Much of the southern United States has been suffering under a year and a half-long drought, the worst drought in 100 years. Circumstances have become so dire that the Governor of Georgia has declared a state of emergency, with Atlanta faced with an 80-day supply of water. The dry trend appears to be continuing into the foreseeable future according to NOAA.
What is a drought?
Drought is an extended period time when a region experiences a lack of water. It can occur in nearly all climate regions. It is a temporary departure from normal conditions which distinguishes it from the concept of aridity. Aridity is a permanent climatic feature of a region that always experiences low precipitation. Drought can result in dire environmental, economic, and social consequences.
There are several ways to characterize droughts, depending on the perspective of a particular discipline of study (NDMC ). A meteorological drought is usually defined on the degree of dryness compared to the “normal” precipitation and is therefore region specific. Counties in Georgia and Alabama are averaging 5 to 15 inches below normal.
An agricultural drought links the characteristics of meteorological and/or hydrological drought (e.g., low precipitation, soil moisture deficits), to impacts on agriculture (low yields). The USDA declared 149 of Georgia’s 159 counties as primary natural disaster areas and nine more as contiguous disaster areas. To receive a disaster designation, a county must have incurred a loss of 30 percent or more in dollar value for all crops, or of a single crop or group of crops.
Withered Crops (Courtesy Lawrence Livermore Labs)
A hydrological drought refers to the effects of low precipitation (whether rain or snow) on surface (i.e., stream flow, lake levels) or subsurface water supply (soil water reserves, ground water). Hydrological droughts are often out of phase with meteorological droughts. The effect of drought on elements of the hydrological cycle like lakes and soil water often lag behind that of a meteorological drought. The noticeable effects of drought on the components of the hydrologic cycle vary. For example, the lack of precipitation is readily noticeable by a farmer but the effects on reservoir levels on hydroelectric power generation or recreational activities may take somewhat longer to be felt.
A socioeconomic drought occurs when the demand for an economic good exceeds supply as a result of a weather-related shortfall. For instance, precipitation supply may not be sufficient for the consumptive demand (e.g., hydroelectric power generation, forage, fish). Carpet makers, landscape businesses and textile factories in north Georgia are laying off workers as water for their industries continues to diminish. Increasing population and per capita consumption is creating increasing demand for resources. Thus socioeconomic droughts may become more prevalent in the future as increasing demand exceeds a unpredictable resource supply like precipitation.
TPE Links – The Hydrosphere