Introduction
Drought is a complex phenomenon that is hard to define and different in different regions. Drought is not just a dry year, and there is a definition beyond that. Interestingly, drought is not at all a proper term for defining this situation, and the scientific and precise term is “dehydration”.

The dehydration period is a prolonged period in which an area with a shortage of resources and water storage faces many losses. According to this definition, the dewatering period should be measured in relation to one region and its different characteristics, and similar conditions cannot be considered for different regions.

Here are some the most important types of this phenomenon:

1. Climatic droughts: In this type of drought, we face a decline in atmospheric precipitation and a shortage of groundwater and surface water.

2. Agricultural drought: In this type of drought, evapotranspiration exceeds precipitation that cause the earth to lose its moisture, and plants cannot even grow up. In this type of drought, the quality and quantity of product cuts will be reduced and production of food reserves will be difficult.

3. Hydrological drought: Hydrology drought is a branch of science that examines the rotation, distribution, and quality of water above, on the surface of the earth and below it. The shortage of atmospheric depression affects the resources and water resources of the day and the underground, such as river flows, lake water levels and groundwater, and will not be detected soon. For example, a period of shortage of rainfall will immediately reduce soil moisture and affect the agricultural sector, but the impact of this period on the level of hydrocarbon deposits cannot be touched in the short term.

4. Economic-social droughts: Water is not, no one is able to produce food, so there is a shortage of food and unhealthy and mortal causes. The production of many economic commodities such as water, grains, fish, hydroelectric power and depends on the climate. Socio-economic drought is not due to depletion of excessive loss of precipitation and climate change results but rather to the design and planning of unscrupulous water resources management… ِDownload article

By: Hosam Zolfonoon PhD Environmental Engineering PhD Student, University of Coimbra, Portugal