move the water in the air around. This is constantly changing.
  3. Soil moisture levels also contribute to drought. When soil moisture is depleted there is less evaporation of water to create clouds. Surface temperatures rise, more water is needed and less is available which contributes to a more severe drought.
  4. Drought can also be a supply and demand of water issue. When a region is growing rapidly the demand for water can exceed the supply. When weather conditions, temperatures or air patterns push a region toward a drought the demand for water by people can offset or worsen the situation depending on how the region reacts. Excessive irrigation is an excellent of people contributing to a drought.
  5. If the timing of water doesn’t match the agricultural season you may have too much water when you don’t need it and too little when you do need it. Proper storage and collection of water is key to counter balancing this cycle and clearly in the scope of human management.
  6. Overall, global warming will result in increased world rainfall. Activities resulting in global climate change are expected to trigger droughts with a substantial impact on agriculture throughout the world, and especially in developing nations. Along with drought in some areas, flooding and erosion could increase in others. Some proposed solutions to global warming that focus on more active techniques, solar radiation management through the use of a space sunshade for one, may also carry with them increased chances of drought.

Severe droughts also impact the migration of people. As countries continue to protect their natural resources people will move to water. The amount and timing of the movement can contribute to water issues not previously felt before.

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