Drought is a natural phenomenon caused by abnormally low precipitation over a long period of time. We learned in the Water Cycle and Weather lessons that changes in wind patterns that move clouds and moisture can cause a region to not receive its normal amount of rain or snow for a long period of time. For example, when the jet stream blocks or takes a different route in the atmosphere, that can prevent thunderstorm activity and rainfall over a large area. Other factors that can lead to drought include hot conditions that promote warm core ridging, air masses that have a high percentage of reflected sunlight, and low surface evaporation rates.
Drought has many impacts on people, animals, and the environment. Some of the most immediate impacts are economic: for instance, when farmers’ corn crops die due to drought, that could drive up the cost of corn at the grocery store. Other effects are more long-term: dry conditions encourage wildfires that burn remaining vegetation and endanger homes. They also increase air quality problems like chronic lung diseases. The reduced flow of rivers and lakes can expose more sediment, ash, charcoal, and woody debris to the surface, which reduces oxygen levels in the water for fish and other aquatic life.
Many people rely on groundwater supplies, and when those run low due to drought, they’re at risk for infectious disease from viruses, protozoa, and bacteria. When water levels in lakes drop, recreational activities are less accessible and there is a higher risk for drowning.