Monday, April 14, 2008

Drought for thought

Photo credit: Jon Sullivan

When I was in graduate school, we spent some time discussing natural disasters and their impacts on humanity. I was surprised to learn that drought was considered to be a significant natural disaster. In the United States, yearly drought-related costs are higher (on average) than flood and hurricane-incurred costs combined. (source: Drought for Kids: Comparison of Droughts, Hurricanes and Floods by the National Drought Mitigation Center of the University of Nebraska-Lincoln)

What is drought? Simply put, a drought occurs when there is a substantial lack of rainfall in a given area, enough to negatively impact people, plants, and animals.

The definition of drought, however, is unique to a given location. What would be considered a drought in the wetlands of southern Florida, for example, would be considered an abundance of rainfall in the United States’ desert southwest.

There are a couple of factors that make coping with drought challenging. For one, by the time that you realize you are in drought, it’s already begun. Pinpointing when a drought first starts is nearly impossible, although groups like the United States Geological Survey do an admirable job of searching for signs of trouble. (Among other things, the USGS monitors the flow of water in streams and rivers. Low flow signals a possible drought-related problem.)

Once you realize that you are in a drought, no one can say how long it will last. Rainfall models can only tell you so much. For city planners and others who regulate water flow, it can be difficult to decide when and how to moderate water intake. Imposing water restrictions, ironically, can make a drought situation worse if panic ensues and people begin to hoard water. UNL’s National Drought Mitigation Center describes the challenge of managing drought as "The Hydro-Illogical Cycle".

In the United States, the U.S. Drought Monitor keeps track of drought conditions. One place to check on world-wide drought situations is NASA’s Earth Observatory Natural Hazards: Crops & Drought.

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