what is drought & what are its effects & causes?

A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. Although droughts can persist for several years, even a short, intense drought can cause significant damage and harm the local economy.

CAUSES:
1-Because drought is defined as a deficit in water supply, it can be caused by a number of factors. The most important one though relates to the amount of water vapor in the atmosphere as this is what creates precipitation. More rain, sleet, hail, and snow can occur where there are moist, low pressure air systems. If there is an above average presence of dry, high pressure air systems instead, less moisture is available to produce precipitation (because these systems cannot hold as much water vapor). This results in a deficit of water for the areas over which they move.

2- The same can also happen when winds shift air masses and warm, dry, continental air moves over an area as opposed to cooler, moist, oceanic air masses. El Nino, which affects the ocean's water temperature, also has an impact on precipitation levels because in years when the temperature cycle is present, it can shift the air masses above the ocean, often making wet places dry (drought prone) and dry places wet.

3-Finally, deforestation for agriculture and/or building combined with the resultant erosion can also cause drought to begin because as soil is moved away from an area it is less able to absorb moisture when it falls.

drought is a natural calamity due to the lack of water . the main reason is less amount of rainfall .  this may cause a famine .  this may effect the nature the trees and grass may dry up .