Natural causes
Some droughts have occurred naturally, plaguing humankind throughout much of our history. Until recently naturally occurring droughts were often natural phenomena triggered by cyclical weather patterns, such as the amount of moisture and heat in the air, land, and sea.
The distribution of rainfall around the world can also be impacted by how air circulates through the atmosphere. When there is an anomaly in surface temperatures, particularly over the sea, air circulation patterns are altered.
This changes how and where precipitation falls around the world and the new weather patterns will most likely throw water supply and demand out of sync, as is the case when earlier-than-usual snowmelt reduces the amount of water available for crops in the summer.
Drought can also result because of an imbalance in the supply and demand of water. As the global human population continues to balloon, and intensive agricultural practices continue to be employed, more water is required to sustain the human race as well as the agricultural practices. This continues to tip the scales, making droughts a reality with each passing day.
A study estimated that between 1960 and 2010 the human consumption of water increased the frequency of drought in North America by 25%. The situation is worsened by dwindling rainfalls, forcing people to pump more water from rivers, aquifers and reservoirs. Doing this depletes valuable water resources that could take years to replenish and could permanently impact future water availability.
At the same time, demand for water supplied by upstream lakes and rivers, particularly in the form of irrigation and hydroelectric dams, leads to the diminishing or drying out of downstream water sources, further contributing to droughts in other regions.
Deforestation and soil degradation
Trees and plants are important as they release moisture to the atmosphere, resulting in clouds forming and rainfall falling, returning the moisture to the ground. Unfortunately, the human race is the best at destroying these natural resources.
When forests and vegetation disappear, less water is available to feed the water cycle, making entire regions more vulnerable to drought. Meanwhile, deforestation and other poor land-use practices, like intensive farming, continue to diminish soil quality and reduce the land’s ability to absorb and retain water.
As a result, soil dries out faster, inducing agricultural droughts, and less groundwater is replenished, contributing to hydrological drought.
As the name suggests, the planet is being warmed at alarming rates and could result in droughts. Global warming is mostly associated with human activity such as releasing greenhouse gases which cause a trapping effect, causing global temperatures to rise.
With increased temperatures, water from rivers, streams, lakes and other bodies of water will continue to evaporate and other practices will result in less of it coming back down as rain. This will therefore result in less rainfall and of course droughts.
Rising temperatures have the effect of making wet regions wetter and dry regions drier. For wetter regions, warm air will absorb more water, leading to larger rain events while in more arid regions, warmer temperatures mean water evaporates more quickly.
Climate change also alters large-scale atmospheric circulation patterns, causing a shift in storm tracks off their typical paths. This, in turn, magnifies weather extremes, which is one reason why climate models predict the already parched U.S. Southwest and the Mediterranean will continue to get drier.
