Why Does Drought Occur?
Why does drought occur, why is drought experienced? Prolonged lack of precipitation, high temperatures, incorrect land use, and global climate change are the main causes of drought.
The Meteorological and Atmospheric Sources of Drought
Drought is fundamentally a meteorological event and primarily results from natural changes in weather systems. However, the duration and intensity of these natural changes have increased with climate change.
1- Anomalous Changes and Persistence in Precipitation Regimes
The primary cause of drought in a region is the insufficiency of precipitation amount for a period longer than normal. This usually happens when the air currents that bring precipitation to a region (such as Westerlies or Monsoons) weaken or change their route. The lack of adequate snowfall is also a cause of drought, as snow cover is an important reservoir that feeds groundwater as it melts. This chronic reduction in precipitation quickly depletes surface water and soil moisture.
2- Excessive Evaporation Caused by High Temperatures
Above-normal temperatures accompanying periods of reduced rainfall significantly increase evaporation (evapotranspiration). This causes soil moisture and water in dams to return to the atmosphere. Therefore, even if sufficient rain falls, this water is rapidly lost due to excessive heat, and the severity of the drought increases. The temperature increases caused by global warming make this meteorological effect permanent.
3- Large-Scale Climate Events (El Niño and La Niña)
Natural ocean-atmosphere phenomena like El Niño and La Niña, which result from changes in Pacific Ocean surface water temperatures, affect global air circulation. These major climate events overturn the expected precipitation and temperature patterns in different parts of the world, leading to excessive rainfall in some regions while causing prolonged and severe droughts in others.
Human-Caused (Anthropogenic) Drought Factors
While natural factors may initiate a drought, human intervention in nature significantly multiplies its effects.
1- Improper Land Use and Deforestation
Specifically, cutting down trees and deforestation severely reduces the soil's capacity to hold water. Forests act as a natural sponge, absorbing water and slowly releasing it into groundwater reserves. With the destruction of forests, the soil cannot retain water, surface runoff accelerates, and rapid drying occurs after floods. Furthermore, cultivating agricultural products with high water demands in dry regions excessively strains water resources.
2- Excessive and Uncontrolled Groundwater Pumping
When dams and surface water decrease, agriculture and industry often turn to groundwater. However, if the natural recharge rate of groundwater (through rainfall) is much slower than the pumping rate, this leads to a critical drop in groundwater levels. This is one of the biggest human-caused drought factors that jeopardizes the water resources of future generations, not just the present.
In conclusion, the occurrence of drought is the result of the combination of natural meteorological conditions with human actions (especially climate change, deforestation, and excessive water use). To mitigate the threat of drought, it is urgently necessary to adopt sustainable water management policies, transition to less water-consuming methods in agriculture, and prioritize the fight against global climate change. /
