Drought is a problem facing many parts of the world. It is a normal climate event that occurs from time to time; however, the cause is often not “natural”. Drought is often confused with aridity. Aridity is a permanent climate change, whereas drought is recoverable. According to the National Drought Mitigation Center, drought is defined as:
Defining drought is therefore difficult; it depends on differences in regions, needs, and disciplinary perspectives. Based on the many definitions that have appeared in the literature, for example, we might define drought in Libya as occurring when annual rainfall is less than 180 mm, but in Bali, drought might be considered to occur after a period of only 6 days without rain! In the most general sense, drought originates from a deficiency of precipitation over an extended period of time, resulting in a water shortage for some activity, group, or environmental sector.
Environmentalists and scientists are concerned climate change is causing severe drought conditions, especially considering “human beings often exacerbate the impact of drought.”
Necessary to mitigate the negative effects of drought, drought monitoring gives governments, citizens, and organizations valuable information for taking action in “advance of a drought to reduce its long-term risk.” The following five drought monitoring resources are available at the National Drought Mitigation Center, along with many more.
- Drought Impact Reporter: This map graphically reports the number of impacts agriculture, fire, water/energy, social, environment, or other impacts that have been caused by drought. You can click on a state to view the impacts reported by each county. Users can also submit drought impacts to the site, which will be verified by a Drought Impact Reporter.
- US Seasonal Drought Outlook: This map is provided by the Climate Prediction Center at the National Weather Service. It “depicts large-scale trends based on subjectively derived probabilities.” On the map you can find out if drought conditions are expected to worsen, persist, improve, or likely develop in a region.
- US Drought Monitor: This is another clickable map that lets you select your region to view if current droughts ranges from abnormally to exceptionally dry. You can also compare the current map to previous maps.
- Vegetation Drought Response Index: VegDRI maps are produced every two weeks and “integrate satellite-based observations of vegetation conditions, climate data, and other biophysical information such as land cover/land use type, soil characteristics, and ecological setting.” It provides greater detail than the US Drought Monitor.
- Number of Days Since a Rain Day: This map shows the number of days since rainfall greater than 0.04 inch fell. The key ranges from 0 to over 25 days without measurable rainfall. Other rain maps are available that illustrate consecutive dry days and number of rain days.
Monitoring drought is important if regions will be able to “anticipate, cope with, resist, and recover from drought.” It is the first step in drought planning.