DROUGHT Drought is an environmental extreme that is characterized by an absence of precipitation in the local and regional water cycle as a consequence of interactions of elements of the atmosphere, hydrosphere, and lithosphere

Definition of Droughts Drought is a normal, recurrent feature of climate, although many erroneously consider it a rare and random event. It occurs in virtually all climatic zones, but its characteristics vary significantly from one region to another. Drought is a temporary aberration; it differs from aridity, which is restricted to low rainfall regions and is a permanent feature of climate.

The Nature of Droughts Drought is essentially an imbalance of the hydrologic cycle. In this cycle, water vapour enters the atmosphere by evaporation from oceans, lakes, and ground surfaces and by transpiration from plants. Water is returned to the earth in the form of rain or snow. Some of it recharges the soil moisture, some accumulate in bodies of water, and some runs off to the oceans. Thus drought can result simply from a deficiency in precipitation over a period of time, or it maybe caused by excessive evaporation and transpiration.

What Causes Droughts? Droughts are caused by a lack of precipitation in an area resulting from weak or less frequent storms and other weather systems than normal. Most major droughts last for months or years. What is considered a drought in a rainy location may be enough precipitation for another region.

Causes of Drought Lack of a precipitation High temperature, strong wind, and low humidity all of which increase the loss of moisture Shifting of normal cyclone (low pressure storm system) tracks across a region High pressure systems in which cold, dense air sinks and is warmed by compression Abnormally low sea surface temperature Human activities also contribute to the development of drought conditions; poor cropping methods and improper soil conservation techniques often contribute to create the drought.

PROLONGED LACK OF PRECIPITATION CAUSES & CONSE-QUENCES PROLONGED LACK OF PRECIPITATION LOSS OF SOIL MOSTURE LOSS OF CROPS DROUGHTS DEPLETION/POLLUTION OF GROUND WATER LOSS OF VEGETATION LOSS OF USE OF AG. LAND

Drought can also reduce water quality, because lower water flows reduce dilution of pollutants and increase contamination of remaining water sources. Common consequences of drought include: Diminished crop growth or yield productions  and carrying capacity for livestock Dust bowls(an area of land where vegetation has been lost and soil reduced to dust and eroded, especially as a consequence of drought or unsuitable farming practice., themselves a sign of erosion), which further erode the landscape Dust storms, when drought hits an area suffering from desertification and erosion Famine due to lack of water for irrigation

Habitat damage, affecting both terrestrial and aquatic wildlife Hunger, drought provides too little water to support food crops. Malnutrition, dehydration and related diseases Mass migration, resulting in internal displacement and international refugees Reduced electricity production due to reduced water flow through hydroelectric dams Shortages of water for industrial users

Where Do Droughts Occur? Areas that have frequent and severe droughts are shown on the map as the darkest shaded areas, and less sever droughts are the lightly shaded areas.

According to the study, during 1870-1900s, there were very few droughts, followed by droughts once in three years during 1900-1930 and once in 15 years during 1930-1950. There were 10 drought years during 1950-1990. Since 2000, there have been five drought years: 2002, 2004, 2009, 2014, 2015

They usually are most severe around the 30° latitudes, where dry, cool air is falling. Asia, many African countries (i.e. Kenya, Ethiopia, Somalia), are most often affected by droughts Humid areas are prone to short term droughts, whereas arid regions are prone to long term droughts

Key Drought Indicators Climate variables (e.g., precip., temp.) Reservoir and lake levels Soil moisture Ground water Snow pack Stream flow Vegetation Forecasts As a drought persists, the conditions surrounding it gradually worsen and its impact on the local population gradually increases.

People tend to define droughts in three main ways: Meteorological drought: is brought about when there is a prolonged period with less than average precipitation. Meteorological drought usually precedes the other kinds of drought. Agricultural droughts: droughts that affect crop production or the ecology of the range. This condition can also arise independently from any change in precipitation levels when soil conditions and erosion triggered by poorly planned agricultural endeavors cause a shortfall in water available to the crops.

However, in a traditional drought, it is caused by an extended period of below average precipitation Hydrological drought: is brought about when the water reserves available in sources such as aquifers, lakes and reservoirs fall below the statistical average. Hydrological drought tends to show up more slowly because it involves stored water that is used but not replenished. Like an agricultural drought, this can be triggered by more than just a loss of rainfall

EFFECTS OF DROUGHTS PRIMARY EFFECTS: Primary effects of drought result from a lack of water. As a dry period progresses and water supplies dwindle, existing water supplies are overtaxed and finally dry up. The primary losses are loss of crops low of livestock and other animals, and loss of water for hygienic and drinking

SECONDARY EFFECTS: As water supplies swindle and crops and fodder are depleted, families begin to migrate in search of better grazing lands for their herbs or move to cities to seek jobs and alternative sources of income. The migration may, in itself, contribute to spreading the scope of the disaster, especially if grazing animals are moved with people. If drought is long term, it may result in permanent changes of settlement, social, and living patterns Major ecological changes, such as increased scrub growth, increased flash flooding and increased wind wing erosion of soils.

Destruction by Droughts Droughts cause major damage to crops and animals, especially if they occur during the region’s growing season. During a drought not enough water is provided to support living things. Crops can decrease 10%-20% during a drought. Droughts affect reservoirs, water supplies, water tables, and topsoil. Water levels drop, and topsoil becomes dry and less favorable to plants. Areas that are in a drought are more likely to have wildfires than other regions.

Strategies for Drought Protection, Mitigation or Relief include: Dams - many dams and their associated reservoirs supply additional water in times of drought. Cloud seeding - a form of intentional weather modification to induce rainfall. Desalination - of sea water for irrigation or consumption. Drought monitoring - Continuous observation of rainfall levels and comparisons with current usage levels can help prevent man-made drought. Careful monitoring of moisture levels can also help predict increased risk for wildfires

Land use - Carefully planned crop rotation can help to minimize erosion and allow farmers to plant less water-dependent crops in drier years. Outdoor water-use restriction - Regulating the use of sprinklers, hoses or buckets on outdoor plants, filling pools, and other water-intensive home maintenance tasks. Rainwater harvesting - Collection and storage of rainwater from roofs or other suitable catchments. Recycled water - Former wastewater (sewage) that has been treated and purified for reuse. Transvasement - Building canals or redirecting rivers as massive attempts at irrigation in drought-prone areas