Drought

A Drought is categorised as a natural disaster often identified as the antipode of extreme precipitation events such as flooding, with these coming as a result of an area or region experiencing a period of time with below normal precipitation that often coincide with high temperatures. These events range in the length of time that a region experiences them from a few days to periods of months and even years, with the social, economic and environmental impact of such events increasing as the events continue.

There are four main categories in which droughts can be classified these are:

Meteorological Droughts: A drought specific to a region or area depending on the average annual precipitation for that region. As such if a region experiences a year of precipitation that falls below that of the average annual precipitation value for the region it is categorised as being a meteorological drought. This value however is purely statistically defined, meaning that if a region that has a high average precipitation value experiences an annual precipitation that falls short of the historic average the region will be declared as having a meteorological drought independent of the impact on the environment.

Hydrological Drought: A drought that refers to a prolonged and persistent period of low water volumes experienced throughout surface water systems including streams, rivers, lakes and reservoirs. These droughts often coincide with meteorological droughts coming as a result of reduced precipitation and changes in climatic characteristics of a region. A hydrological drought can also be further exacerbated by anthropogenic activity with a maintained need for water for human usage leading to a drawdown on the remaining water resources within reservoirs exacerbating the issue.

Socioeconomic Drought: A socioeconomic drought refers to a period where the demand for water exceeds the available supply. This often occurs in regions that require too much irrigation for crops in comparison to the annual precipitation of a region and the water resources that are available as well as in the event of hydroelectric power generation being reduced as a result of reduced flow within river systems.

Agricultural Drought: This form of drought is specific to the agricultural sector accounting for the water needs of individual crops during a growing season as such if the required water and moisture needs are not met during a phase of growth this can negatively impact the crop overall yield. As such an agricultural drought remains persistent until precipitation exceeds that of the daily evapotranspiration.

These events are only set to increase in prevalence with continued anthropogenic climate change affecting both the precipitation and temperature settings of regions across the world. The change in the environmental characteristics of a region could lead to an increase in the overall percentage of land that is impacted by these events as well as further exacerbating regions currently experiencing drought conditions.

Impacts

The below normal precipitation compounds within the environment leading to reduced soil moisture, reduced groundwater recharge, diminished stream flow in surface water systems, crop damage as well as widespread water shortages. Drought events are also some of the most common and far reaching with an estimated 40% of the total population of the world being at risk of being affected by drought conditions. This can cause wider impacts not only to the natural environment itself but also to the societal and economic sectors as well, the impacts of droughts include:

Economic losses such as agricultural activity with the loss of crops and livestock
Societal changes with population migration to avoid the impacted regions putting further strain on the available resources that can lead to conflict.
Reductions in the overall quality and quantity of available water resources.
Ecosystem damage with flora and fauna being unable to sustain themselves as a result of reduced resources. With droughts also being linked to an increase in the potential for wildfires as is seen in Western USA.
Human health can also be severely impacted with an increase in heat stroke and even loss of life being attributed to drought events.

Mitigation

The mitigation of drought events is not an easy task to undertake as the cause of these events is linked to the wider climate and the changing climatic setting of a region. In many of the impacted regions governmental discretion is often used to limit the usage of water resources in order to sustain and protect the already diminishing resources for as long as possible along with improved water use planning for impacted areas. Other novel approaches have been used such as covering reservoirs to reduce the evaporation of water resources as well as rain-water harvesting, improved management of water abstraction and channel management to reduce the amount of water that is lost through infiltration.